text:
How do I fix this strange effect that happens when I start animating items that are set to cloth in physics?
When I animate my mesh I'm building, the cloth parts start to look all funny.  I was wondering if this is normal or if there is a way to fix it?

Are you using a solidify modifier? if so, move the cloth sim modifier above that.

That fixed it, thanks! do you want to add that as the answer so I can approve it?

The problem is that your Solidify modifier is above the Cloth modifier:

This means the cloth simulation will use that double layer of geometry, which can cause some instability and self-intersections.
In your case, the inside layer is poking through the outside layer and causing shading issues due to the fact that the normals of the new outside layer are facing the wrong way:

The easiest way to solve this is to move the Solidify modifier below the Cloth one, so that the cloth simulation happens before the second layer of geometry is created:

However, if for some reason you need to take the solidified geometry into account for the cloth simulation, keep the Cloth modifier at the bottom and make sure Self Collision is enabled and uses a high enough quality to avoid instability:


text:
How do I get hair to follow the rig?
I created a model with make human and added hair via the emitter tool.  I added clothes and rigged the person with pitchipoy.  Everything seems to be moving right except for the hair.  While animating the object the hair stays in place, shouldn't it follow the emitter and the bones?  Or do I have to add bones for the hair somehow as well?

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


text:
Why is my texture rendering in a different position than it shows up when in texture view?
I made a UV map and an eye texture based on the map and attached the texture to the eyeball.  I decided to just put the image on the object without using a UV map node because I heard that blender will now unwrap the images correctly if you have a UV map for the object.  I then went into material mode and low and behold the image was placed correctly on the object.  Then I decided to do a test render and the image shrunk around the object and I am curious as to why it renders differently than it appears in material mode, and what I can do to fix it?  Do I just need to use the UV map node?  BTW, I'm using cycles render engine.

could you please post your blend file? something is strange here indeed.

Yeah, I have really shauty internet, but I should be able to post it tomorrow.

By default, Blender uses 'Generated' Corrdinates for placing textures on objects when rendering with Cycles. In the viewport however, when you have Cycles selected as a render engine, the texture node which is selected will be previewed on the object using the currently selected UV map. That's why you see it mapped correctly in the viewport, but mapped in a different fashion in the rendering.
Now I don't know why you were told that Blender would not unwrap correctly using the UV map node, but anyways: Use either a Texture Coordinates Node and plug the UV output to the 'Vector' input. This will use the UV map from the object which is currently marked as 'renderable' (yellow circles in screenshot). Or, you use the UV Map node. Here you can choose the name directly, but remember that if you rename the UV Map later on in the mesh data, you'll need to update the input field in the node as well (red circles).

By default if object has no UV maps it will use Generated coordinates. If it was unwrapped, by default Cycles will use that UV map. Doesn't matter if that UV map was plugged into the Vector input of texture or not.

hmmm true, didn't know that. Thx for clarification.

I'll try this tonight and see if it works, Thanks!

This worked, thanks!  I never realized that the material view didn't necessarily show the image accurately.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Importing Mixamo's FBX in Blender
I'm trying import the character with the animation and it gets scrambled, I tried a lot of settings but in the end, none of them worked. Other editors like Unreal's Engine Editor can import the file without any problems.
The file can be downloaded in here:
https://www.dropbox.com/s/i20wfur8e34i3a2/Sword_And_Shield_Slash.fbx?dl=0
Here's what happen when i try to import:

I also experienced this weird stuff and I was able to solve it.

Select the distorted object
Select Object Tab from Properties Window
Change Transform scale to 0.01
Change Transform X-axis to 90 degrees

Result:
https://www.dropbox.com/s/1yip15gm13dke1c/COnverted.blend?dl=0

Option 2: You may refer to this link if you don't want to do it manually. http://growlybearproductions.com/Blender/
Option 3: You may also change fbx import settings like this (Blender 2.76b)

I had this problem and managed to fix it by doing this. First you need to scale your model correctly to the size you want in Blender Then while in object mode press a to select all and then press "ctrl + a" and apply scale, rotation and location. Then export your model as an .obj Import it into Mixamo animate it and then export it as a .dae. Then import the .dae into blender Re-scale the model to what you had it as before and then it should work


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Blender shut down while exporting psk/psa file
I'm a Blender newbie and all I know about it is what you can find in YouTube-Tutorials. Now I have the problem, that I have to export a .psk/psa file from Blender (2.75a) and every time I try it, Blender stops answering and crashes.
It is a makeHuman file imported in Blender, that I animated with the Dope sheet and the NLA Editor. In the tutorials, they say, that I have to set the cursor into the center (0/0/0) and the scale to (1/1/1) and so I did. I also joined the seperate Meshes of the body, hair and cloths, to have only one mesh parented.
Can anybody help me to create a .psk/psa NPC without crashing Blender?
Thank you very much.


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How to rotate an object by a special axis, without changing the shape
I want to swing this triangle around on that green axis.

or some way of accomplishing the same thing.  I just need to flip the triangle on its longest side.  as you can see me attempting to do in this gif animation.

I haven't found a way of doing it without distorting the shape of the triangle.
and I don't want to just eyeball it by trying to pull the corner into place.
I want it to be exactly the way it was only flipped.


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Does the steam version of blender install Python automatically?
I'm not really having any problems.
I've just recently downloaded "make human".
on the download page it says it needs Python installed to work.
I haven't installed Python but it seems to work anyway.
And I'm assuming that's because Python must be bundled with the steam version of Blender.  because the version of blender I have was installed through the steam client.
If that wasn't already apparent.

Python is bundled with all versions of Blender, since 2.5 onwards. Many aspects of the UI are declared in python and it is therefor an integral part of the UI system (shipping without would be a world of hurt).
According to Make Human docs the add-on comes with its own version of Python ( 2.7 ).

(...) there is a bundled python inside the build zips (...)

This means you have at least two versions of python on your machine, one that Blender uses and one that Make Human uses, that's OK.

All the full releases of MakeHuman come with python in them already. You don't need anything additional to run them. You would only need to install Python on it's own if you were trying to build the pure python branch from source.
I do not think any version of Blender installs Python for you.


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How do I get rid of a random semi-circle on floor that shows up after scene is rendered??
There is an annoying shadow that is showing up in the middle of the floor after I render the scene! I have no idea where it is coming from. I am new at this, and just trying to change the materials on the floor. See image (bottom render) att

could you upload your blendfile?

Is "that shadow" affecting only the floor material? Could you post its material node?

It would really help if you could upload your .blend file to Blend-Exchange and post the link in the question.

thank you so much for offering to help! somehow the shadow disappeared. I'm sure it will come back again, at which I will have to re-post and will add the link next time.  thanks again!

@user16320 Okay :) In that case I've closed this question. BTW, my guess is that this might be cycles's form of z-fighting, where two floor meshes are in the same place.


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How to automatically/dynamically repel control points on a path/curve?
I am trying to generate a 3D path which will be then object-bevelled with a circle. The aim is to make some sort of spaguetti. The problem I face is that once I extrude my circle along the path, (as expected) the 3dimensional knot crosses itself.
Is there a way to automatically repell the control points in such a way that once the extruded shape goes along the path, there won't be crossing-over?

I don't think this is possible, at least not right out of the box, I don't know if there's a script already made to to that.

If all the control points are the radius of the bevel circle apart, then an iterative script that moves any non neighbouring control points that are within r of each other... yes as I see you have written in a comment on @DFR answer.

Yes, it looks like a relatively trivial issue but on a second thought it grows up a bit. Given your suggested method or mine, at some point some more sophisticated algorithm must be implemented. Of course, it would all depend on the size of the curve.

There is no built in tool to do this automatically, nor any specific tool to do what you want. I don't think blender as any sort of curve intersection tool, let alone one that takes bevel objects into account.
That being said you could use a few other workarounds.
Either select all your intersecting vertex and scale them out relative to the selection center. That should move them apart eventually enough to avoid all intersections, or
You could use Proportional Editing for more localized control, to move only vertex within intersection radius. Select one vertex with close-by intersections, press O key to turn Proportional Editing on then scale it up. Control the influence radius with the Mousewheel to affect only neighbouring vertex in the desired influence area.

Ok, thanks for your reply. I can then focus on working a script where I draw a curve taking care that the coordintate-generation function positions them far enough (based on the bevel object radius) on the x,y,z. Or something on that line


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Is there a way to hide the path that a hook modifier draws on the 3D view?
I have a scene with an absurd amount of hooks (on the order of thousands). This, of course, clutters my scene quite badly.
I was unable to find a way to hide the paths that hooks show linking the parent to the child. I could of course just make it invisible but then the effect of the modifier is lost.

Possible duplicate of What are these block dotted lines?

Those paths are called 'relationship lines', and can be toggled on and off here:


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Model looks different in game engine
I'm a little new to Blender and I only have very basic experience with the game engine.  One thing I noticed is that some models look way different in game than in the editor window. For example,

This doesn't happen on all models, just some of them. This model was created by Sega, so I wouldn't think there would be any errors with it. Does anybody know what's going on here?

Is the scale applied to all the objects?


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Cycles. Masking shader. How to make objects disappear in plain sight.
So I have a scene. I want to slide out a text, for example, as if it was hiding behind an invisible wall. I know that you can achieve this effect with a boolean modifier... but I can't use it in this case. Plus to make it happen with a text you need to convert it into a mesh first - no good.
How to make so that when an object, partially or completely, is inside another object that this makes that part invisible? (The other/masking object is completely invisible all the time, of course)
I sense that it has something to do with a clever Light Path and Mix Shader nodes arrangement.
(Made with a boolean modifier)

To achieve this with nodes... Something along the lines of this?

How it looks in the viewport:

Final:

Nodes:
For Masking Object - cube in this example just use Transparent BSDF with pure white color.
For object being masked - text - use mix between chosen shader (Diffuse here) and Transparent by Light Path > Transparent Depth:

Of course object being masked should be inside masking object.

Exactly what I was looking for. Thank you.

Pretty clever solution, nice answer

Can i have a graduated edge or fall off to the mask?

You could also do this with render layers using mask layers.


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Imported CAD .stl models behaves "strangely" with the modifiers
I have stumbled upon the following problem:
1) I import into blender an .stl file exported from the AutoCAD (even relatively simple model - something like cube with rounded corners i.e. dice)
2) I try to apply a Boolean modifier on it and an another mesh (created directly in blender), for example a cylinder, then I test every possible operation, i.e. dice union cylinder, dice intersect cylinder and dice minus cylinder.
3) the resulting object seems to be a result of the operation OPPOSED to the selected, that is:
3a) if I choose "union" then the result looks like "difference" (dice with part of cylinder removed)
3b) if I choose "difference" then the result looks like "union" (dice and cylinder together)
3c) if I choose "intersection" then the result looks like cylinder minus dice (sic!) (cylinder with the part of the dice removed).
It looks like the blender treats the dice as being everywhere EXCEPT the dice itself (a set complement to the dice). It is strange, because the normals seems normal ;) i.e. they point outwards from the dice surface (in N-menu I choose to show normals). Have anybody seen such a issue? Is there a way to "fix" this? Anybody knows what is the purpose of this?

Have you tried recalculating the normals?  I know they look ok, but sometimes even one face being off can cause weird results.

Also you can hit Ctrl+A and apply its loc,rot,scale. This ussually works for .dae at least.


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Is it possible to have Blender render rays of light that fade away?
I was wondering if it's possible to have Blender render visible light that fade away the farther it gets from the light source in Cycles render?

That's definitely part of what I'm looking for, is it possible to use that process with something like this where you can see like say, a distinct cone of light before it fades away?


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printable keyboard shortcuts
Is there a good printable keyboard shortcut sheet (that looks like a keyboard) for Blender 2.75? I found a really nice one here: Blender 2.4 Hotkeys, but that was created for version 2.4 in 2005... and 10 years is a long time to not update key bindings/interface. Is it still good or is there a nice, printable (aka won't kill an entire ink cartridge) version somewhere else? A Google search doesn't really give me anything above 2.6 or that's economically printable.

while I have attempted to give some form of response below, the question borders on off topic for blender.stackexchange or should maybe be addressed in the Resources for Blender thread

Not exactly printable, but you might be interested in this interactive one.  It may be more convenient given the context sensitive nature of blender's shortcuts. There is an also an addon in contrib which can auto generate SVG representations of the current keymap.

is https://wiki.blender.org/uploads/1/14/Keyboardlayout_250.png no good printed in greyscale / low quality?

Alternatively tufts has a nicely compiled (but incomplete) list of shortcuts per area:   http://ocw.tufts.edu/data/71/1717950.pdf
The tufts shortcuts might be handier as it doesn't try to cram all info onto a few keys which change depending on mode anyway. Unfortunately it doesn't list some of the more useful key combos ( vertex-slide Shift + V)

shortcuts (hotkey) & Charts for Blender
https://www.katsbits.com/tutorials/blender/useful-keyboard-shortcuts.php

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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How to open the Manage Unused Data window using python code?
I'm new to Blender python. I would like to open the "Managed Unused Data" Window by using a button. Why is the function below not working? I've already added a button that can execute the class, but nothing happen. If I use the main menu in blender, all works and the window opens. I took the phyton code from there ( bpy.ops.outliner.orphans_manage() ) . Why is it impossible to open the window in my snippet?
Any help? Here's my snippet:
# Manage Orphan Data
class CWTools_PurgeDataManager(bpy.types.Operator):
    bl_idname = "object.cw_tools_purgedatamanager"
    bl_label = "Manage Purged Data"
    bl_description = "Manage all unused data"

    def execute(self, context):
        bpy.ops.outliner.orphans_manage()
        return {'FINISHED'}

This is the window I would like to open with the code above.

After a bit of trial&error I found that you must call the operator with the special INVOKE_AREA parameter.
import bpy
bpy.ops.outliner.orphans_manage("INVOKE_AREA")

Link to the docs
BTW you don't have to define an override operator if you just want to open this window in your custom operator execute. You can force the operator context inside your layout. Just bear in mind the entire layout will have this context. You can set it back to exec default afterwards.
def draw(self, context):
    layout = self.layout
    layout.operator_context = 'INVOKE_AREA'

    layout.operator("outliner.orphans_manage")

    layout.operator_context = 'EXEC_DEFAULT' # Back to "normal"

# Alternatively :
def draw(self, context):
    layout = self.layout
    row = layout.row()
    row.operator_context = 'INVOKE_AREA'
    row.operator("outliner.orphans_manage")
    # layout.operator_context is untouched

Thank you a lot. The "INVOKE_AREA" option was the solution. Works great!

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Geometry Nodes: Is it possible to rotate a point?
Is it possible to rotate a point or points in geometry nodes? I mean before using the points to place instances on them? I know how to rotate instances.
But would the animation framerate increase if you rotate points first instead of rotating instances later?

To answer your first question: A point has no size and no rotation. But you can assign any attributes to a point.
Depending on how you use these values in your setup, you can do this with the  Capture Attribute or Store Named Attribute nodes, for example.
The basic rule here is: Use Capture Attribute if Store Named Attribute is not absolutely necessary, otherwise you would store additional data in the geometry that is no longer needed in the end and would only fill up the memory.

To answer your second question: This depends on your setup.
If you compare both scenarios in the simplest case, there is really no difference in terms of performance.

(Storing the rotation as attributes in the point domain before instantiation)

(Transforming the objects after instantiation)
However, it can become significantly more computationally expensive under certain circumstances if, for example, you first instantiate objects at the points, then realize the objects and then rotate the mesh. So it really depends on your setup which approach is more performant.
Therefore, the general rule is: If possible, apply any processing to those parts of your geometry that are structurally decisive for your final result at the beginning and that occupy little memory.

Thank you. So basically realising geometry and transforming it later increate the calculation rate. Doing it before this steps keeps everything basically faster.

There is no built-in attribute for such use case. You just need to store some named rotation on points.

Hi, thanks for the post. This site is not a regular forum, answers should be substantial, stand on their own, and thoroughly explain the solution and required steps. One liners and short tips rarely make for a good answer. If you can, [edit] your post and provide some more details about the procedure and how it works, perhaps add a few images illustrating some steps and final result. See How to write a good answer?, otherwise it may be converted to a comment.


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Array modifier not working as expected
I'm trying to create a car rim in Blender. However when I try to add array modifier, and rotate the instances around empty, they are not in the same distance from the center (as shown in the image). I can't figure out, how to put them in the same distance from centerpoint and I haven't found a satisfying answer. Thank you in advance.

How to use array to create circular array without spiralling, Array Modifier Rotation Problem, Multiple array modifiers and object offset rotation and How to make a circular array using offset object as center? are all relevant to your question.

Unless you specifically need the driver for the relative offset, turn off relative offset and remove the driver.
The Object Offset doesn't work the way you're expecting it to. The second item in the array will be moved the same distance from the first item, as the first item is from the empty. The second item will be rotated as many degrees from the first, as the first is from the empty.
So, to get the effect you want follow these steps:
NOTE: Even if the origin of your rim "piece" is already supposed to be at the center of the rim, these instructions will be the same. You'll just have a few things on top of each other.

Set the array "Count" to 1 (just for now)
Place the first element on the rim exactly where it should be
Place the empty in the exact same location as that element, with the exact same rotation as the element
Place the 3D cursor at the EXACT CENTER of your existing rim
Change your pivot center to "3D Cursor"
Select the element (without selecting the empty)
Set your array count to the number of elements you want to end up with (5, I think?)
Then rotate just that first element and the rest will project ahead of it
Adjust until the desired effect is achieved
???
Profit

Hope that helps!


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Extend Video Strip in VSE
In older versions of Blender I was able to extend a video strip in VSE using the triangle at the right end. In this case the last image stayed visible. But in the current Version, this is no longer the case. But for me, that was a nice feature. Can someone help me?

The freeze-frame at either the start or end of a strip only occurs when you reach the limit of the source media. You can fake this by adding a Hard Cut using ⇧ Shiftk. Then drag the strip end as usual.
The over-extended area of the strip will be shaded grey and show only a still frame. If it flickers, then click the Refresh Sequencer button at the bottom of the timeline.

I dont know that feature. But I would solve that by just rendering out the last image and then save it. That image I would put at the end of the video sequence. But there might be an addon for this.

That's my current work around. But before it was just much easier.

I use that feature a lot with my current version 2.77a, a version I'm quite happy with.  I usually avoid upgrades until the bugs are ironed out.

As of more recently (tested in Blender 4.2.1) you can use the Move/Extend from Current Frame E feature.
Select your clip to extend, press E, then move the mouse to the right to choose for how long to hold its final frame.

The question seems to be more about the holding frame that happens when overextending. In which case, the accepted answer is still the right one.

Ah, that's very possible. And it turns out you can just click the strip's end to reveal handles, which allow you to extend it without even using E, so maybe that's what the original author was using. Oh well!


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Moving objects whilst in animation
I would like to make a collision with two objects whilst freely moving once object over the other in real time. Is there a way to do this in Blender?

This isn't possible outside of the game engine, but within the BGE, you can interact with objects quite easily. You can set up your objects in Blender Render, but the physics are a little different in the BGE so it's better to just work in the latter.
Start by setting up your objects and their physics properties. Then open the logic editor and set up either keyboard or mouse sensors for the moveable object (make sure it's selected) and attach the sensors to motion actuators. Set up the actuator's appropriate fields to tell it which way to move the object and how fast. That's about all there is to it. You can now start it as a game by putting the cursor in the 3D viewer and pressing P, then use your keys to move your object around.

Thanks Anthony. I have tried the above, however the problem I am having with the BGE is that when I am in play mode I can't seem to be able to move the view at all whilst moving the objects. Is there a way to move your view point after you press P? Thanks in advance

You have to set that up with logic bricks to control the camera.


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Instance a rigged mesh
I am trying to create a reusable rigged mesh, specifficly a toggle switch.
What I want to achieve is multiple switches that can be posed and animated separately but that share mesh data so I can go back and make changes.
My current set up is the toggle switch in a separate scene in the same blend file being brought into the scene as a collection instance. The only way to pose this that I have found is to change it in the instanced collection, which changes every instance together.
I have also tried putting the collection in a separate .blend, linking the collection in and adding a proxy to it's armature. Though it created an unnecessary amount of overhead (extra file, having to create the proxy) it did work for the first instance, however when I tried to repeat the process to add a second instance both got stuck in the default pose. I have found multiple older posts saying that the way to fix this is to create a duplicate of the source .blend for each instance, however this does not solve my problem because I still can't make changes to the mesh and have my all my instances updated.
One idea I have had is to somehow be able create a collection instance and have the rig be controlled using custom properties on the instancer, however I am yet to find a way to set that up.
This seems like such an obvious thing to be able to do that I feel sure I am missing some basic facet of reusing meshes.

I have found that when I create a collection instance of a collection containing a single mesh linked to an armature and make instances real it creates a duplicate armature and a new object linked to the original mesh, allowing the mesh to be animated separatly from other copies while being updated together.
To clarify:
Add your armature and rig to a collection
Create a Collection Instance of that collection (Shift+a > Collection Instance)
Make the instances real (Ctrl+a > Make Instances Real)


text:
How to lock vertex to axis during bone rotation?
I am very new to bones, and something I haven't been able to figure out is how to constraint vertices to certain axis.
Consider the following:

This is a simple model with some bones I added. Now, See what happens when I rotate the two middle bones:

I have circled where there is an undesirable deformation. What I would like to happen (but for these two bones only) is for the vertices to be constrained along Y. Basically, I want the vertices to slide along the edge, not rotate around the pivot. Everything else about this is fine to me; I just need the vertices along the edge that are connected to these bones to never move inward (or outward for that matter).
What are some ways to accomplish this?

Consider setting the deforming bone option Relation Parent [Inherit Rotation] False as depicted below.  The bone will still be moved by parent movement.

Here a parent bone is rotated.  Parent bone set to [deform] False.  This is an attempt to emulate your images in the question.

Below a bone constraint.

You can restrict bone axis movement.  In general restrict bones rather than vertices.
The default armature automatic weights were accepted.  Weight paint mode below.

The vertex density supports the curved images.

Thank you for such a detailed reply! Unfortunately, I was unable to apply any of this successfully. I'm hesitant to use constraints as well, because I ultimately will be manipulating these bones in a game engine, and I am unsure the constraints will carry over.


text:
Why is the viewport DoF glitching?
When I try to use the viewport DoF the viewport just seizes up and when I try to zoom in and out I get this effect, could this be due to an outdated gpu? I'm using Blender 2.76, this was happening with 2.75 as well.

What GPU do you have?

ATI Mobility Radeon HD 4200 series

I tried enabling the settings I saw in your screen shot (Focus:Empty, Composition Guides?, F-stop 2.8, Imperial measurement units) but I couldn't reproduce it. Might help if we could take a look at the .blend, even if you simplify it by removing objects, etc. Also, does the glitch persist even after you Load Factory Settings? This might be the kind of thing to file directly in a bug report.

The glitch still occurs after loading the factory settings. Also, this happens with any .blend, even if it's just the default scene so I don't think that it's a problem with the .blend. It may be my GPU's compatibility, I do have a fairly outdated GPU.


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Vertices Selection Problem
Whenever I try to select multiple vertices in edit mode using control-right click it doesn't work. What do I do? I have tried other keys but nothing has worked.

By default Shift is used to select multiple vertices.

Well I need it to connect the edges thought the vertices

it works for me, are you absolutely sure that the vertices are connected?
try moving around all intermediate vertices, there could be an isolated vertex (even if it seems to be connected)


text:
How to keep UV set position while moving an object?
I would like to keep a UVset position in the world coordinates while moving my object.
So the texture have to stay in place in the world while the model moves.
How do I make this?
Thank you
Chris

How does your object or texture look like? is it a simple plane? I may have a solution by you must give some details

You can map your texture using another object. If you move the one with the material, the texture will stay still. If you move the 2nd object, the texture will move.


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How to compose alpha information on a render result with transparency?
I would like to compose in Blender a very simple result (actually simple...)
Attached you see what I have.
How to do this in Blender?!
Thank you in advance.
Chris

I think the Alpha Over node will do what you want?  Here are some quick results:

Exactly what I was looking for. Thank you! I was shure I've tested this combination already... but no matter.


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Move particles first and stick to texture target
I would like to form particles to a logo.
I would like to let balls fall to ground and THEN move them to form a logo. The logo is controlled by a texture.
Is it possible to move particles to a texture target and distribute in the logo area?
I've made some tests with a texture force field but it doesn't work like expected. Maybe I misunderstand something here.
Thank you in advance
Chris

The Texture force field isn’t how it sounds - it’s actually a means of having fine control over the vectors within the force field by using the RGB colors a bit like a normal map with 0.5,0.5.0.5 being no force and +/- that being strength in each of the XYZ directions - rather than being a force that acts towards a texture.
Probably the best solution would be to create your logo out of geometry (rather than an image - or hidden geometry that sits behind the actual image) and give this a force over its entire surface to attract to the logo, keyframing the force strength to activate it at a specific frame.
This can achieve something like the following :

The 'Text' logo includes a Force forcefield (set to Surface) - initially keyframed to zero strength.
Once the particles have fallen and collected on the floor the gravity field weight is keyframed down to zero (to allow the particles to float) and the Force on the logo is increased to a large negative value to draw the particles. A Drag forcefield slows down the particles to prevent them getting out of hand.
As the particles get closer to the logo the Force can be further reduced to allow the particles to settle down.
Blend file included


text:
How to change the grid snapping values for every axis individual?
I would like to change the grid values per axis, to get individual snapping values direction constrained.
Current situation for a grid in blender:
Scale for x,y,z = 1 (Objects moves using value of 1 in every direction, when snapping is on.)
I would like to set the follwing values f.e.:
Scale for x,y,z = 1, 1, 0.5
So the object would move per 1 unit to x and y, and 0.5 units upwards (z-axis).
Is this possible?
At the end I would like to set the grid individually for every axis.

I don't think it's possible.


text:
CUDA error: Launch failed in cuCtxSynchronize(), line 1372
I have the following CUDA error when trying to render my project in cycles:
CUDA error: Launch failed in cuCtxSynchronize(), line 1372

My scene rendered well some days ago. After adding new elements and models the error appeared. I had this error already some time ago, while working on this project, but after changing the content and sample amount in the render settings it disappeared until today.
I am using a GeForce 1080 Ti with 11 GBytes of Ram. The scene use currently not much vram of my graphic card. So the vram can not be the reason.
Any ideas for a solution please? Maybe some developers are reading this too.
Thank you a lot for any tips
Chris

https://blender.stackexchange.com/questions/94178/rendering-with-gpu-crashed and https://blender.stackexchange.com/questions/64615/how-do-i-fix-cuda-error-launch-failed-in-cuctxsynchronize-and-cuctxcrea and https://blender.stackexchange.com/search?q=cuCtxSynchronize

Thank you for the links. I have already seeked for a solution here in the forums, but the main problems of other users are based on low memory. As I wrote my card has 11 GBytes of Ram so mem can not be the problem.
Especially because the scene rendered already and there were some errors too before I started to add new elements.
I am using the Principled shader for nearly all materials. I guess I will replace the shader to the regular shader model and see what happen then. The new shader could be a reason too.
Do someone has any other ideas? Thank you.

I struggled with this problem for months. Used different computers, re-installed Blender, re-installed windows (I am using 8.1 & 10), installed new and old drivers for my Nvidia card, changed the TDR and everything I could think of...but no luck.
Then it occurred to me that the Gforce Experience runs in the background (and being in my opinion, not a well written program) may be overlapping the memory of Blender or at least hogging the memory. So I un-installed it and magic!!! All Cuda errors and memory errors went away. Blender works again as it should!!!
I hope this works for you, as it did for me. Unfortunately, I did not discover this for months, until I had pulled every single strand of hair out of my head.

Thank you for your answer. This is interesting. I have not tried your solution yet but there is an article I have written to solve the issue even if you have GForce Experience running and don't want to uninstall it.
Here ist the link to my article: http://www.christoph-werner.de/2017/12/31/blender-fix-for-cycles-bug-launch-failed-in-cuctxsynchronize/
I forgot to mention it here.

Thank You for your reply' I can see that you are very experienced and that was a nice link to your report. For me, the TDR changes did not solve it. If I re-install "The Experience" The issue returns. Since Blender is more important to me and I can do manual driver updates, I choose to keep a functioning Blender.

Have you tried higher TDR values like I mention it in my article to increase the waiting time? Sometimes 30 seconds are far not enough. Greetings.


text:
Rotate object "Like Center Mouse Button"
(I don't even know how to articulate this).
Say I start Blender with the default 2d scene - cube and view centered at 0,0,0. I can use the center mouse button to rotate/pan around the cube. Any up/down mouse movement gives me a "pitch" with respect to local view, and any left/right mouse movement "yaws" the cube. The amount of movement is uniform no matter where my cursor is, and no matter how I have rotated the other axis. This is an easy and natural way to pan around an object.
So now I basically want my camera do to the same. The best technique I've seen is to create an empty at 0,0,0, parent the camera to that - view through the camera - and rotate the empty.
That works - but no matter what I do - I can't get the same kind of rotational control with my mouse that I had with the "center mouse button" above. I've tried everything from changing the rotate transform mode (global, local, view), locking one of the axis, and using rr for "trackball" mode.
I can almost do this if I use the gimbal in "view" mode and just move the up/down and left/right rotation handles (individually) - but the mouse behaves very poorly - like it gets too sensitive near the center of the gimbal, and stops working altogether outside of it (giving a very narrow, single-axis control, oddly-proportional control). Nothing like the two-axis control which is completely linear - even if you indefinitely move the mouse in one direction.
Anyone know how to do this?

You can move the camera exactly as your would move the viewport by just enabling "Lock Camera to View" in the view section of the properties panel (n), and then move your viewport: your camera will automatically follow.

Awesome - totally what I wanted - thanks!

I still wish I could rotate the empty as I discussed - because although I can position the camera like you said - some of the key frame interpolations aren't completely smooth when the camera starts moving around the object and rotating at the same time.


text:
How to append render layers from one scene to another?
I have two scene versions. The scene content of both are equal, but I have added some new render layers to the second version.
Now I would like to append the render layers from version 2 -> version 1.
Is this possible without append the objects?
The plugin Copy Render Layer Addon is unfortunately not working with version 2.79, that I am using currently.
Thank you
Chris


text:
Exporting UV coordinates by face elements
I'm trying to write my own export script, and I'm not sure how to reference the uv coordinates as an element array, similar to how .obj format works (ie. you have a list of all uv coordinates "vt s t" and each face selects the correct index). I looked at previous threads on similar things, but there doesn't seem to be anything similar to my issue. Do I need to hash all uv coordinates and compute the index for each face myself? Or is there a built-in way to do this? How does the .obj exporter work? Also, for further reference, is it possible to see the python source for the .obj exporter?

It would be nice if you could post your edit as an answer.

@stacker And done!

I found the .obj export source in /usr/share/blender It's probably different on your computer, the best place to see where you can find it is to go into user preference under Addons. It seems like the official exporter just creates a hash map of uv coordinates. This seems to be where the magic happens.
# Make our own list so it can be sorted to reduce context switching
    face_index_pairs = [(face, index) for index, face in enumerate(me.polygons)]
        uv = f_index = uv_index = uv_key = uv_val = uv_ls = None

        uv_face_mapping = [None] * len(face_index_pairs)

        uv_dict = {}
        uv_get = uv_dict.get
        for f, f_index in face_index_pairs:
            uv_ls = uv_face_mapping[f_index] = []
            for uv_index, l_index in enumerate(f.loop_indices):
                uv = uv_layer[l_index].uv
                uv_key = veckey2d(uv)
                uv_val = uv_get(uv_key)
                if uv_val is None:
                    uv_val = uv_dict[uv_key] = uv_unique_count
                    fw('vt %.6f %.6f\n' % uv[:])
                    uv_unique_count += 1
                uv_ls.append(uv_val)

Since I answered my own question, should this be deleted? I feel like this has some value to other people who may want to do something similar, as this is a specific and non-trivial task.

Answering your own questions is fine, you even have the option to answer as you post the question, it is a way to share your knowledge with others.


text:
How to I subdivide a mesh so that it fits into a bounding box?
This is a python question. What I want is a function that takes a mesh M and a bounding box B (This bounding box can be axis aligned or on an arbitrary angle. This detail isn't important, which ever is easier to implement, so it's okay to restrict B to be an axis aligned box if it helps) I want a new mesh M' that is subdivided so that M' fits perfectly into the bounding box B. To make it more clear, if a polygon P in mesh M is partially inside B and outside B, then that polygon needs to be split into P1 to Pn, and only the polygons inside B are returned; the rest are discarded.
I want this to be non-destructive, so M' shouldn't be added to the scene, nor should M be changed in anyway. I just want a new mesh that's not a part of the scene, so that I can export it. I already know how to split polygons by planes and implement this from scratch, however, I want to know how much of this is already implemented/not implemented for me within blender's libraries. It seems non-trivial to do this from scratch, and just using my linear algebra knowledge.

If I understand correctly, you want only the part of the mesh which intersects the bounding box? You could try using a boolean modifier

@gandalf3 yes, but in addition, if a polygon P in mesh M is partially inside B and outside B, then that polygon needs to be split into P1 to Pn, and only the polygons inside B are returned; the rest are discarded.

@gandalf3 boolean modifier seems like exactly what I want. I just need to look up the blender API for it. Thanks!

This slices a mesh object into axis-aligned parts (changing the active object):
import bpy, bmesh
from bpy import context as C

bpy.ops.object.mode_set(mode='EDIT')

bm = bmesh.from_edit_mesh(C.object.data)

edges = []

for i in range(-10, 10):
        ret = bmesh.ops.bisect_plane(bm, geom=bm.verts[:]+bm.edges[:]+bm.faces[:], plane_co=(i,0,0), plane_no=(-1,0,0))
        bmesh.ops.split_edges(bm, edges=[e for e in ret['geom_cut'] if isinstance(e, bmesh.types.BMEdge)])

for i in range(-10, 10):
        ret = bmesh.ops.bisect_plane(bm, geom=bm.verts[:]+bm.edges[:]+bm.faces[:], plane_co=(0,i,0), plane_no=(0,1,0))
        bmesh.ops.split_edges(bm, edges=[e for e in ret['geom_cut'] if isinstance(e, bmesh.types.BMEdge)])

for i in range(-10, 10):
        ret = bmesh.ops.bisect_plane(bm, geom=bm.verts[:]+bm.edges[:]+bm.faces[:], plane_co=(0,0,i), plane_no=(0,0,1))
        bmesh.ops.split_edges(bm, edges=[e for e in ret['geom_cut'] if isinstance(e, bmesh.types.BMEdge)])

bmesh.update_edit_mesh(C.object.data)

bpy.ops.mesh.separate(type='LOOSE')
bpy.ops.object.mode_set(mode='OBJECT')

The separate operator is needed, but you could write the bmesh to a new mesh datablock and temporarily bind it to a new object and run this operator. Then unlink it from the scene and delete, keeping the sliced mesh. Bmesh syntax in short:
bm = bmesh.new()
bm.from_mesh(me) # or from_object(ob, scene)
#...
me2 = bpy.data.meshes.new("Sliced")
bm.to_mesh(me2)
#...

I like this more than using boolean modifier. Thanks!

sorry, one more question. Where is bmesh.ops.bisect_plane and bmesh.ops.split_edges documented? And how did you know that 'geom_cut' are the edges that were added? I can't seem to find the behavior of these functions anywhere on the docs =/

You can find it here: http://www.blender.org/documentation/blender_python_api_2_70a_release/bmesh.ops.html#bmesh.ops.bisect_plane


text:
Why is my addon so slow?
I made a Blender addon that thickens surfaces like this:

You assign the inner surface to a vertex group named InnerGroupTriangle and the outer surface to OuterGroup. The inner surface must be made of triangles. Then you run the script and the outer surface scales away from the inner surface. The script works but is very slow. I can't figure out why.
Here is the code:
import bpy

def is_edge_in_group(edge,object,group_id):
    for v_index in edge.vertices:
        is_in_group=False
        for g in object.data.vertices[v_index].groups:
            if g.group==group_id:
                is_in_group=True
                break
        if not is_in_group:
            return False
    return True

def check_if_face_in_vertex_group(vertices,group_index):

    for face_vert in vertices:
        face_vert_in_group=False
        for g in face_vert.groups:
            if g.group == group_index:
                face_vert_in_group=True
                break
        if not face_vert_in_group:
            return False
    return True

def is_vertex_in_group(vertex,group_id):
    for g in vertex.groups:
        if g.group == group_id:
            return True
    return False

def change_vector_basis_from_orthogonal(rootv1,rootv2,rootv3,vector_to_transform):
    px=vector_to_transform.x
    py=vector_to_transform.y
    pz=vector_to_transform.z
    x1=rootv1.x
    y1=rootv1.y
    z1=rootv1.z
    x2=rootv2.x
    y2=rootv2.y
    z2=rootv2.z
    x3=rootv3.x
    y3=rootv3.y
    z3=rootv3.z
    #print(rootv1,rootv2,rootv3,vector_to_transform)
    try:
        a=(pz*(-(x3*y2) + x2*y3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (py*(x3*z2 - x2*z3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (px*(-(y3*z2) + y2*z3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3)

        b=(pz*(x3*y1 - x1*y3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (py*(-(x3*z1) + x1*z3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (px*(y3*z1 - y1*z3))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3)

        c=  (pz*(-(x2*y1) + x1*y2))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (py*(x2*z1 - x1*z2))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3) + (px*(-(y2*z1) + y1*z2))/(-(x3*y2*z1) + x2*y3*z1 + x3*y1*z2 - x1*y3*z2 - x2*y1*z3 + x1*y2*z3)
    except ZeroDivisionError:
        #print (rootv1,rootv2,rootv3,vector_to_transform)
        return (-1,-1,-1)
    return (a,b,c)

def calculate_root_vectors_and_transform_vertex(point,edge,ob,ig_polygons):

    vertices_in_edge=[ob.data.vertices[x] for x in edge.vertices]
    #print(list(vertices_in_edge))

    polygons=ig_polygons
    polygons_next_to_edge=[]

    for polygon in polygons:#finds the faces next to the edge
        edge_in_polygon=True
        for v_index in edge.vertices:
            if not v_index in polygon.vertices:
                edge_in_polygon=False
                break
        if edge_in_polygon:
            polygons_next_to_edge.append(polygon)
        if len(polygons_next_to_edge)==2:
            break

    edge_vector=(vertices_in_edge[1].co-vertices_in_edge[0].co)
    if len(polygons_next_to_edge)==2:#edge next to two faces
        second_face_normal=polygons_next_to_edge[1].normal
    if len(polygons_next_to_edge)==1:#if edge is next to only one face, condider the normal of the other face to be perpendicular to the edge and the only face's normal, away from the face.

        normal = polygons_next_to_edge[0].normal
        for edge_face_vertex_index in polygons_next_to_edge[0].vertices:#finds the vertex on the face next to the edge that isn't in the edge
            if not edge_face_vertex_index in edge.vertices:
                face_vertex_not_in_edge=ob.data.vertices[edge_face_vertex_index]
                break

        cross=edge_vector.cross(face_vertex_not_in_edge.co-vertices_in_edge[0].co)
        direction=1
        if normal.x !=0:
            if cross.x/normal.x <0:
                direction = -1
        elif normal.y !=0:
            if cross.y/normal.y <0:
                direction = -1
        else:
            if cross.z/normal.z <0:
                direction = -1

        second_face_normal=direction*edge_vector.cross(polygons_next_to_edge[0].normal)

    (a,b,c)=change_vector_basis_from_orthogonal(edge_vector,polygons_next_to_edge[0].normal,second_face_normal,point)
    return (edge_vector,polygons_next_to_edge[0].normal,second_face_normal,a,b,c)

def try_to_move_relative_to_edge(point,ob,ig_edges,multiplier,ig_polygons):
    adequete_edge_and_distance=()
    for edge in ig_edges:#lets go through edges and find the one that is closest to the point
        (edge_vector,normal1,normal2,a,b,c)=calculate_root_vectors_and_transform_vertex(point.co-ob.data.vertices[edge.vertices[0]].co,edge,ob,ig_polygons)
        #print (edge_vector,normal1,normal2,a,b,c)
        distance=(b*normal1+c*normal2).length

        if (len(adequete_edge_and_distance)==0 or distance<adequete_edge_and_distance[1])and 0<=a<=1 and 0<=b and 0<=c:
            adequete_edge_and_distance=(edge,distance)

    if not len(adequete_edge_and_distance)==0:
        adequete_edge=adequete_edge_and_distance[0]
        (edge_vector,normal1,normal2,a,b,c)=calculate_root_vectors_and_transform_vertex(point.co-ob.data.vertices[adequete_edge_and_distance[0].vertices[0]].co,adequete_edge,ob,ig_polygons)

        point.co=a*edge_vector+multiplier*b*normal1+multiplier*c*normal2+ob.data.vertices[adequete_edge.vertices[0]].co
        return True
    return False

ob = bpy.context.object
multiplier = 2
print ("start")

ogi = ob.vertex_groups["OuterGroup"].index # get group index
igi= ob.vertex_groups["InnerGroupTriangle"].index
ig_edges=[x for x in ob.data.edges if is_edge_in_group(x,ob,igi)]
ig_polygons=[x for x in ob.data.polygons if check_if_face_in_vertex_group([ob.data.vertices[i] for i in x.vertices],igi)]
ig_vertices=[x for x in ob.data.vertices if is_vertex_in_group(x,igi)]
i=0
to_go_trough=len(ob.data.vertices)
for v in ob.data.vertices:
    i+=1
    print(i,"/",to_go_trough)
    #input("Press Enter to continue...")
    if is_vertex_in_group(v,ogi):#go through only vertices that are in outer group

        projection_was_made=False
        adequate_polygon_and_distance=()

        #print("############# vertex:",v,v.co,"*************")
        for polygon in ig_polygons:
            verts_in_face = polygon.vertices[:]
            #print(verts_in_face," checking")

            #print(verts_in_face,"in inner group")
            (a,b,c)=change_vector_basis_from_orthogonal(ob.data.vertices[verts_in_face[1]].co-ob.data.vertices[verts_in_face[0]].co  ,ob.data.vertices[verts_in_face[2]].co-ob.data.vertices[verts_in_face[0]].co,polygon.normal,    v.co-ob.data.vertices[verts_in_face[0]].co)
            #print("a:",a,"b:",b,"c:",c)

            if 0<=a and 0<=b and a+b<=1 and 0<=c:
                #print("abc in range")
                if len(adequate_polygon_and_distance)==0 or c < adequate_polygon_and_distance[1]:
                    #print("cccccccccccccc",c)
                    adequate_polygon_and_distance=(polygon,c)

        if len(adequate_polygon_and_distance)>0:
            #print(adequate_polygon_and_distance[0].vertices[:],"//////////////////////////////////")

            verts_in_face = adequate_polygon_and_distance[0].vertices[:]
            (a,b,c)=change_vector_basis_from_orthogonal(ob.data.vertices[verts_in_face[1]].co-ob.data.vertices[verts_in_face[0]].co  ,ob.data.vertices[verts_in_face[2]].co-ob.data.vertices[verts_in_face[0]].co,adequate_polygon_and_distance[0].normal,    v.co-ob.data.vertices[verts_in_face[0]].co)
            #print(a,b,c)
            v.co=a*(ob.data.vertices[verts_in_face[1]].co-ob.data.vertices[verts_in_face[0]].co)+b*(ob.data.vertices[verts_in_face[2]].co-ob.data.vertices[verts_in_face[0]].co)+multiplier*c*adequate_polygon_and_distance[0].normal+ob.data.vertices[verts_in_face[0]].co
            print("polygon")
            projection_was_made=True

        if not projection_was_made:#vertex v wasn't above a face in inner group
            #print("edges")
            if try_to_move_relative_to_edge(v,ob,ig_edges,multiplier,ig_polygons):
                print("edge")
                projection_was_made=True

        if  not projection_was_made:#vertex v wasn't above an edge in inner group
            print("vertex")
            point=v
            vertex_and_distance=()
            for inner_vertex in ig_vertices:
                if (len(vertex_and_distance)==0 or vertex_and_distance[1]>(inner_vertex.co-point.co).length):
                    #print("sdfsdf")
                    vertex_and_distance=(inner_vertex,(inner_vertex.co-point.co).length)

            point.co=vertex_and_distance[0].co+multiplier*(point.co-vertex_and_distance[0].co)
    #bpy.context.scene.objects.active = bpy.context.scene.objects.active

Do you run this once, or drag a slider in the redo panel to adjust the thickness? Anyway: there are a lot of loops, and you should optimize them away as much as possible. For group checks, it's wise to build an own lookup dictionary. There are probably more algorithmic improvements like this (pre-compute something that helps to avoid costly operations). RNA access can be slow too. Aliasing may help, or auxiliary data structures stored using primitive Python data types such as dicts, lists...

Is that printing a lot? Print usually is one of the slowest operations in scripting. Other than that I'd look into custom data arrays. You can try to find the bottlenecks with time.time() checks.

Just to echo kheetor,  print slows down everything, even worse when its happening in a loop.

You may want to look up the else clause of a for statement. It won't solve the problem, but will make your code simpler.

The code has many loops and python calls. In general when optimizing you can look for a better approach in achieving your goal making less clock-cycles and making it therefore faster.
Looking at the script I would first think of a datastructure that will allow you quick lookups and thereby remove the for loops.
This can be done by using python's dict. You can create a dict with keys being faces and their values a list of the vertices. A lookup in a dict is much cheaper than a lookup in a list.
Also the order of execution can help.
First find all vertice_indexes and that belong to the InnerGroupTriangle group. It will be easier to use the in statement in stead of the loop you have now.
def is_vertex_in_group(vertex,group):
    """ Use the group object in stead of the group_id """
    return group in vertex.groups

vertex_indexes_in_group = set([i for i, x in ob.data.vertices.items() if is_vertex_in_group(x, ig)])

Finding edges will be much easier as you can just check if both vertex indexes are inside the set
return set(edge.vertices) & vertex_indexes_in_group

As you see with just some simple adjustments I removed a lot of code, complexity and increased the performance. 3D programming is really knowing what datastructure to use for the task.
After making sure your algoritm is more optimized. You can also find area's that need attention by profiling. See https://docs.python.org/3/library/profile.html it will give you a report what part of your code takes most time and most number of calls.

My first script had two nested loops, which resulted in many "saved" steps which can be undone by Ctrl-Z. Using the default value for steps save resulted in the script taking days to complete.  Resetting the allowable saved steps to 5 lets the script run in a few hours.
How increase/decrease undo steps?

This seems like a "kludge" rather than a solution. There must be some way to avoid this problem, as there are far more complicated addons that don't have this problem. I suspect there's a way to either 1) tell Blender "none of these are 'undoable' steps," 2) prepare all the data ahead of time and execute in one step, or 3) use functions/methods that don't generate 'undo' steps.


text:
How do I activate the editing box at bottom of "Tools" section?
When I add a new item (sphere, cube etc) the lower left hand editing box is no longer activated....it is clouded over and unresponsive. For example: I add a UV Sphere but can no longer change the segments, rings, size etc. It was working in the past which makes me wonder if I have inadvertently turned it off....I have closed and reopened Blender but cannot rectify this issue.

There should be a litte + sign at the bottom, try to click on it and drag it upwards.

Related answer: http://blender.stackexchange.com/questions/23037/cant-find-the-palette-to-alter-new-objects

I tried the "+" sign but it just opened a new window.

in 3D view, use T to make the toolshlef appear/disapear.

You can also use F6 to get the specific toolbox for new objects

T key is fine but the area at the bottom is greyed out and unresponsive....I have MacBook Air and have activated the top number row but F6 does not work.....any other ways?

you'd better try to load factory settings from file menu, you probably did something wrong.

Got the F6 working but the box that appears is cloudy grey and unresponsive....I can read all the stuff in it as the illustrated box above but it is cloudy and dead.....

Thanks for the help....I will re load the factory settings as suggested..

be careful when you install addons or change settings, always check if the problem comes back


text:
My Model disappears into the Blender Universe
I was naming bones while rigging my model. While typing a bone name I saw my model move upwards without my knowing command. I eventually found it from a speck in the far distance. I scrolled it in successfully. But now it fails to respond to "View" commands. If I hit "7" for aerial view it disappears....again I find it as a speck and scroll it in. This happens with all "view" commands...
When I do locate it and try to drag it around it is as if there is a pivot point miles away and the slightest grab and drag sends it into oblivion.
My pivot point is set on default and my manipulator is set to Global. My model stays in the correct position on the grid all the time.
Any suggestions would be greatly appreciated.

try to select your model and press the period key on your numpad

I'm on a laptop but the period key did seem to work. Thanks for the help.

Could you mark it as the best answer if it was helpful


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Old Project reappears when rendering
I just downloaded 2.76 and successfully rendered a project yesterday. But today with a different project the Render fails to work correctly. The old (yesterday) project reappears and begins to render.
Wonder if it is a bug?
Thanks!

Did you save over the startup file??

Just checked and yes I do. The problem is fixed. Many thanks @cegaton.


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Image textures with transparancy Help
How can I mask an image?
I imported a downloaded image from CG textures that had the chequered background.
I converted it from JPEG to PNG.
I imported it into Blender 2.74 and later in 2.76 as an "Images as Planes"
Adjusted the "Import Options" to "Use Alpha" and " "Premultiplied" and "Emission/Transparent" but it still shows the chequered background when rendered.
I also did the long way with UV unwrap and "Transparent" nodes and Alpha noodle In Image texture to Mix shader "Fac"

Does this help: http://blender.stackexchange.com/a/27635/3710 ?

In Blender transparent areas are not rendered as checkers... if you converted a jpeg that had checkered background to png, that does not make checkered areas transparent!! Your png has no transparency, I feel, this is why the checkers are always there...
You should either download that image again, but directly in a format that supports transparency (like png) or convert the checkered part of the png to a true transparent area...
In Blender if an image has supposedly transparent areas completely black or white, you can tell it to use those absolute colors to get transparency  (that is the purpose of "calculate" and "invert" options in the image texture  "image sampling" panel). "calculate" uses blacks in image to represent transparency, "invert" makes "calculate" use whites.
This assumes your material and texture are set to be transparent, and the texture has some influence (>0) on material transparency.

you're welcome, we are all here on earth to learn from each others :) it was just a basic eplanation, though. the blender manual can show and explain better each texture and material option. it's though to learn all that options, and some "convention" like this alpha thing.


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How to correct the size of Properties panel in Default window?
The Properties panel on RHS of default 3D window which is activated with (N) became very small and hard to read. All other active Blender files are fine....but cannot restore/resize to normal settings and too small to read.

normally you can zoom in/out in it like in the 3D view (mouse wheel or numpad+/-). That does not work for you ?

try ctrl + middle mouse button (not rotating wheel, only click) and drag mouse up/down

Scroll wheel works in 3D window but only moves the Properties panel up or down.....numPad is the same!

and you have the mouse cursor on this panel when you do it ? You can try "home" also to restore to the default size

Control+ middle mouse corrected the problem Thanks Shubol3D    and also Lemon for efforts!


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Anim Player Error
My question is:
I have a Error: Anim PLayer
That happens if i play my scene (ALT+A) (New Scene too)
In Cycles and Blender Game i have the same Error.
For the Render i use the Render Presets
I get this error...
I have tried other versions of Blender but all Versions same problem.
Good to know:
Blender Version: 2.75
Windows-7 64 Bit
AMD Six Core
AMD Radeon HD 7770
Thanks for every Answer :-)
Andre

What exactly is the error? Could you upload a screenshot or copy/paste the error message?

It isn't an error. It shows it is playing. If you push the button it stops the animation.

hmm but why did Blender thinks i'm blind and dont see the timeline.....

The
button means animation player has been turned on (ALt + A is shortcut, press again to turn off).
You can see whether animation is playing looking at the frame numbers in the bottom left of the 3D View:

Note numbers in the bottom left change and sometimes become orange - that's the keyframe of the selected object is on adjacent frame.
The simplest way to see the timeline is to switch screen layout from Default  to Animation, the timeline will be in the bottom.


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How to make use of a cubemap in Blender Cycles
I have a cubemap I got from somewhere that I want to use as a skybox for a scene, but it seems that there are no options in the World context to set it as the texture surrounding everything. "Image Texture" for Background color only gives me a single color across the scene that (I'm guessing) is the average of the colors in the texture, and "Environment Texture" doesn't allow for cube-based projection. How would I go about utilizing the texture I've gotten?

You could just UV unwrap a Cube object, map the texture to the inside faces and then scale it up large enough to contain your scene. Should work just fine.


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geometry nodes advect points using vdb or embergen particle velocity
I've run into a problem when trying create curves that follow a simulation from embergen. I've tried a few routes but they all seem to be dead ends
Option 1
trace then create curves from points of embergen particle simulation

roadblock - embergen particles are not exported with consistent ID's so curves cannot be created

Option 2
use the embergen vdb with .velocities attribute to advect geo-node created points

roadblock - there currently is no way to sample volume information in geometry nodes, there was an experimental build but I can not find where to find the actual build https://projects.blender.org/blender/blender/pulls/107656

Option 3
somehow use the velocity attribute that does come with embergen alembic particle export and advect the geo-node created points using this

roadblock - this may be a limitation of my geonodes knowledge, but I am unable to transfer attributes from the embergen particle points to geonode created points

Did you tried to enable experimental volumes option in the settings of the daily build?

Hey @modnop how would I go about doing that? I had a look at the daily build but couldn't find any experimental volumes options


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Blender 2.8: How to render viewport animation by taking viewport antialiasing settings into account?
Do someone know how to render a viewport animation by taking the viewport antaliasing settings into account?

Thank you
Chris


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Compositing: Ho to scale compositing results to different image sizes?
I have a compositing and would like to save the image result to individual files by using different image sizes.
Currently I only know the end size of an composting result is based in the scene render size.
But is there a way to scale the image and save it with the new size?
This would safe me time.
Thanx


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How to use a material node data path as driver, that is located inside a material group?
I would like to get the data path of a material node, that is located inside a material node group.
I would like to use it as a driver. In Blender 2.8 you can just copy a data path to use it for drivers e.g.
But if you do this for data inside a group, then it will be refreshed only at rendering time or if you play the animation, but not in realtime.
How to get the complete data value path for nodes inside of material groups?
How the complete data path have to be written?
node_tree.nodes["Group"]. what have to follow then to access a math node e.g.?

With blender 2.81 and up you can right-click in the field and choose "Copy as New Driver", then right click in the driven field and click "Paste Driver".

The resulting data path (in my file anyway) :


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Is there a way to edit unassigned materials in the shader editor?
I have a material, that is not assigned to any object. I use it as a material override in a pass (View Layer) only.
Do someone knows a way to edit (see) materials in the shader editor, that are not assigned to any object?
Thank you

You mean not assigned but linked or neither assigned nor linked? Having material linked but not assigned is a way to go with overrides.

Hello :). There's no way to edit unassigned material. Why not just add a new object to use for preview, and disable it in render and viewport?

The workarond, that I've finally used is to create a dummy object, which is always invisible (even in render) and use it as a material container. I hope there will be a better solution in the future. Thank you!


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How to get "object texture coordinates" in geometry nodes?
Do someone knows how to use object texture coordinates in geometry nodes, like we can do it in the shader editor for materials?
I would like to keep the sampled texture size proportions for the distribution always the same on all objects. Currently the size will be shrinked on non quadratic objects, when I use the UVMap atrribute.

I've figured it out. Here's the solution, for everyone interested.

Just beat me to it :)  BTW, Blender Guru, in his tutorial, wrongly identifies position with the 'Generated' output of the Texture Coordinate node. It's the position, in Object Space, so equivalent to the 'Object' output.


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Add baked texture to render (Cycles)
Hi I'm having a problem with baking textures. I have done one but I don't know how to add this texture to an object to speed up rendering. The texture is visible in Viewport Shading: Texture. But rendering is as slow as before. Is it possible to turn off shadows and other things for only this object with baked texture?

Could you post a .blend file.

What you wan't to do is use an emission shade-less material:
In the material node editor, use a setup like this (The UV map is optional) It is important to keep the strength of the emission node down to 1

If everything in your scene is baked, use this to cut render times:
You can also avoid a-lot of extra calculations by cutting down on the samples and light bounces. You can set all of these values to 1:

You need to select the baked texture in the image texture node.

Once you have the texture baked you need to assign it as an emission material to the object.
This is pretty simple:

Go to the node editor
Disconnect any nodes you have plugged into the surface socket on the material output node (you needn't delete them).
Add an emission shader and an image texture node.
Select the baked texture on the image texture node and plug it into the color input of the emission shader and plug the emission shader into the surface output.  Make sure the strength of the emission shader is 1.00.

Note that if the camera is animated, baked glossy sharers will not look right.
For further reference, see Andrew Price's Introduction to Baking in Cycles.


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Cut big mesh (plane) in quadratic parts
I am working on a game-engine and the time has come to model a simple map. I thought, since i already use blender for models, why not for the map, since creating a world-editor can be time-consuming. The problem is, my engine expects the world to be in quadratic chunks of equal size. I'd like to model the map as a big plane with structures on-top in Blender and afterwards, cut the whole scene with plane and structures in equal quads to export them individually. Is this possible?
Example:

I'd need the whole terrain-plane to get split at the red lines and the little house, so every part of the house is in the corresponding chunk when i export the chunks.
Alternatively, when i create multiple equal-sized quadratic planes, to somehow glue one edge of one plane to another edge of another plane, so i neither get holes in between, nor get overlapping faces?

for a few cuts you could try the knife tool, a simple grid as reference, straight cuts

You can try to use some kind of wireframe (plane with deleted face and enlargened by Array) and cut your original plane with Knife Project (first plane as cutter)

To do this first join all your objects into one if they aren't already by selecting them all and hitting Ctrl+J.  Then create another grid object consisting of just edges which you will use to slice up the map.

Select the grid and then the terrain (in that order), enter edit mode, go to top view (numpad 7), make sure you are in orthographic mode (numpad 5 to toggle), then use the knife project tool found in the toolbar.  Make sure cut through is checked after you do so.

Your terrain will then be sliced up based on the grid object's edges.

Thanks, this helps a lot, however, if i merge all meshes to one big mesh, wouldn't this mess up my UV-coordinates? Now that i think about this, it's really bad to build the objects into the map directly... I think it'll be better if i build only the terrain in blender and then use some other technique to place objects like houses and trees.

@tkausl  No, it shouldn't mess with the UVs.  You can separate them when you are done if you need to using [P] > loose parts.

Oh thats good. I'll see how this works, thanks.


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Collada export breaks bones
I am trying to export a Model with a armature as .dae file to load it with Assimp into my game engine. The problem now is, Blender breaks the bones.
This is how it looks when I am exporting.

When I then start Blender again and try to import the dae again, I get this:

In my game engine, which renders other animated.dae files perfectly fine, it looks like this:

I am not sure where the issue is but I guess it's me being too dumb to use Blender correctly.

After googeling hours and hours i found out, Blenders Collada exporter is just buggy. For everyone who wants to use Blender and Assimp together i recommend the FBX file format. Both, Blender and Assimp do support it, you can configure Blenders FBX exporter to use the correct Coordinate-System (-z forwards, y upwards) and it even supports exporting all animations on the animation-stack as individual animations.

Thank you very much for the suggestion. FBX works fine for me as well. The problem with Collada is that it duplicates some bones without any reason. Names are also the same, so the matrices are all mixed up

I have found this add-on which fixes most Collada issues with Blender
https://github.com/godotengine/collada-exporter

This works for Xcode using SceneKit with Swift. If you use a texture, you need to change the Emission from White to Black.


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Applying a texture to a cube shows up in the editor under the texture viewport and doesn't in render
I have applied a texture to a cube in Blender 2.69 (unable to upgrade at this time) following this guide https://www.youtube.com/watch?v=il7ajiCepus. It shows up in texture view, as well as solid, but it will not show up in render. Any ideas?

Yes. I followed the tutorial I linked to exactly, I think.

yeah, whenever there is something you don't think would be reasonable for us to say "Oh yeah! Here's is your problem and here's how you fix it!" or there is something that could be caused by several factors, it's helpful to upload a .blend file. Thanks!

http://www.pasteall.org/blend/33280 is the .blend file.

So i had a look , but no textures were in the file so i took a guess , What i THINK is wrong is that you have assigned the material with no texture , To fix this , in the image below there are 2 materials , click the negative button ( make sure you have selected the material with no texture ) . Then go into edit mode , and press a until everything is selected , Click the logo material and click assign

THANK YOU THANK YOU THANK YOU SO MUCH! It works perfectly now! Thank you!

:D Yay , No problem bro !


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In viewport, mesh is see-through, objects behind it are displayed on top
Many years of blender experience and just encountered this infuriating little problem:
I have a red ball mesh, a green rod mesh.
No matter how they are positioned, the viewport displays the red ball mesh BEHIND  the green mesh. SMDH

How do I correct this so that objects are displayed normally?

Make sure you didn't activate X-ray for the green mesh.

Make sure that the display properties of the object that is appearing on top of other objects is not X-Ray


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CPU and OpenCL gives 2 different rendering result?

the 1st pic is made by cpu, the 2nd opencl. How do I make OPENCL work the same as CPU?

It depends on some things, particulalry the fact whether all the shaders / features you used are actually supported with OpenCL like SSS or HDRi map etc. Somewhat related - http://blender.stackexchange.com/questions/40341/cycles-render-is-different-when-rendering-with-gpu

Yes, OpenCL is pretty much experimental at this stage, not all features are supported yet. Some shaders don't work, it looks like you may be using translucency or sub surface scattering which may not be supported under OpenCL.


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Blender 2.77 glitching whenever it processes
Please help this rookie! .I just installed blender v2.77 and it significantly faster than the previous one when i'm working on the same file. However blender glitches everytime it calculating something, and everything is fine when everything is settled, and the glitch is quite annoying as seen bellow, how do I fix this:

Thanks a lot!

you should test you VRAM. You'll find infos and tools here and here

Hi, thanks for the suggestions, when I turned off services and startups everything work fine except that blender got slow again like usual, this glitch is actually a consequence of an improvement (hopefully)! still have no explaination of the cause though, but wouldnt mind a bit of visual annoyance for a lot of speed =)))


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what is the point of having the same object in multiple layers?
What is the point of having the same object on multiple layers when the change you make on the object affects all layers selected? In other words, on what occasion can I use this feature effectively?

Do you ask about render layers or 3D layers ?

@mrZak I think its about 3D layers

Camera:
If you have the camera in multiple layers, you can always see where it is positioned.
Lighting:
If you have lights in multiple layers, you can see all your objects under the same conditions.
Meshes:
If you have meshes in multiple layers, you might not have weird shadows caused by an object that isn't visible.
These are only a few; render layers are a very powerful tool and have many functionalities.

If you key two particle streams to create a new object you can key to the second image on the second layer. In this his example, both streams flow in one layer, but one is actually pointing to the imagine on another layer.


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Why is my solid and wireframe behave like this?
My solid and wireframe has been behaving like this while my eevee and cycles still function normally. Here I can only see what is inside that weird light gray thing, while my eevee viewport function normally.

You have pressed Alt+B. "Clipped" in the title of the viewport indicates this:

Press Alt+B again to remove clipping
More info about viewport clipping


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Render Object with CT scan effect?
Is there any addons or tricks that I can use to turn my object into a CT Scan result? meaning they looks like this from all angles:

Greatly appreciate your help!

Related: How can I make texture and material look like an MRI?

Volumetrics
X-ray images can be simulated with the use of a quite simple volumetric shader in conjuction with a very good modeling.
The information stored in such imagesis basically just one: how fare the X ray radiation goes far? The variations is caused by the different nature of materials. Each one of them let the ray pass more or less.
In Cycles engine, there is no X-ray radiations, but we can simulate the behaviour with light. The energy of the source will be absorption by passing through a volumetric shader like the following.

The hard part is that you must:

model everything with it's own, real, thickness in order to achieve a correct absorption calculation

create a different volumetric shader for each kind of material of your scene (one for glass, one for metal, one for filament...) and estimate the light absorption value (driven by the Density parameter).
The model in the above picture comes from a collection of CC0 Bulbs on Blendwap


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how to manage big project?
I'm working on a room with lots of stuff. This project worries me as I look at the outliner's growth. I know in term of management blender's outliner is already pretty amazing but can you suggest any better way to reduce confusion?
for example when I make an indoor plant with a lot of leaves I'm gonna have leaf1, leaf2, leaf3 ...etc How do I get all the leaf into 1 one folder?
thanks a lot

related: http://blender.stackexchange.com/questions/36533/how-to-easily-organise-your-blender-scene

Presumably the leaves will be part of a plant - in which case you'll want to set them to be Children of the parent plant. This way when you manipulate the Parent (eg, move, rotate, scale) the children will be similarly affected rather than being left behind. You can easily Parent objects by selecting all the children, holding Shift and selecting the Parent (so the parent is the last object selected) and then pressing Ctrl+P and select from the Parent menu. When you do this the outliner will show them as being within the parent object which can be collapsed to hide them (ie, the Parent effectively acts as a folder for its children).


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Geometry Nodes: How to simulate rotation achieved with "Distribute points on Face" when using a "resample Curve" of edges extracted from a mesh?
I'm trying to achieve the effect of the below nodes setup combined togheter, distribution of points taken from "resample curve" node and the rotation taken from "distribute points on Faces" node.
Correct distribution but wrong rotation of instances:

Correct rotation but wrong distribution of Instances:

The problem is that i cannot use points from curve and plug in the rotation from Distribute Points on Faces node.
Is there a way to achieve what i want?

Would you mind showing the base geometry you get from the input? Or maybe upload a file? Because maybe there is something different in your file which is not visible in the screenshots so that the answer proposed by Crantisz does not work.

Well, you can grab a normal from the nearest surface point from the mesh and convert it to rotation using align Euler to Vector node:

Two Align to Vector nodes makes it aligned horizontally also:

Unfortunately this doesn't seems to work for my case. this is the result https://imgur.com/7cZU3eG

Take a look at this tutorial, see if that helps: https://www.youtube.com/watch?v=IQdT5kACMQc


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tread tire in snow + animation
I would like animate and render a car driving in a snow, so my main issue for the moment is to have the tread of the tire (and sometime a rough mark) during the car is driving.
See picture bellow
I was thinking do two planes, one with the snow and the tread mapped where I want on the plane, And an other plane WITHOUT mark on the ground. And play with the opacity of the two plane in After Effect or in blender with mask . But I have no idea how to unwrapped the tread mark exactly where I want, AND I have to calculate my scene twice...
Any other ideas are welcome :)
Render engine : Cycle

Thank you ! I never really use this tool but it seems to do what I want !


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Topology modeling
I can see, many different way to modeling, as long as there 4 edges, but in this case is it just my way to tweak the vertices which is not good or just this kind of topology which is not adapted to this corner ?

you could try looking here: http://polycount.com/discussion/56014/faq-how-u-model-dem-shapes-subd-mini-tuts-aka-use-the-right-amount-of-geo for some inspiration :)

It's kind of hard to understand your question, but your pictures give me a good idea. Looks like the curved corner is deforming. If you want to simplify your mesh, you can try the following.

Select the vertices marked in red, Alt+M > Merge at Center
Select the vertices marked in blue, Alt+M > Merge at Center


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Thickness map grid type
I'm wondering how I could had a thickness to this pattern made with a map (1) ?

I don't want to model it because the idea, is to change very often new sort of pattern to have a quick review of what it looks like in an object, there is a lots of pattern, the proportion are constently changing, so an other team do it in illustrator.
I tried solidify modifier but part are missing (2)

I tried the displacement map (nodal), but it is not strong enough
I tried the displacement modifier but it is way too much heavy and the result is not sharpe at all
and now I'm running out of solution, any Idea o help ?

Yeah you can't really just add thickness to an image texture just like that, if you could no one would really ever bother modelling, they'd just make textures. If it was done in illustrator try importing it as an SVG curve and then extrude it.

Also you could take the image to the compositor first and add some Dilate/Erode node to it, then save and use.

I don't know how to interpret the question. Do you want to make each "Y" shape looking 3D or do you want white parts to be higher than black ones? Also, could you provide a blend file with the overall shape and the map?


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Blender character rigging with cloth wrapped over the body
I've a character that's draped with a piece of cloth along it's waist and it runs down along the leg as well. That is, the legs of the character are loosely (not tight fitting) , but entirely covered by some garment. I have fit a rig to the character and did the skinning by parenting the character to the armature. So now when I move the armature the corresponding limbs of the character also moves , as expected (in Pose mode). But the legs of the character penetrate through the cloth when the legs are moved.
I want the rigging such that the cloth is also part of the system. When the legs are moved, they should push the covering garment, and not penetrate through it, or tear it. The character has a Collision modifier already added to it, and the garment has a cloth modifier. How do I do the rigging with the character's clothes on?

put the cloth modifier under the armature modifier, setup your keyframes on the rig and simulate the cloth.

There is a function to copy vertex groups to non-matching meshes. It is great for automatically skinning clothing on characters.
First select the character mesh, then shift + select the clothing. Press spacebar and type "transfer weights". An operator should show up. This seems to be broken in the latest blender 2.74+ but try 2.73. (I just tried on a copy of 2.71 I have laying around and it works well).
The new versions have "Transfer mesh data" but it does not seem to work for me.
Cheers!

I did the weight transfer thing, but additionally what was required was to parent the cloth as well to the armature. Do add that to your answer..Thanks!

I will add that I figured out how to use this function in newer blender versions. Select the source mesh. Select the destination mesh. Go into weight paint mode, and on the left side "drawer" there is a transfer weights function. Seemed to work after mucking around with it for awhile.

The "transfer weights" totally workes..
it is in the newer versions also but in a different place..

1- Parent the cloth to the armature
2- Select the Character mesh then Shift+ select the cloth
3-do as in picture.. (from "Weight Paint" ,, select "Weights" in the 3D view header.. then Select"Transfer Weights")
That should do it.....

Parent the cloth to the armature with which option? I tried with Armature Deform with Empty Groups, but nothing works :( Using 2.78

followed all the instructions and now it seems to only be following one bone which is the one i think i parented to while the armature was in object mode. Regardless this did not work

I tried 2.76 and never worked. I sent a bug report and nothing. It was closed as invalid. Ha. So I uninstalled 2.76 and got 2.73 from http://archive.blender.org/download/get-blender/older-versions/index.html. It worked right away following tutorial https://www.youtube.com/watch?v=WVfTRwXpmuQ. Went back into Pose mode and cloth moved with rig. The robe needed some adjustment, but it worked!!


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Query grease pencil strokes from python
I want to "query" grease pencil data from my python script. In some sense, I need to get the points of the sketch and their coordinates to do some curve fitting. Is there a way to do this via python? Also, is there a higher level API that can give me more information about the strokes drawn?

Grease Pencil data is stored globally in bpy.data.grease_pencil. Scenes and objects can reference a Grease Pencil datablock.
Up to Blender 2.72, the active object was used. With no active object (right after object deletion), the active scene was used instead. From 2.73 on, the active scene is chosen all the time. There's legacy support for the object level however. For future use, you should assume the GPencil data to be associated with the active scene:
gp = bpy.context.scene.grease_pencil

The GPencil data is hierarchically organized in layers, frames, strokes and points:
# Get 1st point of 1st stroke on active frame and layer
point = gp.layers.active.active_frame.strokes[0].points[0]

point.co       # 3D Vector location
point.pressure # tablet pressure (1.0 on mouse input)
point.select   # selection state (bool)

layer = gp.layers[0] # first layer (by index)
layer = gp.layers["GP_Layer"] # by name
layer.color # color (fill_color for fill color)
layer.alpha # opacity (fill_alpha for fill opacity)

frame = layer.frames[1] # 2nd frame
frame.frame_number # frame number of that frame object

stroke = frame.strokes[-1] # last stroke
stroke.draw_mode # e.g. '3DSPACE'

You can create new GPencil data from scratch too:
gp = bpy.data.grease_pencil.new("My GPencil")
scene = bpy.context.scene
scene.grease_pencil = gp
scene.frame_set(5) # ensure we'll see the stroke (set to frame 5 below)

layer = gp.layers.new("Name for new layer", set_active=True)
layer.info # note: it's not layer.name!
layer.color = (1, 0.3, 0)

frame = layer.frames.new(5) # frame number 5
stroke = frame.strokes.new()
stroke.draw_mode = '3DSPACE' # either of ('SCREEN', '3DSPACE', '2DSPACE', '2DIMAGE')

stroke.points.add(4) # add 4 points
#stroke.points[0].co = (..., ..., ...) # set 1st point's location
stroke.points.foreach_set("co", (0,0,0,0,0,4,0,6,4,8,6,4)) # set all at once efficiently

when I create grease pencil strokes this way, they do not show up until I draw another stroke manually in the 3d view.  Is there a datablock I need to update?

I'm not sure, it could actually be a bug. I extended the script to call all possible update methods, and yet you still have to draw a stroke manually to make it visible: https://hastebin.com/ulisoyivas.py - The only thing that I see changing by that user stroke is, that it actually sets the active frame. layer.active_frame = frame set by the script is completely ignored and the value of active_frame remains None without apparent reason.

Im glad the behavior is reproducible.

Retried with Blender 2.79 (5bd8ac9) and it works without problems, even without all the update calls, frame.frame_number = 1 and even layer.active_frame = frame. The stroke appears immediately in the viewport. Which version did you try?

2.78b and c....forgot about 2.79 :)  will try asap when I get home

Eventhough this one is already answered with Python Script solution, I just wanted to add this Sverchok Node Tree solution, just to help beginner programmer in the future, just in case they are asking the same question and would like to see visually as nodes.
You can setup something like below to observe data blocks and pass on the values for other things.
In case of Grease Pencil Strokes, we can get the Coordinate and Pressure pretty easily by chaining nodes and the result if we generate Curves Output is like this:

And if we are instancing boxes along the Grease Pencil while using the Stroke Pressure and Coordinates, we get this:


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Apply texture to plane via script
What is the simplest way to apply an image texture to a plane using python (in 2.73)?
I've tried the script give here, where I replaced the cube with a plane:
http://wiki.blender.org/index.php/Dev:2.5/Py/Scripts/Cookbook/Code_snippets/Materials_and_textures#Textures
But, it didn't work. Perhaps there's a different method for 2.73?

The texture script there still works in 2.73, but there are a couple points that you may need to check.

Render engine needs to be set to Blender Render, the sample script is not setup to work with cycles.
The viewport shading settings. The texture will not show if the viewport is displayed in solid shading. In Textured shading you also need to enable GLSL instead of the default Multitexture. In Material shading the texture will show. These options will only show the image part of the texture, you will only see the full result of the texture in rendered display of the viewport or if you render an image (F12).

The Viewport shading mode can be found in the header of the 3dview -

GLSL shading can be enabled in the Shading panel of the properties sidebar (press N) -

If you want to adjust the script to work with cycles this question might get you started.

@sanjeevmk if this answers your question mark it as accepted , if not edit your question to clarify what you're looking for


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Get updated mesh data after editing
I converted a curve to a mesh, and got the mesh data with:
   mesh = bpy.context.object.data

This mesh had 47 vertices at this point. Then , I extruded the mesh (via script) along Z, and got 47 new vertices because of that (total 94)
However, this new addition is not reflected in my mesh data now. If I now perform some new operations using mesh.vertices , it only affects the older vertices and doesn't affect the new ones.
How should I go about this?

I did a quick test and it looks like you have to leave edit mode to get updated object data.


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Cloth Simulation : Self collision results in cloth "exploding"
I'm trying to model a cotton garment by simulating it's draping process. I'm having issues only when I enable self-collision of the cloth. Without self-collision , there are no issues but I do need self-collision for later stages of work and can't proceed without enabling that. I'm using 2.73, and I didn't modify any settings; that is , I use the default collision settings and for everything else too. Below are screenshots of the issue.
Rest state:

End result, without collision, close to what I want; but as seen, cloth is penetrating itself:

When I enable self-collision, this happens right from the 1st frame itself:

The end result is also similarly messed up.
These are my cloth settings:

I believe that the simulation is finding the cloth particles close together and hence repelling them from each other, given the messed up result. I set the "distance" value in the collision settings to 0.5 and 1 too, but both of them gave the same result.. Any idea why this could be happening?

In your screenshot Blender states, that the cache is outdated. The first thing i'd try is to clear the cache (e.g. set frame to 1).

Yes, I tried 0.5 as well..same thing..

@PiotrJędrzejko Didn't get you exactly...rotate and scale what?

@sanjeevmk See this post on applying transforms.

I'm not sure how the setting relates to measurement, but I believe your self-collision distance is way too large. I believe the numbers relate to 'real-world' or blender units, so you need to make sure if you have a dense mesh, that the self-collsion distance is smaller than the closest vertices you want in the simulation. Often I'll set this somewhere around .05 or even much smaller e.g. .001. The cloth engine has also changed a fair bit since this question, but maybe this will shed some light for someone.
EDIT: yes it seems the newer cloth refactor by Luca Rood calculates collisions in real units, therefore the distances need to be pretty small.

A POSSIBLE WORK AROUND (that at least worked for me):
Scale up everything, then apply the transformation (CTRL+A > all transforms)
Sometimes cloth simulations in Blender results in error with too small meshes.
Hope this may help.
G


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Dynamically pin cloth when animating
The way it works now is, I assign some initial pinned vertices to the cloth and model the simulation. However, I'd like to unpin some vertices and pin some new vertices in between the simulation. I want the pinned vertices to switch in between.
I'm doing all of this via scripts (not blender UI).
Is something like this possible?

Tried dynamically switching pinned vert groups - that resets simulation.
Tried dynamically changing vertex weights inside group - that resets simulation too.
And the bake wouldn't work at all, that was clear from beginning.
The workflow I suggest is to

simulate part of your cloth animation with one set of pinned verts and then save the animation as .mdd mesh cache.
Then apply the cloth modifier, add another and simulate with different set of pinned verts. Export to .mdd
After you have all the parts, load them to Mesh Cache modifiers and blend them with influence. With good blending you can mask some of the discontinuities that happened while switching simulations.

Since any motion between simulations will be canceled you would need to adjust with force fields and plan the transitions carefully. But that's probably the best you can do.


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Create a configuration window for my add on
I'm making an add-on that is supposed to take in a lot of user-decided configurations . I know I can create panels and stuff, but I'd prefer to create a configuration window that pops up and fills the entire screen, since there are too many options to select, and I also have to show some image thumbnails.
This new window can have all my configuration options laid out in any way I want, and can take any size, and has a close button. It can be opened using some hotkey or button when the user wants to use my add on.
Is something like this possible?

You could possibly create a separate program and run that from the blender add-on (os.system("some_executable.exe"). That program could have whatever interface you like (recommend PyQt for cross-platformness), and simply save the user's choices to a text file that the add-on then reads. But if most of the user's time is spent in blender using your tool, it'd be best if the entire interface is consistent and within blender.

Add-ons can have their own user preferences.
https://docs.blender.org/api/current/bpy.types.AddonPreferences.html
This doesn't fill the entire window, but this is the intended way for your add-on to be configured.

The design you propose is not very blender-like. The way this should be are options under the addon box in User Preferences > Addons. This is how you implement it:
import bpy

class SomeAddonPrefs(bpy.types.AddonPreferences):
    bl_idname = __name__
    # here you define the addons customizable props
    some_prop = bpy.props.FloatProperty(default=1.0)

    # here you specify how they are drawn
    def draw(self, context):
        layout = self.layout
        layout.prop(self, "some_prop")

# and this is how you access those settings in your add-on code
some_prop = bpy.context.user_preferences.addons[__name__].preferences.some_prop

#for 2.80 use
some_prop = bpy.context.preferences.addons[__name__].preferences.some_prop

# classes needs to be registered of course


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Show an image in a panel/window
A typical blender panel looks like this:

We have a layout object, and we typically add stuff to it. My add-on lets user select from many garments, and for that, I need to be able to show the garment images clearly. So I can't use a button icon, since the user won't be able to see the garment properly when it is icon-size.
So I need to show an image in the panel whose size I can set. Is there a way to add an image like that to the layout of the panel?

Yes, I know it's a duplicate. But there are no answers or recent activity on that question hence asked a new one

There is an answer..? Without an answer, it's not possible to close another question as a duplicate of it.