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Baked normals not calculating gradient smoothly when using a depth map
I'm currently trying to bake normals using a depth map generated from a rigid body simulation I did featuring a few hundred coins -

The problem I'm encountering which I wasn't able to find anywhere else (potentially because my approach is flawed) is the presence of these noisy lines that run across the gradient of coins which don't lay flat, as seen here -

Baking the depth at a much higher resolution and baking the normals again doesn't eliminate the artifacts and only makes the lines more defined with the added detail—manually painting out all of these lines is obviously not an effective solution, and I'm interested to hear if there are ways of baking the normals without the presence of the lines that very obviously catch the light when applied to a surface.
I figure that the approach of converting a depth map to a normal map in this way may be fundamentally flawed and that's why I'm potentially running into this issue, but I'd like to hear any potential solution from anyone who has more experience in the area of baking. Thanks!

How did you create the depth map?

We need to know how you made the depth map, as well as everything you ever did to it in other apps, in order to tell you what you did wrong.  Yes, if that .png is the depth map, it doesn't look great.  (Maybe it spent some time as a .jpg and suffered .jpg compression artifacts?)  The file itself would let us recreate the problem.  However, you're always going to have artifacts from bump mapping when zoomed in to the pixel level.

Save bake as OpenEXR ... You need to save in a format that supports 32 bit depth in minimum.

The depth map was generated with an orthographic mist pass over the simulated pile of coins

EXR was what did it for me (bit depth of depth map), thanks a bunch @vklidu—you can make an answer if you choose that I can mark as the solution

Great it helped :) And thank you for offer. I wanted to keep it as a comment, because it was asked many times (your Q is dupli), but I cant find now any here and you have nicely illustrated issue ... so

Your saved image doesn't have enough color informations.
Save baked pass in OpenEXR format that can save information in unclipped bit depth.


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How can I make a texture node Single User with Python the same way that is accomplished with pressing the interface button?
I have been trying to look in the API as well as Google and the search function here and haven't found an answer to how to make the actual Image Node inside the Material a Single User in Python the way we can with pressing the single user button in the interface. I already tried code the made single user of the node tree the image node is inside, but haven't found as way to mimic the button result.
I was hoping for someone to have a better idea of how to attack this - the behaviour here isn't the same as making a copy and writing to a new filepath or the like, it is storing the image in memory and ready to dump after use.

i struggled with this also! And it was a bit disappointing to me that there was not python tooltip for that button to do so! ;)

You have to find the material. In the material you have to find the image texture node.  It's not the node, but the image itself that has to be duplicated so you need to find the image and make a copy.  Finally you need to set the texture node to point to the image copy.  Here's python that will do that.

replace "'Material'" by the name of the material you care about.
the node = line in the example only handles the case of a single image node, that has the default name.
The last two lines can be combine as node.image = node.image.copy() but as written they're easier to follow.

import bpy
material = bpy.data.materials['Material']
node = material.node_tree.nodes['Image Texture']
new_image = node.image.copy()
node.image = new_image

There are several ways to obtain the material, depending on your use case.  You could, for instance want the material in the first slot of the active object: material = bpy.context.active_object.material_slots[0].material
The biggest issue is identifying which image texture hold the image and that again depends on your use case.  You might have to search through all of the image nodes in the material or you might want to use the active node.  In the later case you can use node = material.node_tree.nodes.active but you should then check that node.type == "TEX_IMAGE".
If you wanted to search all of the nodes to find images, here's a function that will do that
def find_nodes_by_type(material, node_type):
    """ Return a list of all of the nodes in the material
        that match the node type.
        Return an empty list if the material doesn't use
        nodes or doesn't have a tree.
    """
    node_list = []
    if material.use_nodes and material.node_tree:
            for n in material.node_tree.nodes:
                if n.type == node_type:
                    node_list.append(n)
    return node_list

You would call it with code like
image_nodes = find_nodes_by_type(material, "TEX_IMAGE")

and then search the resulting list for the image you're interested in, perhaps by looking for it by image name.
Note: The find_nodes_by_type function is spelled out to make it simple to understand.  A more Python-ish way of writing it would be to use a list comprehension:
def find_nodes_by_type(material, node_type):
  return  [node for node in material.node_tree.nodes if node.type == node_type]

I got a working version from that first example, but then realized I also need to make a copy of the Material first and THEN a copy of the image as you explained - thank you for the help, this is very easy to understand compared to what I had been reading.

Maybe you should also mention in your answer that you won't have to copy the image. Yes, it "looks" in the UI like it still has multiple users, but as soon as you change the image to another image you will see that it will then change to "single user". I think it is because Blender does this optimal referencing thing as programming languages do this. As long as it it the same image, Blender "reuses" the same object. If you change it, Blender "recognizes" this and then makes a true copy of the image texture node with a link to the new image. Often copying an image makes not much sense.

But good answer and explanation! +1

@CraigDJones thank you very much.  You're right.  I'd assumed that you already had a node with a multiple use image and only explained the last part.

source: Stack Exchange

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

sort: votes


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what does it mean when you HAVE to provide UV coordinates using a Texture Coordinate node (to apply materials)?
I imported a mesh from an .obj file, and I can't apply materials to it without providing UV coordinates using a Texture Coordinate node. It would just show up black when rendered.

what does this mean? Because, I've noticed when I add a Suzanne head (or any primitive mesh) and unwrap it, I don't have to add a Texture Coordinate node to apply materials to it.
thanks :]

You don't normally connect a UV socket to a Normal socket, the Normal socket is generally used for displacement or bump type of effects using either a texture or a normal map.
The fact that you connecting the UV socket to the Normal input of the material worked is probably just a coincidence, and a side effect of the fact that you mesh probably has some sort of geometrical glitch or wrong facing normals.
Try entering edit mode and clearing or recalculating your normals be selecting all faces and pressing Ctrl + N and see if that solves the problem.
Have in mind that this may destroy any custom normals your model might have (if any).

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


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Export model to unity with multiple textures
So I've searched a lot on this topic, but I simply can't seem to find a tutorial explaining how I can add multiple texture to a single model (different textures to each face of for example a cube) an export it into unity3d.
I've found outdated tutorials, where the controls has changed so you cannot do it the way they show.

All I'm trying to do, is add 3 different textures to a single cube and then import into unity3d with the textures.

Possible duplicate of Add different materials to different parts of a mesh?

As a Unity user myself i would say: avoid multiple materials on a single mesh at all times! You are adding unnecessary drawcalls! What you should look into is creating an Atlas, with some smart UV mapping you can avoid this all toghether. There are plenty tutorials for this online.
Otherwise, write a custom fragment shader, but that might be more work then you are looking for.

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Palm leaf creation
I'm trying to make a tropical island environment in unity, so for that purpose I want to model a palm. I want the whole scene to have a cartoonish look and feel to it, so I am going for something like this:

What I'm struggling with is how I can make the leaves. Does anyone have a link to a tutorial on how to make leaves such as these?
- I can't make the leaves bend as they do here.

I just don't know how to do it. I don't know where to start. Do you have any tips on how to model the actual leaf?

As we can see on the picture, the leaf's lowest point is the middle line, so I guess I would have to have a straight edge from the beginning of the leaf to the very tip. Right?

Start with some beginner tutorials, learn basic modeling methods, UV unwrapping, texture painting, basic modifiers and the most important thing, use google before asking question. There are tons of tutorials about foliage, leaves, trees and other nature creations. Come back here with specific and detailed questions. For your last question, how to bend them, I would suggest using B-bone. It will allow to have nice control over the leaf.

Start with a plane. Scale it into a rectangle which would fit the leaf inside of it. Select one end edge and scale it to 0 to make it a point. Then do on loop cut down the centre. Then do about 4 or 5 loop cuts down the middle. Select the edges each of those loop cuts made.
Press ctrl b to bevel and increase the segments to 2 and increase the offset to the size you want the bit where the leaf goes in to be.

Go on by one grabing the mid points of each bevel and moving it inward to make in in bits of the leaf.

Turn on proportional editing and set the fall off type to sharp. Drag up and down vertices until you have the curve of the leaf.

Merge the end points
Select the edge loop which goes from top to bottom of leaf. Disable proportinal editing and then grab it and move it down a bit on the z axis.

Then add a solifiy modifer to make the depth of the leaf and you are finished.
Finished Result:

The easiest way to bend geometry is to use the Bend operator - Shift-W in Edit mode, with the relevant geometry selected. The 3D Cursor position on the screen is important.

Right then, I just tested the bend operator and it works great.

But how would I go about modeling the leaf in the first place?

What I wold do is: Start with doing the outline of the leaf (a 2D plane). Keep in mind you have to leave a grid-like topology for the surface of the leaf, and avoid using n-gons, or this will complicate things later. Then apply the solidify modifier to give it some thickness. after that you can use proportinal editing to bend the leaf in a smooth/natural way

What do you mean with grid-like topology?

that the faces that form the leaf are all quads (four vertices), and about the same size. In short, don't just do the outline and fill it with F, try to leave a nice structure in the middle.

Right, I just don't see how I'm going to do that.

I've been using blender for a while, but i'm not very skilled..
I looked up at couple of examples on how to make a nice topology, but I don't see how I can transfer that to my model.


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Texturing a crooked object
How would I go about applying texture to an object with a crooked edge?
I'm trying to make a hallway with oldschool style doorways (curvy archway-like doorways), and I'm making the doorframe as a object by itself. So I want the wall to cover up so there is not going to be any holes. But doing that, I have to make the walls crooked around the doorframe to cover up the curvy frame. When I try to apply texture to this, the texture isn't straight but looks very weird. So how would I go about applying texture to this? Or should I model it in a different way? In that case, which other way should I model it?

What kind of texture are you trying to apply? (image texture or procedural texture?). Can you post a screen shot of the "weird" result you are getting?

It's just an image texture. I can post an example, But I don't have the project file with right now.
Image: http://imgur.com/a/LzGgs

This will happen if you have a square UV map but non-square geometry. Study up on UV mapping and I think you'll find all your answers.

Can you me a bit more specific? What should I look for?

With the example image (with the bricks) I changed the object, THEN unwrapped it.


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Low poly/ cartoonish tropical island creation
So I'm making a game in unity sort of like Sea of Thieves, which has a cartoonish feel to it.
What I've done so far, is create the shape of the island in blender, and then save the model to a folder in my unity project. Then I used the Object2Terrain script to make a terrain with the shape of the island.
What I'm currently stuck on, is making the rocks and cliffs around the island. I want to create something similar to the rocks/ cliffs in this:

https://www.cgtrader.com/3d-models/exterior/landmark/tropical-environment-pack
But every tutorial I find when searching "low poly cliff in blender" turns out to be bad.
Does anyone know what I could do in this situation? maybe they have a tutorial I haven't found they could leave a link for?

https://www.youtube.com/watch?v=iP-ZAUA8Ga4 This might help.There are so many similar tutorials.

What i recommend is to use a tool called Bisect.
To do this,  subdivide a cube and apply Subdivision Surface to get a sphere-ish shape.
Then to reach the Bisect tool, switch to edit mode, press space, search and there you go.
Press F6 and check "Fill". You can basicly slice pieces from your mesh. Then continue bicecting, till you get the shape you want. Scale the object to perfect your work.
I hope this little tip helped you, if you have any other questions or problems, let me know.
Source: https://youtu.be/G2CdYFgrP84

I will definitely look at it! I think it was exactly what I was looking for!


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Bloating a cylinder
So I have a cylinder that I have extruded some other geometry onto. I need a way to bloat the vertical lines of the original geometry. Thanks guys!
I need to turn this:
/ \
|||

Into this:
 / \
( | )

One way is by using Proportional Editing (O):

Add extra geometry to deform by adding some loop cuts (⎈
CtrlR)
Enable proportional editing (O)
Select a falloff in 3D view > Header. I used the default, Smooth, but you might want to try some other ones and see what you like best. Note that you can change the falloff in the Redo panel (F6) after scaling in step 4.
Select the center loop cut and scale with S. Use  MW to adjust the distance at which proportional editing will affect other vertices.

This was exactly what I was looking for! Thanks for the graphic, it was super helpful.

For a quick modeling, I'll suggest to use the "Cast" modifier, with Shpere cast type selected.

but you have to limit the effect with a vertex group to keep the roof's shape.

Yeah, that's right! I thougth the roof was a separate object to be put above.


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How to snap two mesh
I have two mesh that are not aligned to the grid. How an I snap and merge these two shapes?
The first one is a cylinder, the second is a half sphere. They are at slightly different angles, but they both have the same number of vertices. If possible I would like to merge each matching vertex.

See answer to similar question - To work with their vertex, meshes must be in the same object.

Both Mesh are the same object. The link is very helpful, but I'm still having trouble aligning the circles flat face with the cylinders flat face. Is there a way to align both flat ends to the same plane?

Are they at same axis ?!

try this addon : http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/3D_interaction/Align_by_faces

Yes, there is a built-in funtion.. see (another) related answer or this videotutorial

@Carlo The videotutorial did the trick! Thanks for the help!


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Can't export to .wrl after I have changed the pose.
I am able to export as .wrl files, but if I have changed the pose of my object, this option is not clickable. How do I solve this problem. I have tried to "Set as rest position" and "Convert to mesh from surface". But it dosen't seems to unlock the export option.
I am new to this program.
Thanks you for helping :)

The vrml export addon only exports the active mesh object, if the active object is not a mesh object then the export option is disabled.
After using the armature to re-pose your object you need to re-select the mesh object to be able to export it.


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How do I "Re-Randomize" Particle Emmission?
So I have two planes that are emitting particles with the default settings.
However, the "randomized" particle emission is exactly the same for both planes.
Is there a way that I can "re-randomize" the distribution so that this is not the case?
Thanks for any help.

You can change the "seed" value next to the emitter type selection:


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Render ONLY the Alpha Channel
I would like to render just the alpha channel in an animation, in order to use it as a matte when editing video.
How would I go about doing this?

I personally would make the background 100% black and the objects in your scene completely white (with an emission shader with R,G, and B = 1 and strength 1). With this method you have very short render times and you can use the resulting "binary" images as a factor input later on.
If you have other materials on you objects and don't want to change them you can use a separate render layer with an override material and disable the normal render layer.

Funnily enough, I happened to do just that before you answered. Thanks for the help!

There is a feature for this
The Combined Pass includes an alpha channel:

The Render Layers Node has an Alpha output for it:

If using Cycles make sure to enable Film > Transparent in the Render Context.

If using Blender Render make sure to enable Transparency in the Materials Context.

There is no need to change the material for all the objects in your scene!
There is no need to use ID Masks for this either.
There are cases where using an ID Mask will cause you problems, for example if your materials have transparency. Observe this tree. Its leaves are texture planes, so if you use an ID mask you will only see the outline of the planes.

If rendering glass with a transparent background in Cycles, see this.

Note that the OP wants to render just the alpha channel, this method requires rendering as normal as well which takes extra time.

@PGmath As far as I know that is a limitation of Blender's design in that the Image output and Alpha output are both generated from the same Combined pass. So unless Blender is clever enough to evaluate when the Image output is disconnected in the Render Layers node and not calculate it (I don't believe this is how it works, but haven't tested), then yeah, I think we're stuck with this. Maybe disabling some of Cycles' Ray Visibility settings for objects, reducing the sample count,  or rendering shadeless could be solutions if the rendering is going too slowly.

An elegant way to do it is to use masking and nodes.
First you need to select an appropriate 'pass index' in 'object'

Then activate the 'Object index pass' in 'Render Layers'

An finally activate the 'use nodes' option in the node compositor, adding an 'ID Mask' node, fill the appropriate ID of the object you want to use as a mask, and voilà !

The advantage is that you can directly render your scene dynamically, with the mask activated on it, without making all the background black, and can directly use a mask inside a full scene.

Change the pass index of all the objects in your scene to 1.

Go to the render layer tab, and uncheck all the passes except for object index.

Go to the node editor -> compositing tab, enable use nodes, and connect the indexOB output to the image input.

That's all. When you press F12, you will get this:

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


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Can I export a render of the material view mode?
So as you probably know, Blender allows different viewport shading mode (e.g. solid, wireframe, etc), and I was wondering if I could render / export an animation of the material view mode.
I want to do this in order to show the animation of my project without having to wait for a full render or using an extremely low sample rate (which, quite frankly, looks disgusting).
Is this at all possible?

Yes, it is possible, it is called OpenGL rendering. The leftmost buttons on the bottom of the 3D View will do this:

You will get a rendering of the current viewport, either a still picture (left) or the full animation (right). Just switch to Material view and press the button.


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Can I use Source Filmmaker models in Blender?
I'm a mac user, so I can't get Source Filmmaker, so I'm using Blender to make gaming animations. I found a whole bunch of Source Filmmaker models on the Steam Workshop website that I wanna use for my animations. Is there any way to get these models and load them onto Blender? Any help will be appreciated.

Blender only imports specific file types, although there are some addons to import an increased variety. If your file type is not included in the list, you will need to convert the file to one readable by Blender.

http://wiki.blender.org/index.php/Doc:2.6/Manual/Data_System/Files/Import


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Why won't Blender let me import .svg files?
I know this seems to be a repetitive question, but nothing seems to work for me. I am trying to make two ping pong paddles to put in Blender using Inkscape. I've watched the YouTube tutorials, and I know I'm doing everything right, or so I think. But when I press import, they don't even show up. I really need to know how to do this so I can make my ping pong animation. Thanks!
My pictures:

It works fine for me, however they come out very small initially:

Once imported and selected, you can scale them up with S. Once properly sized, it's also probably a good idea to apply the scale with ⎈ CtrlA.
Also remember to delete the default cube, otherwise they will appear inside it.

Thanks a lot! But when you import them, should they automatically be selected?

Never mind that. @gandalf3 When I scale them up, why does it remove all the color? Should that be happening?

It seems that your SVG has many layers stacked on top of each other. When you import this into blender, all the layers are in the exact same place, resulting in Z-fighting, which in turn is making the apparent color inconsistent and flickery. It's probably best to delete all but one of the layers (in either inkscape or blender), then use the Extrude setting to give it thickness (assuming that is what you want).

@VinceScalia This isn't quite true, the SVG imported sets the diffuse color, which is used in solid view.

Ensure the SVG import/export plugin is enabled. In the even there is no data returned check that your SVG will open in other compliant applications (e.g. GIMP, Inkscape). Compatibility can ruin your day with this one.


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render only the shadows in Cycles
Is it possible to create a matte shadow material in Blender Cycles?  For example, both 3DS Max and Maya have a preset material that only renders the shadow on the mesh.  It is great for applying to your floor when rendering to composite onto real footage.  I know that when you set up a tracking scene in Blender it automatically creates a node setup that composites the render on the real footage by using background and foreground layers.  But I have had problems with using that setup.  It would be simpler to be able to just apply a material that only renders the shadow on the mesh.
Is it possible to create that kind material in Cycles?

not yet https://developer.blender.org/D1788

As David already mentioned in the comments, there are plans for this in the future. As for now you will have to go with the compositing method described in various answers here: https://blender.stackexchange.com/search?q=render+only+shadow
The most comprehensible tutorial that I have watched about this topic is this one: https://www.youtube.com/watch?v=k7gKzgvFiGM


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Animate changing topology of a mesh
How can I animate a complete change of geometry in Blender? For example, I want a sphere to turn into a cube from one frame to another. This means the object that I am animating is not only changing the shape of the geometry, but also the face/vertices/edge count. I have viewed this question: Can I replace an object with another object and keep animation? After seeing that question, I was wondering if I could keyframe the change in mesh data. Maybe using a script?
The final result would be a stop-motion effect. I would model a different mesh for each frame. So each frame the object would have a mesh that was different from the last, like a fluid simulation which changes the mesh every frame.
Is this possible? A answer using scripts is welcome as well.

Does this answer help? Having mismatched mesh, I would try a mid shape that each morphs to/from, as in the cube morphs to a sphere, then is hidden and a sphere becomes visible and morphs into a monkey.

I want to do something similar, but the two shapes have a different number of vertices. It doesn't need to happen slowly either. The change needs to happen over one frame.

Over one frame, just animate the render visibility so that one object disappears and the other appears.

Related: https://blender.stackexchange.com/questions/80868/transforming-morphing-one-objects-shape-into-anothers


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Trouble with normal maps
Hello to everyone I have a small problem.
I used Smart UV unwrap to create UV map for a cave room and it work well when painting it in blender and using just diffuse map, but problem starts when I creating Normal map in CrazyBump and apply it to mesh in Unity all faces just becope bulging.
Can some one please help, maybe I should use another program to create a normal maps from complicated textures?
Here some pics that better describe my problem:

https://drive.google.com/file/d/0B1EvuMBz-PT6d25JR2hKeEhIcWM/view?usp=sharing
Here some pic with my UvMap

I assume the model looks totally normal when the normal map is removed?

@JohnsonMartin Yes it is.


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Particles facing wrong direction
I added the particles to a plan and they stood up as expected. I then applied a lattice to the plane and now the grass is sideways. Is there anyway to rotate the grass upwards again?

never mind. I changed the velocities and it fixed it


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Rigging deletes some of the mesh?
When I rig with automatic weights some of the model disappears?

Try every options of CTRL+A, also make sure you object is not already parented and if yes "remove parent and keep transformation". I hope this helps.


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What causes these black artifacts?
What did I do that caused the face of the mesh to glitch out like this? And how do I remove/fix it? I'm not sure if it is two faces ontop of each other?

As Cegaton said,

Z figthing... you have two or more overlapping faces

This happens when two or more faces overlap. When trying to fix this go edit mode TAB then press z to go into wireframe mode. The darker sections darker than the normal greys are where faces overlap. Follow those to the vertices and move the vertice. (you may have to move than one)
References
Cause of black artifacts in render?


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Find commands by name
I started using Blender and I am wondering if you can search for the commands by name, similar to what code editors like Atom are offering. I couldn't find such an option yet.

You can use F3. This will list the commands, and even show you the shortcuts (if they exist)
The shortcut is Spacebar for older versions of blender (< 2.80).

Also note that this is contextual: Pressing space on the UV editor will show UV commands, this also depends on object/edit mode.

@Kroltan Good note. I nearly put that in, but I wanted to do it properly, since its slightly more complicated then that, and didn't have time to test 'cause I was in a hurry.


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How to build a 3D spiral (not a helix)?
I've been looking for ways to build a 3D spiral in Blender, but every time I search for it, I find techniques for building a helix.  I'm not looking for a helix; I'm looking for a 2D spiral, extruded up into the 3rd dimension.
Does anyone have any pointers for creating one?

Could you illustrate what you want to achieve with some reference images?

@DuarteFarrajotaRamos Something along the lines of https://commons.wikimedia.org/wiki/File:Black_bold_spiral.svg

You should add that image to your question  See https://blender.stackexchange.com/questions/56396

Here is a tutorial for this:
https://youtu.be/-ckk8GVGv6o
Basically you use the shrinkwrap and the screw modifier to do this.

build a circle
use modifier screw and apply it
build a cone and scale and move it as you need it in the screwed circle
now use modifier shrinkwrap with object cone on your circle
scale z value to 0 so that you have "flat" screw

Hi. Please try to elaborate a bit more in your answer. Link only answer are not well accepted in BSE.

ok, i tried. but i really think an explanation video helps much more that 1000 words, because you can "live" see how to get there. but thanks for your recommendation.

This is not the point: the answer will mean nothing if the video become unavailable in the future.


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Move duplicated key frames
I have been searching heavily on trying to move the duplicated keyframes from say 25 objects and paste it to another set of 25(and doing so to copy to over 100 objects) I have been able to copy a single objects keyframes to multiple objects and duplicated multiple object keyframes but without being able to cut them and paste somewhere else. Is this even possible? Thanks


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How to offset or loft surface maintaining cross-sectional area?
I have this surface (blue) which I would like "offset" inwards (yellow) while maintaining the same cross-sectional area (red). Loft is probably the correct method, since the cross-sections can be defined. Is it possible to create a script for this in Blender?


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Exporting from blender to Marvelous designer?
I have a character with an animated armature.
I want to export it to marvelous designer5, with animation.
What would be the right process?

Try the autodesk FBX exporter. ;3

What formats can be imported into Marvelous Designer 5?

@Samoth - MD5 can take animated OBJ and FBX.

@Tavuk - you mean export FBX from blender than use the autodesk exporter? Or is a blender addon? And does it require baking the animation before exporting?

Thanks everyone. I exported Collada and MDD (needed to turn on MDD export in addon manager). Imported them to Marvelous designer and animated, than exported the same to Blender - Collada and MDD.


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Constrain object to bone (without rigging)
I am trying to connect a gun to a hand bone that is part of a rig.
I tried using Constrain position and Constrain rotation, but it keeps popping off to funny places.
My process was - Align object origin with bone. adding the constraints - with offset (The gun is rigged to the palm bone, and should rotate with offset). Changing Space to local space.
Than when the rig moves the gun flies off

Constraining an object to a bone is rigging.

Use a child of constraint

@RayMairlot - I refer to rigging as the bones and body rig. I want to attach an object that is not part of the body or bones.


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Undo isn't working correctly?
When I push undo it seems to go back too far? How can I set it to go one step at a time? I don't belive I changed any settings.

Related - http://blender.stackexchange.com/questions/35975/why-cant-i-get-my-undo-history-back

Make sure you are undoing in the edit mode. Undoing in the edit mode will undo individual steps you made while editing your object (eg. moving vertices, extruding faces...). Undoing in object mode will undo every change made to that object while you were in edit mode.


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Animation fade to black?
I'm making an animation and at the end I want the screen to fade to black. Is there a way of doing that with an animation? Or do I have to first render the animation and then re-open it when it has been made into an MP4 and then import back into the video editor, add the fade to black and then render it again in the editor? That seems like a lot of work for something so simple.

I just had a thought. Putting a big black invisible cube over the camera and then animate the cubes transparency to 1 towards the end? ;D

What does VSE stand for? Is that Valve Source Editor? That's what I know it as ;D

when you said render them as an image sequence did you mean render them all as PNG?

cegaton is saying that it's best practice to render out as image sequences initially, regardless of the image file format.  You can always assemble the images in the VSE later to convert them to a movie format.  It can be PNG, or any minimal loss image format, such as tif.  This is partly because this can minimize the picture quality loss normally associated with various video codecs at an early stage of rendering, and if Blender/your computer crashes during rendering, you can pick up where you left off if those images have been saved to your HD.

Fade-to-black can be achieved in Blender if you feel like third-party video-editing software is not optimal, or the most succinct.

Assemble your image sequence/movie file into the Sequencer.
Scrub to a part in the timeline where you'd like to begin fading to black.

Goto to Sequencer menu, click Add -> Effect Strip -> Color.  (It defaults to Black, but you can make it any color).  Note this strip should be on top of your image sequence/movie file.

Select this color strip, and hit N to examine its properties over on the right.
Find the Opacity settings just in the Edit Strip section.
Scrub to the beginning of this Color strip.
Set the opacity to 0.  With the cursor over top of the slider, hit I to keyframe it.
Scrub to the end of the Color strip.
Change the opacity, this time to 1.0, and with the cursor in the slider field, hit I.  The color's opacity is now interpolated over the duration of the strip.

You can also fine-tune the interpolation like any keyframe by opening this strip in the F-Curve editor.  Happy editing!

...That's very true!  Fading to 'pure' alpha translates to black in video output anyways :P

I don't think this really answers the question. Muly's question is to do a fade from it's 3D scene directly to black. Not to do it on images or movies.

It is possible to fade from a 3D scene with animation to a black screen thanks to scene strips, but to do that you need to create seperate scenes in your blend file.

One scene containing your 3D scene
One scene in which you will do the video editing

You can create your scenes at the top right corner above the Outliner:

Then select your video editing scene and go to the Sequencer. Click on Add > Scene > select your 3D scene.

Add a new Color strip. Click on Add > Color. Then right click on the Color strip > Fade > Fade in


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Lock face surfaces to each other?
I Want to run this along the surface of a face and then rotate it on the Y and X axis how can I achieve this?

Could you please clarify what to move and rotate along what ? As it seems to be you want to grab face which contains selected edges - but where ? And what are you going to rotate ? It would help if you mark steps on your screenshot.

You can "snap to face" :

Then move each vertice to the face :

And have this result :

But it wont automatically rotate or anything.
For "rotation" or other smoothing effects on the shape, this is to be done manually (I am quite sure there is no other way to do it, except if the rotation aspect is clarified in the question).


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Separate parts of the mesh will not stay with the rig
I have a character that I am currently trying to rig, and he has an object attacked to his shoulder. The problem is, I cannot for the life of me, get the object to stay above his shoulder while he raises his arm. It goes from this:

To this:

I've tried making seperate bones for it, re-rigging, re-assigning vertex groups, and a bit of weight painting (not very experienced with it).
This question may be a duplicate, but none of the other questions here seem to work when I try it. Thanks!

Since I can't add more than two links, here is my blend file: https://www.dropbox.com/s/m71ru124gmpe3w4/LowLevelMedievalWarrior.blend?dl=0

It's working fine for me. Maybe try restarting your Blender or your computer?

Well, if worked, for some reason. I remember restarting blender many times yesterday, but it did nothing. Maybe it was the computer restart that solved it. Anyways, thanks! I would've never though restarting my whole computer would solve it.

Glad to help out!


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Animations Disappear When Loading Up Blender
So, I was working on some animations the day before, and I saved my file and clicked the F in the action editor next to the ones I wanted saved (There were some other animations that I didn't know how to delete), and went to bed. When I woke up the next day, I started up the file, and all of my animations were gone. Does anyone know why this is? Is there some sort of way to save your animation, or is that what the F does, even though I pressed it?
By the way, I got then back by re-loading my old save file, I just want to know why that happened. Let me know if you need any extra details. Thanks!

Did you save after pressing F next to the animation tracks (as I understand you mean either NLA strips or actions in Action Editor) ?

Yes, I press F, looked at the animation a bit, then saved my file.

Try reloading your saved file, instead of using the autoload last session, which should be the same, but it isn't.

I already solved it at the time I posted it, but I just wanted to know if it was a bug or not. Judging from the answers, it was most likely a bug. Thank you!

The F toggle is something many of us animators have complaints about. Yes it has to be selected to keep Actions if you start a new Action. The F toggle stands for Fake User. When you start a new Action via the Action Editor the Action that you had is removed from the Armature. As objects can only use 1 Action at a time.
The correct way to use multiple actions is to use the NLA Editor. There are new buttons in the Action Editor's Header: Push Down and Stash. You can use those to save your Actions in the NLA Editor so that they don't get deleted.


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simple UV map on a cube gets rendering artifacts near edges
I'm using 2.69. I have a simple cube object, and have set up UV mapping for the face and sides, and added an image as texture via this UV mapping.
The UV map is simple, just a cross, and I've welded the points together rather that having separate rectangles for the front face and each side.
All normals are facing outwards.
When rendering, I get artifacts near the edges, that show part of the hidden sides through the front face (bottom and right of the front face).
The cube is a simple cube, no subsurf or anything fancy.
What is wrong here ?
(the artifacts show here as black, if I disable shadows I see the hidden faces instead.)

OK, I could eventually solve this. Seems with a camera at 50mm focal length artifacts occur. Set focal to 100mm and moved camera, no more artifacts.

Make sure you answer your question down below

I just did above, what do you mean ? (not familiar with the site)

Just like people answer your question, you can answer your own. Scroll down on whatever device you are using, and choose answer question or something in between the lines of that. It's at the end of the comment section.

mh, whatever ? very non intuitive interface, sorry.

No problem! It's just good to increase reputation

OK, I could eventually solve this. Seems with a camera at 50mm focal length artifacts occur. Set focal to 100mm and moved camera, no more artifacts.


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Blender doesn't render Cycles with GPU?
I was messing around with effect and when I went to start a brand new scene to render something that doesn't use effects nothing shows up until I switch render with CPU?

As of now, you need a CUDA capable card in order to leverage GPU renders reliably.  OpenSL for AMD cards are hit or miss right now.  The rendering guide also suggests that your card may not have enough memory.
https://www.blender.org/manual/render/cycles/gpu_rendering.html

The scene I am trying to render is a couple of MB and my GPU is a GTX770

It worked fine before I started using effects

What you mean by "effect"? For example, rendering  "smoke and fire"? Or what? Older Blender versions can't use volume shaders when "Attribute" node is connected to shader's "Density" input. You can also check "Feature Set" in "Render" tab and try both: "Supported" and "Experimental." BTW: did you see your graphic card in "User preferences" -> "System"

Of course you have to turn it on in the User Preferences under System via CUDA button (Cycles Compute Device). The Camera Render Device on GPU Compute pull down is grayed out if not enabled.
There are other GLSL options that speed up subdivisions for animation morphs and that is also turned on per object.
It seems the CUDA setting is not saved with the file, and you have to remember to turn it on manually.


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Edges with no handles?
I used the bezel tool and then some of the vertices were inside the model so I merged them so ones that were on the edge and it ended up creating some odd lines that aren't attached to any edge handles?

Those aren't precisely "edges." Think of a sheet of paper that only has four corners. If you put two opposite corners too closely to each other, you get a fold. That's basically what's happening here. Choose "Face Select Mode" and select one of those faces. You'll notice that the selection goes across that edge. That's because it's just a "fold" not really an edge.
Behind the scenes, the best-kept secret of CGI is that *everything * is triangles. You never actually have a quad, you just have two triangles that orient themselves differently, to accommodate a given scenario. And at render-time, everything gets triangulated, anyway.
If you can find the related vertices, you should be able to unfold that face into something that's a bit more reasonable. The other option is to select the two verts that are connected by that fold and press j. This will split the face and create a real edge, and that might help it make a bit more sense.


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Quicker way of adding faces?
I am trying to face these into wedges. Is there a faster way of doing it?

If the spacing are even I guess you may use an Array Modifier for that.

Select the prism and press P to separate it. Being in Edit Mode add an Array Modifier to the prism and set up the proper relative offset values. Check the Wire and Draw All checkboxes in Display panel of the Object Data header to help you match the prisms with a grid segments properly. Increase the modifier's count number and apply it. Join meshes with Ctrl+J. In Edit Mode select one of the edges as pictured below, go to Select-->Checker Deselect, increase the offset if needed and delete selected edges to cut the holes for prisms. In the end select the whole object with A, then press W-->Remove Doubles. You may also recalculate normals with Ctrl+N.


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Reverse an edge split?
I applied an edge split a while ago on my model and now I want to separate parts of it. It's going to take me a long time to individually select each face because none of the edges are touching the other. So I can't use some of the auto-select features in Blender...

Enter Edit mode > Select All > Press W > Remove Doubles

You can Tab into Edit Mode, key A once or twice until everything is selected, key W to open the Specials menu and select Remove Doubles.


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Export select pieces of a model?
I was wondering of there was a way to export a piece of the model instead of having to delete everything in the scene and then saving it and then undeleting everything again? Kind of like a select export.

This has been asked countless times before http://blender.stackexchange.com/questions/55913/is-it-possible-to-export-a-single-object-from-an-entire-scene/55915#55915 or http://blender.stackexchange.com/questions/56800/can-you-export-stl-file-from-one-object-in-one-layer

After selecting the objects you want, go to File -> Export. In the bottom left corner, you'll see a panel labeled "Export [name of file type]". There, you can click a checkbox labeled either "Selected Objects" or "Selected Only". The .ply, .stl, and .bvh files don't have these options. For example, here's the "Selected Objects" checkbox when you export to .fbx.


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Blender rigging while handling cloth collision
I have a character whose legs are draped in some cloth. I rigged the character and parented the rig to the character mesh and the cloth mesh. So when I move the rig parts, the corresponding body parts move and so does the cloth. When I move the leg of the character, the leg and the cloth draped on it , both move. However, the leg penetrates through the cloth after some point. Is there a way to fix this? I want the leg to push the cloth, and never penetrate through it.

I would try increasing the collision quality and maybe the distances.


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Previewing single lights in blender (cycles)
I am looking for a way to quickly disable all but one emission source on a scene to gauge how much of an impact it is on the overall scene.
I can hide other light emitting objects and change environment to black and then unhide all but what I'm looking for is a single shortcut. Like for example, Ctrl+Shift+Click on a node will preview just the node (with the Node Wrangler addon). I'd like to be able to click/shortcut on an object and have only its emission shown.

If lights you want to hide are of lamp type you can control them via Lighter's Corner in the Scene tab. If those are meshes with Emission shader that won't work and you can do that only by hiding those meshes via Outliner.


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Blender 2.72 No Cycles Hair Rendering/Settings Tabs
I have tried blender versions from 2.69 to present and have yet to see the Cycles Hair Rendering or Settings Tabs.
My steps
1.  New blender project with the cube present
2.  Go to particles and hit +
3.  Choose Type: Hair
and no Cycle Hair tabs??
My crazy cube hair renders just fine, but the Cycle Hair tabs are never visible.  Am I missing a setting somewhere?

Perfect!  That is what I was missing!!  Thank you!!!

If you look at the top of your screenshot, you will notice that the render engine is still set to the Blender default, which is Blender Internal. You need to select Cycles as the render engine.

Now all the settings appear as expected.


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How to pan UV map with mouse movement in UV Editor

Like the snapshot shown above, I have a selected UV map I wish to align to my texture. The only way I know is to adjust the UV Vertex configuration (located on top right UV editor view) by dragging mouse over it. Doing so makes the process very slow and inaccurate. It will really help speed up this tedious process if I can just pan it with direct mouse control like I do as I would move objects. Is such control possible?
Thanks!

Please see the Mike Pan's answer. He knows how to pan ;). In addition, pressing 'CTRL'+'MMB' and moving the mouse in any direction you can precisely zoom in and zoom out in UV Editor window.

You can pan around the UV Editor(and any other 2D view) with the Middle Mouse Button.

The function I am looking for is translate, found on the left toolbox panel, keyboard shortcut is G.


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I cannot get the grease pencil to render
I want to draw an image on top of an object I have created with the grease pencil.  When I then select render the object will appear, but it will not show the lines I drew with the pencil.  How can I get the grease pencil lines to show up in the render?

Could you add an image showing your problem?

I've tried cycles render and blender render.  Showing a picture of the problem would just show an object with grease pencil lines on it in the blender edit mode and that object with nothing on it in the render image mode.

It seems that at versions of Blender prior to 2.78 the only way to directly render the Grease Pencil is using the OpenGL Render option - since this effectively renders the scene as it would be viewed in the viewport.
However, in the Grease Pencil panel there is a Convert option which can convert your Grease Pencil layers into a path or curve. This can then be used to generate geometry (eg, by setting a Bevel Depth in the curve properties) and this can then be rendered.

It does appear that there are plans for a significantly improved Grease Pencil at later versions as detailed here https://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.78/GPencil and this includes an additional GP_Layer when rendering OpenGL to multi-layer EXR.


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I'd like it to move nearby vertices slightly when I edit a vertex
When editing a mesh, I can select a vertex and move it, and it moves independently of the other vertices. However, I'd like for it to move nearby vertices with it, and the pull drop off with distance. For example, if I could select the vertices at the corner of the mouth and move them around, slightly modifying the upper lip, chin, and cheek slightly.


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Why do some meshes have a diagonal line through quads?
I imported a FBX of a table. It is mostly various shaped boxes. But the rectangle faces have an edge running diagonally from 2 corner vertices. In screenshot, it shows one on the top of the table. What is the diagonal edge? And why is it black, when the other edges are light color?

"But the rectangle faces have an edge running diagonally" It is not a rectangle then, it is two triangles.

FYI - the reason the "triangle" edges are black while the rest are blue is that the blue edges appear to be marked "sharp". You can clear it (if you wish - may not be intended) by selecting the whole mesh in edit mode, right click and select "clear sharp".

@DuarteFarrajotaRamos -- thank you -- sometimes one does not recognize the obvious until it is pointed out by another (I find it more often as I get older :) )

@ChristopherBennett -- thank you -- so, whoever made this fbx used 2 triangles instead of a rectangle, and marked some edges as "sharp" but not others. I wonder if there is a name for this technique / approach?

It looks like the mesh was triangulated (or at least portions of it were) for some reason. If it's not the whole thing (ie, every face is split into 2 triangles), then I can't guess the reason for it. Often meshes are triangulated on export (and are almost always triangulated on import to a game engine), but usually it's the whole thing, not just "sections" of it. However, blender prefers quads, so if you're planning on using the mesh exclusively in blender, you may want to get rid of them. Also, marking "sharp" is often used to keep edges "tight" when smooth shading or using a subdiv modifier

@dl I work with a lot of CAD models inside of Blender, many times Cad models give you this result, triangulation everywhere and sharp edges everywhere... Maybe it is fbx itself because CAD models have no real topology and once they export it to fbx it makes these lines automatically... The thing that may help you is command called Tris to Quads, press F3 and search for it in edit mode with all faces selected

@MikoCG Thank you for extra insight (and C Bennett too). I think it may help with avoiding 'impossible quads', when the 4 vertices are not on the same plane. If they are converted to triangles, the 3 vertices establish the plane, so the face is not bent. The command to look for is awesome help -- would not have recognized that if I had seen it in the Menu or docs.


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Pose mode moves bone before clicking 'g'
When I select a control in Pose mode, in order to rotate (or scale) I have to first click 'r' (or 's). To move it, I don't have to click 'g', I can move the bone immediately. However, I make a lot of unintended moves (like pose 'typos') because it will register a movement when I try to click off to deselect the control, or select a different control.
How do I change Blender so I have to click 'g' in order to move a control or bone?


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How to viewport rotate around model's nose instead of model's center?
In Preferences, I have ticked Navigation > Orbit & Pan > Orbit Around Selection. It orbits around my humanoid model, but the rotation point is somewhere in the middle of the mesh, in the hips. How can I change the rotation point to be the model's nose?
When it rotates around the hips, if I'm working on the face, the model sometimes rotates the head towards me and away from me really fast. I would like to change the rotation point to the nose or center of the head, it would make it easier to control.
I have tried setting the object's origin to the model's nose, then select Individual Origins in Transform Pivot Point drop down, but did not help.
Thanks in advance for any suggestions !!

What you say happens in Object mode, in Edit mode though the rotation happens around the selected face(s)

Thanks -- I was hoping it had it in Object Mode because I use that the most to look at the finished work. Oh well, guess I have to zoom out first.

Oof!! Right in the manual: https://docs.blender.org/manual/en/latest/editors/3dview/navigate/navigation.html#orbit
"Clicking a point with Alt-MMB will make it the point of interest: it becomes the central point which the view orbits around."
This gets me closer to what I wanted, including in Object Mode. If I Alt-MMB on the model's nose, it becomes much easier to control the orbiting.

Adjusting the preferred pivot point for orbiting can be done by going into Edit Mode then selecting the mesh and pressing the Numpad Del or Numpad Period key. This function is often called "Frame Selected" or "Zoom to Selection."


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Can I use orphaned OOTB brushes?
In my Blender files, I noticed I only have one brush for Texture Paint (and probably other modes). In view orphans, it looks like there are a lot brush presets. Can I add them to my set of brushes and use them? I tried to drag it onto my brush tool panel, but that did not work.

Also curious, if anyone knows, why they end up orphaned? I guess because they are not used; but doesn't make sense they get orphaned for lack of use when they were not offered to be used before orphaning.


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Video clip editor motion tracking masks overlay
This is the situation:

I have a video with the following image display on a tablet (you can see the video here video here
I want to substitute the image you see one the tablet in the video (green background with crossed white/black circles) with an object plane with an image
Mind that in the video background, there is the hand of the actress that overlay the screen of the tablet (so, obviously, the texture of the plane has to be alpha where the "hand-section" of the movie frames overlay the plane).

My .blend file is here. (the video file is not packed, I've already done some camera motion tracking/plane deforming work)
So, my question is:
- is there a more or less automated way / addon in Blender using which I can get my goal?
- any suggestions?
Thanks to anyone ;)

An automated way to replace the screen? That's difficult since each footage is different. Dependent on your shots, you could only try to speed up the whole process by using a planar tracker like mocha.

@poor .. thanks for your reply ... I will go with blender planar tracking tool

@cegaton ... thank you for reply ... I've looked the post your linked ... there it doesn't explain how to do if in the video there is an object overlaying the video section I want to modify ... but I found these that helped me
https://www.youtube.com/watch?v=v0U7XE9Sl-g -----
https://www.youtube.com/watch?v=IezDwsh30ag
Thanks anyway ;)


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Export the animation of one bone to .bvh
I'm having a hard time figuring out how to separately export the animation of a single bone into a .bvh file.
I'm currently working on a project with a MakeHuman body, but I only want the motion of the right foot, is this possible? And if so, how?
Thanks a lot

Create a copy of your animation, in the dopesheet select all the data you're interested on, Ctrl I to invert the selection, X to delete unecessary data. Export to BVH.


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Joining 6 .stl files together to make 1 file to go to a comercial printer
Firstly let me say I have never used Blender before so I'm a total innocent.
I have 6 .stl files for 2 Pi camera housings made up of 2 and 4 files each.
I have been told if I can incorporate the files into 1 or 2 it will make the process much cheaper,as I'm using a commercial print company. So my question is can I start a new project, import each file individually and join them together to make 1 .stl file.

My guess is all you need to do is import all STL files into the same Blender scene and reexport them into a single STL file all together. Making them cheaper probably requires some optimization so it consumes less material and prints faster. Having objects close together laying down as as not to stack up very high vertically, will also probably print faster. Not sure if print time is taken into account or not, but if it does it may well save a few bucks.

Hi thanks for your reply I'll follow the tutorial below which is roughly as you said

Yes, you can.   Use Blender to import and position all of your stl files.
Group select all of the objects (so that they are highlighted).

Use Object -> Join to make all of the individual items one object. The Object menu option appears at the lower left of the Object Mode screen -- if you are in Edit or another mode, you won;t see it...

Making sure the object is highlighted, use File -> Export -> Stl

You'll end up with an STL composed of multiple non-connected parts. Whether this is cheaper or not is an issue for your printer: It might take as long to rip and print, and will certainly require the same amount of material to output -- infact, maybe more.... since I am not sure whether the method you are using will add supports or connected sprues between the separate items that were originally the separate stls... But this process will give you an stl with multiple 'pieces'.
Shout if I can assist.

Thanks for your detailed tutorial I'll follow it to the letter looks like this is  what I need. All the stls are for the finished component no spruces. Again thanks Bill

Well that was easy took about 10 min to do I'll send the file off and see if that's what they want or if I need to insert spruces. If I need to insert them I might be shouting out to you again....Cheers Bill

Just to let you know this saved me 1/3 from the original quote so thank you again

Glad to hear it!  3d printing is an amazing tool for designers, and Blender handles it so well...


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How do I fix this issue with weird faces?
When I'm modelling, I often end up subdividing a lot of edges and creating a lot of faces/edges. However, I often end up having a face that doesn't follow the edges or vertices assigned to it when it's created.

Can I get any help with what this is? or how to solve it? It would help a lot. Thanks :)

I would like to know how I could avoid this, it would be a great help since I have this issue a lot :)

In short, the face shown in your screenshot has 2 problems:

it is Ngon (face with more than 4 vertices),
it is non-planar Ngon (all its vertices do not share the same imaginary plane).

Chances are that you'd like to get rid of faces of this type and make sure they won't come up in future.
The thing is that there probably aren't any ways to avoid faces of any type in an automated way. It could happen that object is allowed to have Ngons on planning / modeling stage, but isn't on the final stage of working on it (when lighting / rendering). So no one knows if you are designing model or cleaning it. See When should N-Gons be used, and when shouldn't they?
The only viable option is to keep track of your topology which may be quite important for overall look of your model. So if it's a problem to have these faces, make sure not to create them! Do not subdivide faces while modeling (unless subdividing all of them); use LoopCut tool to add details along with managing edge flow orientation.

See also Topology Guides blog for great tips about modeling.
A lot could be written about different ways of modeling while preserving topology as good as possible, but generally 2 global principles should be listed:

cleaning up the model in the end of modeling stage (this could include retopologizing too);
modeling with quads or quads-tris only from the beginning.

While second comes mostly with practice, the first could be achieved with some tools which already exist (keep in mind that these tools are meant to be used for finding Ngons in meshes and finding / repairing non-planar faces in particular).

Default tools for mesh Clean-Up in Blender

Split Non-Planar faces tool will split adjacent faces if they are present and thus will show you where are they;
Degenerate Dissolve might help in deleting geometry which is not preferable like zero-area thin faces.

Mesh Lint addon

Check for Ngons in mesh with enabling adjacent option in Properties editor > Object Data > MeshLint rollout.

Mesh Analysis

With Distortion enabled you can preview faces which are not flat (non-planar, like one on your screenshot) and possibly can cause distortion of texture / shading artifacts etc.

See also:
How to flatten a non-planar face to a targeted plane?
How to make all quads or ngons on your mesh planar (2d)?
How to flatten a face to avoid distortion (make an ngon planar)

In Edit mode, Ctrl + Tab, choose Vertices, there would be a vertex where the pointy face is, select that vertex, then X, choose Dissolve vertices, this will remove this vertex non distuctively.The reason you are getting these artifacts is probably hitting a button by mistake at some stage, keep in mind that some operations are multilevel, as extruding by hitting E for example, right clicking before confirming would look like cancels the operation, yet it only cancels moving the selected sub-object, but kept the copy, you need to undo in this case, several other operations act the same.


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Visualize some edges of a mesh with Blender (or MeshLab)
Here's my problem :

I have a triangle mesh in .PLY file.
In this .PLY file I have a description for edges :

element edge N
property int vertex1
property int vertex2
property uchar red
property uchar green
property uchar blue

I want to observe the color of the edges. Actually, there will be just one color to tag some of the edges of the mesh.
Is it possible with Blender or MeshLab ?
Thanks.

Blender doesn't render mesh edges, it only renders faces. While you can display the mesh edges in the 3dview and see them when using an opengl render, they will be one colour for the object, normally black or orange when selected while grouped objects will be green when selected.
There are some ways to get around this, one is to use a wireframe modifier that turns the edges into a tube like mesh structure.
You can then apply the modifier and select parts of the mesh and assign different materials as explained before.

To get both outline and faces you simply need to duplicate the object and turn the duplicate into the wireframe tubing.
I don't know if the ply importer will maintain any edge colour information, but you may be able to adjust it to automate the process if you need to work with a complex mesh.


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Noise in rendered image
I have created 3d model of a little boy but when I render it there are small points on the model what can cause it? There is a plane with material of emission.

Those are fireflies. Mostly because fireflies are light pixels, lighting will help make them less visible. Are you using Cycles? If so, I can help you improve your render.


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Rigging Error "Bone Heat Weighting: Failed to find solution for one or more bones"
I want to connect bone with the mesh with automatic weights but when I press Ctrl+P->With automatic weights it brings me this error , I tried to remove doubles but the error hasn`t gone .

Last time I had the same problem,this tutorial helped me. https://www.youtube.com/watch?v=IZPqxADetWE

Could you upload the .blend file to make it easier to assess http://blend-exchange.giantcowfilms.com/

I found the problem for me... I scaled, rotated and moved the mesh and the skeleton in object mode. Meaning the object center of both of them doesnt match. Set the position and rotation in object mode on all axis to 0 and set the scale to 1 (for both skeleton and mesh) Go to edit mode move your mesh and rig around and make everything fit. Now go back to object mode make sure position, rotaion and scale are still the same for mesh and skeleton... if so you should be able to parent your stuff properly.


text:
How to change direction of view by Python?
I have an idea.
For example, I have three 3D View areas. And when I change view in the biggest one, in another 2 views direction must change too.
For example #2, if I press 1 when the biggest window is active, then in 2 other 3D View windows view direction must change to Top and Right. And if I press 3 in biggest window,  directions of view in other windows must change to Top and Front.
Now I just have access to all areas by using this code
    bpy.context.window_manager.windows[0].screen.areas

I hope you understand me, sorry for bad english.

Register a new operator that changes the views to your liking and bind it to a hotkey.
You can calculate the size of an area by multiplying width * height if that marries up with your idea of area size:
import bpy

class VIEW3D_OT_viewmulti(bpy.types.Operator):
    """Adjust 3D Views based on size (required 3)"""
    bl_idname = "view3d.viewmulti"
    bl_label = "Change multiple views"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):

        areas = sorted((area for area in context.screen.areas if area.type == 'VIEW_3D'), key=lambda a: a.width * a.height, reverse=True)

        if len(areas) < 3:
            self.report({'ERROR'}, "Not enough 3D Views (< 3)")
            return {'CANCELLED'}

        ctx = context.copy()
        ctx['area'] = areas[0]
        ctx['region'] = areas[0].regions[-1]
        bpy.ops.view3d.viewnumpad(ctx, 'INVOKE_DEFAULT', type='FRONT')

        ctx['area'] = areas[1]
        ctx['region'] = areas[1].regions[-1]
        bpy.ops.view3d.viewnumpad(ctx, 'INVOKE_DEFAULT', type='TOP')

        ctx['area'] = areas[2]
        ctx['region'] = areas[2].regions[-1]
        bpy.ops.view3d.viewnumpad(ctx, 'INVOKE_DEFAULT', type='RIGHT')

        return {'FINISHED'}

# store keymaps here to access after registration
addon_keymaps = []

def register():

    bpy.utils.register_module(__name__)

    # handle the keymap
    wm = bpy.context.window_manager
    km = wm.keyconfigs.addon.keymaps.new(name='3D View Generic', space_type='VIEW_3D')

    kmi = km.keymap_items.new(VIEW3D_OT_viewmulti.bl_idname, 'SPACE', 'PRESS', ctrl=True, shift=True)

    addon_keymaps.append((km, kmi))

def unregister():

    bpy.utils.unregister_module(__name__)

    # handle the keymap
    for km, kmi in addon_keymaps:
        km.keymap_items.remove(kmi)
    addon_keymaps.clear()

if __name__ == '__main__':
    register()

Hotkey in above example code is CtrlShiftSpace.


text:
How come my keyframes don't show up in graph editor?
I am using a Python script to generate keyframes for materials(changing the strength of emission node over time). I use the same script to set up keyframes for material A and material B. I can see keyframes for both material in NLA editor but only keyframes for material A show up in the Graph editor. Did anyone have the save problem? Is it a bug or did I do anything wrong? Thanks for your replies in advance.

Both the dopesheet and the graph editor have some options for what they display.

With the cursor button highlighted, only selected items will be shown, for a node tree this means the node that has keyframed values needs to be selected. As you are creating them by script you can set the select property of each node as you create them.
eg.
bpy.data.materials['Material'].node_tree.nodes['Emission'].select=True

The ghost allows you to see items that are hidden, that is the object containing the keyframes is hidden in the 3dview.
The filters list allows you to show or hide based on what data blocks have the keyframes. By turning off the node symbol you won't see any keyframes from nodetree items.


text:
What is the best way to animate the camera path?
I'm modeling a car driving along a road(speeds up, slows down, and stops at traffic lights to wait till the lights turn green, etc.) What is the best way to animate the camera path for the following scenario?

The camera starts moving from point A, and it takes 500 frames to get to point B. During this 500 frames, the camera first gradually speeds up, then moves at a constant speed, and finally slows down to a complete stop at point B.
The next 50 frames, the camera will stay at point B.
From frame 551, it takes another 500 frames to get to point C from point B. The camera experiences the same motion as described in #1 (speeds up, constant speed, slows down, then stop.)
Again, the camera will stay at point C for another 50 frames.
Point C to D is a curve path ( added using Shift + A -> add path). I want the camera to move along the path from frame 1101 to frame 1200. The camera should have the same motion as before(speeds up, constant speed, slows down, then stop.)

What is the best way to animate the camera path in this case? Is there any Python scripts available and can be applied to case like this? Thank you all in advance for your replies.

Use a Follow Path constraint and animate the Offset

The path curve starts only from C to D(shown in red). I wasn't able to make the camera follow path starts from frame 1101 and when I tried Follow Path constraint, the camera doesn't rotate right.

You can edit curves . .

http://wiki.blender.org/index.php/Doc:2.4/Manual/Constraints/Relationship/Follow_Path

Relevant for your question: http://blender.stackexchange.com/questions/23675/how-to-make-a-follow-curve-animation-more-harmonious/23676#23676

This will help with your animation: http://blender.stackexchange.com/questions/23854/


text:
How can I change the color of a material using Python script?
I'm modeling LED signs with different frequencies and duty cycles to animate flickering LEDs. It is impractical to manually set the color of LEDs at all the keyframes for each single LED, since I have more than 20 LEDs and they all have different frequencies & duty cycles. I think it will be so much easier to use Python script. Here is the description of the problem.

Use the pictures above as an example. I created an object and emission shader "material 1" manually. "Material 1" only applies to the circle in the middle of this object (as shown in (a)).
I want the color of material 1 to be red from frame 1 to frame 10. From frame 11 to 30, the color will be black(as shown in (b)). From frame 31 to 40, the color turns to red again, then black from frame 41 to 60. As you can see from the first picture, the same pattern happens over and over again and continues to the last frame.
I was wondering if I could use Python script to simulate this instead of manually set keyframes for all the LEDs. Thank you all in advance for your responses.

This is related: Control Cycles material nodes and material properties in Python
This is how you add an keyframe:
import bpy
# get the material
mat = bpy.data.materials['Material_Name']
# get the nodes
nodes = mat.node_tree.nodes
# get some specific node:
# returns None if the node does not exist
emission = nodes.get("Emission")
# set strength to 0.8
emission.inputs[1].default_value = 0.8
# add keyframe to strength at frame 1
emission.inputs[1].keyframe_insert("default_value", frame=1)
# set strength to 0
emission.inputs[1].default_value = 0
# add keyframe to strength at frame 21
emission.inputs[1].keyframe_insert("default_value", frame=21)

Now the intensity will animate from 0.8 to 0 in 20 frames


text:
How to manually mirror armature in blender 2.78a?
In all previous version, we used to mirror armature by copying one side, and then center 3D cursor to zero, and duplicate, and scale by -1. However I notice that in version 2.78, (correct me if I'm wrong) scaling -1 on x seems to work differently than before as it will caused unwanted rotation on bones. Is it happening to everyone else, and what do I do to prevent it?

Nevermind, I tried in 2.77, it still happens.

Yea, it's long lasting inconvenience in Blender, but it's easy to fix with pressing W and choosing Symmetrize.

As Mzidare said, you can try Symmetrize. Here's a mirroring technique that circumvents this problem:
You can enable X-Mirror, then extend from a central bone with E. The extension should occur symmetrically, and any changes to one should affect the other. I hope this helped :)


text:
How to edit shape keys with the armature deformation in needed position?
Maybe for all these years I've been missing something but, is it correct that in blender you just can't edit a shape key when the mesh is deformed by an armature? It's almost like a pleasure denial that whenever you wanna edit your shape key, your character model just snap back to rest pose, and then you're like: what was it that I'm fixing?
I hope someone can come and call me stupid and I've been missing something for all these years.

Do you use this button in modifiers?

I think, this is that you are searching for.

Oh GOD YES thank you you saved my pathetic life!!! I knew I was just too stupid to figure that out!!!

I found it useful to save my rigged pose in Stl and then bring it back to Blender to convert it to SVA.  It took me hours to figure this out.  I come from non tech background.


text:
Extremely Grainy Renders - Render settings help
I know this question is probably asked a million times on this site, but I can't seem to get a good clean render. I have my preview at 200 samples, a min of 3 and a max of 12 light bounces. I don't understand why it is still so grainy, are there any settings that will make a huge difference?
I'm still new to blender, so please bear with me.

There's not enough information to be able help you, could you add more details? How is your scene lit, what lights are present in the scene, what materials or shaders are you using, what are your world settings? 200 samples is generally considered low-ish for most scenes or for a final render.

This will likely be flagged as a duplicate question. But the quick answer is that 200 is very low samples. A pure diffuse material might get away with as few as 500, but for glass, you're going to need ~2,000+ depending on other settings.

My light source is just a simple Sun light so I could illuminate the render, I'm only using a diffuse shader and a glass one above it, and I haven't touched world settings so I would assume they would just be at default.

Please post your blend file so we can take a closer look.

This is most likely caused by the glass between the object and the light source. Sampling through glass negates a number of optimizations, which, depending on your scene, can have very drastic consequences. There are some approximations you can implement yourself to work around this. See this question: http://blender.stackexchange.com/q/10434/599

I have also had trouble reducing graininess. I use Blender to model buildings and graininess (noise) is always worse on interior scenes.
I don't believe there is one simple answer.
Certainly increasing the number of samples (to say, 1000) will help.
If your scene includes glass you should ensure you are modelling it correctly (so that Shadow rays see a pure transparent shader).
I have always found graininess to be most severe when modelling an interior lit from outside (through apertures). My intuitive understanding of what is going on (which might not be correct) is that the randomly chosen light paths 'bouncing' off diffuse materials have trouble 'finding' the light sources. One pixel will find a light source, a neighbouring pixel might not. Increasing the number of samples gradually smooths this out.
There are other things you can do also (caustics, clamping, portals) but I am afraid I don't know enough to advise you reliably on those


text:
What's Wrong with my UV editor?
I've been working on this scene for a long time now but as I tried to put a skydome in, it would keep denying me the ability unwrap the top half of a UV sphere. I tried doing the same thing in a brand new scene and it worked, but not in the one I am currently stuck on.
The UV editor is more of a rectangular shape than normal, which I believe is part of the problem. Basically I am asking how I can fix this so I can unwrap the top half of a sphere to create a skydome.

See http://blender.stackexchange.com/questions/9138/stuck-at-uv-mapping-mesh-doesnt-show-in-uv-window

You are looking at a render result. Click the "x" to clear it.

That helped a lot, it's the little things that get me sometimes


text:
How to fix grains within render?
I've been trying forever to find solutions to this problem.
When I render, my scene gets grainy under the influence of light and after searching the internet I can't find a proper solution:

I want to know how to get rid of the grainy-ness on the diffuse object under the light, and also the two random white pixels. I'm using Cycles, my sampling is at 4000 and my light bounces are set the limited global illumination.
P.S. Can anyone tell me how my GTX 1070 took 5 minutes to render this (and/or how I can render more efficiently)?

See http://blender.stackexchange.com/questions/39391/how-to-reduce-noise-in-a-dark-cave-scene

Turning up the AA Samples helps.

25 is decent, higher is better.
Glossy and Transmission tend to be noisy, so I turn those up.
I usually click render, then go watch TV.
If I come back an it looks OK, then I stop the render.
It only ever goes through all 64 passes if I fall asleep.


text:
How do I install makehuman in windows 8.1?
I downloaded these files;blendertools-1.1.0-all.zip, makehuman-1.1.0-win32.zip and mhx2-stable-025.zip, copied and pasted the three blendertools folders and the mhx2 import folder into the blender addons folder but when I open blender, makehuman addon is not appearing in the the preferrences. please help.
  Thank you

MakeHuman is a standalone application not related with Blender, you must uncompressed the downloaded zip file and run the executable inside. Only the import addon must be installed, and I believe Blender already ships with one by default, all you have to do is activate it in the user preferences

I'm voting to close this question as off-topic because this is a question about Makehuman, not Blender.


text:
How to add green screened footage to this scene?
I'm looking for advice on different ways and work flows for an animation idea. i want to get video footage of a human standing on the look out tower in my scene below (WITH) the 3d camera moving

1. tracking markers on a green screen, motion tracking the green screen, key out the green and then constrain the tracking data to the camera in the 3D view

is there any way to do this without a giant hollywood green screen studio?
how do i deal with scale? for instance i want my subject to be on the look out but the camera to be far away.

2. Adding a video image sequence with alpha to image planes and removing the alpha.

this would restrict some axis of camera movement but could in theory yield a decent result for some types of shots. Yes no?

Overall i'm rather confused. Any advice right or wrong would be appreciated as there is little info in this subject
Cheers

Cegaton has a great answer, but I would go about it a different way.
There it no reason you have to make a full 3D camera solve, and you probably do not have enough space to shoot for it.
What I would do is approximate it all. Animate your 3D camera first, then shoot the footage of your actor with the same motion in mind. If you are going for a medium to long shot, it does not have to be anywhere near perfect.
Now you do not need to move the camera in the same path, at all. Say all you are going to do is have the camera fly around the look out tower, then you could shoot the actor on a turn table, and keep the camera stationary on a tripod (and use a small green screen).
I would place an empty at the spot in the 3D scene where the actor will be, then in after effects use that empty's location to control the position of the clip of your actor.

Here I have a plane and empty selected, the empty is the empty I talked about earlier, which will serve as the position reference point.
The plane is nothing special, all it does is block everything in the scene that would be behind the actor. It has a holdout material. This is only used to get the elements in the foreground with a alpha channel so that the actor can be composited in.
The second time you render the scene, to get the foreground elements with the hold out shader plane, you only need to render the part around where the footage will be. Save yourself some time and use the Render Boarder CtrlB to only re-render the part you need (as shown in the image below).

This gif shows the different layers, to make up the composite.


text:
Perfect Machine for blender
i've been searching for the perfect machine for blender.. the highest rated production level machine,that break up mentioned on blender site.
I cant go so much in to technical depth of pc components. in some parts something is lacking and something is up to the mark . its difficult to chose. So my question is very simple.
If i buy Apple MacBook Pro – MJLT2 would that be the perfect machine for blender in all aspects.Would i be able to do every ting from sculpting to rendering pretty easily on that machine? Specs for the mac book are below.
• 2.5GHz Quad-core Intel Core i7, Turbo Boost up to 3.7GHz
• 16GB DDR3 RAM - 1600
• 512GB SSD Flash Storage
• Intel Iris Pro Graphics + AMD Radeon R9 M370X with 2GB GDDR5 memory

can u link me the one asked before?

I would say there are two criteriae for the machine: speed of the UI and 3D-tools and speed of the renders. For the UI you are very well covered. (I have been desperately sculpting with dyntopo on a 15-year old two-core no physical (integrated or other) graphics card (I had to virtualize an old OpenGL-compatible card). It was awful, but OK for the very desperate cases)
So everything 3D or UI, you are good. Then there is rendering. If you want to render with Cycles, you want to use a CUDA enabled (ie. Nvidia-brand) graphics card. There should be changes to this on the way, but for now that's the deal. So while you would have a powerful graphics card, you couldn't practically use the card for rendering.

thank you for your input.. any recommendations? i haven't bought that machine yet

Please, don't trust me. I just wanted to point out that flaw as quickly as possible.

And by "don't trust me" I mean: don't trust me for choosing a computer for you.


text:
How to apply material selectively on a single object for a downloaded 3d model
Hi I am new to blender and am trying my hands on creating a house from different 3d models imported from freely available websites.
So I downloaded a few study rooms and bedrooms from http://tf3dm.com/. However now when I try to apply texture specifically to (say) a bedsheet, it is commonly applied to all the walls and the floors and a lot of furniture around.
How do I unlink all these objects and apply materials specifically to individual components of the house?

No, this is not my problem. I found a solution to my problem here. The issue was the materials were linked to the data. When I selected object the issue was sorted. However do I have to unlink all the objects individually? Is there any short cut like Ctrl + A for select all in blender?


text:
Centre every object in relation to each other
For something so simple there are surprisingly little Google results, likely because I'm a noob and everyone already knows how to do this.
I have imported a Collada DAE 1.4 file, that I made in another 3D modeling tool, into Blender. In Blender, the model is shown very large, and it isn't centered at the origin. I want to start by moving the model to the centre of Blender's grid.
However, the model file contains multiple objects, and I'd like to keep it that way. I knew to centre an object, you can go Object>Geometry to Origin. The problem is that every selected object gets moved to the centre of the grid with total disregard for every other object around it.

I am aware there is some z-fighting going on, but I will fix that after my model is centered and scaled. Here's the model as it should appear. The 3D cursor is way off in the background behind the skydome, in its original position at the centre of Blender's grid, and I want the centre of this model to be there.
Here is how it looks when I select every object and do Object>Geometry To Origin.

Yes, everything is centered, but no longer is the model laid out the same way as before. Instead, every single object is now at the centre, instead of there being a sort of "bounding box" put around everything and centering the bounding box instead of each individual object. The wings, which were in its own object, are at the centre, and the tail, which was its own object as well, is now also in the centre - rather than remaining attached and being treated as if one object.
I could just combine every object using Ctrl+J. But I'd like to centre everything while keeping the objects separate.

Either select all objects, center the cursor with Shift + C and then use Shift + S > Selection to Cursor (offset); or if that doesn't work:

Select all objects with A
Clear their relations by removing parenting with Alt + P
Center objects origins with Shift + Ctrl + Alt + C > Origin to geometry
Now select all objects again with A and then Shift Select one last large object (like the ground or the scene background or whichever you want to be at the exact center of the world) by clicking on it to make it the active object
Press Ctrl + P to parent all other objects to that one
Now you can move that active "main" object to the scene's origin with whichever method you like more without breaking objects relative positions.

Either With Alt + G or with Shif + S > Object to origin or by manually entering or clearing coordinates.
You can then release the parenting if you no longer need it afterwards.
Edit: Have in mind that this may break any meaningful relationships you might previously have between your objects
P.S. Offtopic: Kudos for having Vivaldi browser installed ;)

Hmmm, I don't get an option for Origin to cursor when I press Shift+Ctrl+Alt+S, instead it opens the Shear panel. I should mention I'm using Blender 2.74 and I havn't edited my hotkeys.

Oops my mistake, fixed key combination

To move an object to the center first press "Shift+C"
this will move the virtual cursor to the center.
Then right click the object
and press "Shift+S" and select "selection to cursor.
Another way of going it is by first selecting the object with a right click
then press "G"
then press down on your scroll wheel and move the mouse
in the direction you want it,
release the scroll wheel, move the object and left click to confirm.
https://www.blender.org/manual/editors/3dview/transform/grab.html

So the object has to be centered manually? Pressing Shift+C just seems to zoom out the camera to frame the model, and then pressing Selection to Cursor creates the same problem I described above. Every object is moved to the center, but not in relation to one another's previous position.


text:
Cycles Node maps to image
How would i export cycles node maps and turn them into images?
I am trying to port a model into the Source engine and i want to have the same node maps. I looked everywhere and nobody has figured it out yet.

Yes, but when i tried it blender just exported a black image.


text:
How can I add a scale reference to the Z axis
Blender has a convenient reference grid with 1-unit squares, centered on (0,0,0) in the X-Y plane; I want something similar on the Z axis.
I know I can add reference images to the background, and I could create one manually for this purpose ... but having to go to a separate program and import a specially created image seems excessive when I just want a simple ruler to eyeball things against. My current workaround is to add several plane meshes to make a vertical line of squares that I can measure against - but again, it feels like there should be an easier way to do it.
Is there a quick and easy way to do this? Ideally, it would let me set a custom interval for the gridlines/ruler ticks, but I'd accept the standard 1-unit ticks if that's the best I can get.

have you tried the orthographic views? - they will show a grid in all three orientations. -- font, left, top ... back, right, bottom .

@zeffi I knew I'd end up kicking myself over this one. No, I hadn't thought of trying orthographic view, but that gave me what I was looking for. If you want to add that as an answer, I'll give it the tick; either way, thanks!

Easiest option
Orthographic views tend to be useful for this. Even if you're eyeballing there will be less distortion in the perception of location. Orthographic views will show a grid in all three orientations. -- font, left, top ... and their reverse: back, right, bottom. See the Blender manual for all options, and menus relating to this

Here Front, Top and Left are visible.
possibly interesting option
An addon called 'Chromoly Ruler' or just 'Ruler', is included in the addons_contrib. If you get blender from somewhere like builder.blender.org. It looks like this

It seems that this ruler is no more present in blender 2.79 ver. It is present until 2.78


text:
The character arm rotates the wrong way after 180 degrees
Currently, I am try to make a character rotate their arm by around 240 degrees. However, the rig decides to to take the shorter 120 degree way. Why does this happen and how can I fix this?

Thank you for posting that link. I found a solution after making an "in-between frame." I need to invert all of the values in the rotation section.

The answer turned out to be simple. For the arm to rotate the correct way, it simply had to have all of the bone rotation values inverted.

The values were previously,
W: 0.262,
X: -0.720,
Y: -0.604,
Z: 0.220,
but were inverted.


text:
Make light pass through solid object
Using Blender Internal, is there a way to make light pass through a solid object, such as a cube, as if it wasn't there? The cube of course would still be rendered.

Yes.
Go to the Properties panel > Materials tab > Options menu and deselect Traceable. Now, if, for example, you had a Cube with a Point Lamp inside, the point lamp would still affect the scene's lighting. You will, however, also have to have lamp(s) outside the cube to light it.

Also, consider looking at this .blend file. The cube in the center is the one with the lamp inside.

Thank you. I have no idea how I missed this.

@Tritofic Glad to help. I learned about it in the BlenderGuru subway tutorial a while back.

How do I do this inside of Cycles however?

@NaturalistUbuntu Use LightPath > IsCameraRay as the fac in a Mix Shader node with your material in the bottom input socket and a Transparent BSDF in the top input socket.


text:
Transfer particle cache from one file to another
As the title states, is it possible to transfer the particle cache of one file to another? I apologize if this is a duplicate, but I don't think I've found a relevant answer
I thought to use the blendcache folders created when saving to disk and using the External option to read from a folder, but it gives "No valid data to read!".

I'm not familiar with particle systems and cache but as far as i know, the cache is saved to the particle system container object by default. So without using the external option, you could try to append (File>Append) the blender file, and chose the emitter object.

I just tried this and although appending an object with a cached particle system brings over the settings, it does not transfer the actual cache, whether saving to disk or not.

I just tried with cloth cache and it worked. Are you sure? I'll try with particle right now.

So, yes, it work. Create your particle system, bake it without checking External. Save your file. Then append this object in a new blend file. I created two cache, one of them give the message "No valid data to read" but it work anyway. I have my two cache available and usable in the new blend file.

Alright, I just confirmed that this works, but without checking Disk Cache. It may cause memory usage issues in particle heavy scenes, but another solution I've found is to create and bake particle systems in both files with the same caching name, close the file that needs to be copied to, and copy/paste the files from the blendcache folder of the first file to the file that needs to be copied to.

I was investigating this recently and had to resort to reading the source code to figure this out (blender/source/blender/blenkernel/intern/pointcache.c and ptcache_filename()).  I was never able to find any documentation for the various idiosyncrasies.
When you create a Disk cache the files end up being named in the pattern %s_%06d_%02d.bphys.  The %s is a prefix; the %06d is a frame number;  and the final %02d is the index number.  For example: 537068657265_000231_00.bphys .  It turns out that 537068657265 is what happens when you convert the ASCII for "Sphere" to hexadecimal.
However, if you double-click on the item in the list of caches and give it a name that will be used as the prefix on the filename instead.  The fact that this defaults to blank makes it easy to overlook the fact that you can give the cache a name instead of using the hex-encoded name of the object the particle system lives on.
It is possible to use these files as an External cache, but it takes an extra step.  You provide the directory containing the files as the File Path, then you have to rename the cache item in the list above it to match the prefix of the files (for example 537068657265) .  If you do not rename the cache item from the default blank then it will look for files named like _000231_00.bphys (a blank prefix) and since they do not exist you get the No valid data to read! error message.

Alternately, you can rename all the files to have a blank prefix using a shell script like
for i in *.bphys; do
    o=${i#537068657265}
    mv $i $o
done

While not an answer to this question, the format of the bphys files is discussed in the answers to https://blender.stackexchange.com/questions/15577/how-to-extract-convert-data-from-blender-cache-files-bphys-into-a-human-readabl

Thanks, this confirms what I did with renaming the particle systems in both files to the same name and then copy/pasting the baked bphys files. It was also interesting to see how the file naming patterns worked without renaming any particle systems.


text:
Modal mousemove to change material slot index?
I've been trying to achieve this, but have no luck.
Here is an existing example in which can be easily modified.
I'd like to have this modal operation work for switching between material slot index. Any way of using integer values 1-10 so everytime you move your mouse, the active slot is changed to the next index, for example: 0 > time.sleep for half of a second and then switch to 1 and so on, but depending on mousemovent distance(delta). Thanks.
import bpy
from bpy.props import IntProperty, FloatProperty

class ModalOperator(bpy.types.Operator):
    """Move an object with the mouse, example"""
    bl_idname = "object.modal_operator"
    bl_label = "Simple Modal Operator"

first_mouse_x = IntProperty()
first_value = FloatProperty()

def modal(self, context, event):
    if event.type == 'MOUSEMOVE':
        if self.lmb:
            delta = self.first_mouse_x - event.mouse_x
            context.object.location.x = self.first_value + delta * 0.01

    elif event.type == 'LEFTMOUSE':
        # we could handle PRESS and RELEASE individually if necessary
        self.lmb = event.value == 'PRESS'

    elif event.type in {'RIGHTMOUSE', 'ESC'}:
        context.object.location.x = self.first_value
        return {'CANCELLED'}

    return {'RUNNING_MODAL'}

def invoke(self, context, event):
    # variable to remember left mouse button state
    self.lmb = False

    if context.object:
        self.first_mouse_x = event.mouse_x
        self.first_value = context.object.location.x

        context.window_manager.modal_handler_add(self)
        return {'RUNNING_MODAL'}
    else:
        self.report({'WARNING'}, "No active object, could not finish")
        return {'CANCELLED'}

def register():
    bpy.utils.register_class(ModalOperator)

def unregister():
    bpy.utils.unregister_class(ModalOperator)

if __name__ == "__main__":
    register()

# test call
bpy.ops.object.modal_operator('INVOKE_DEFAULT')

I'd suggest changing to the modal timer operator.  Set up the timer to match the sleep time.

I'm not so sure how to do that. Can you provide an example. Thanks.