text:
Why isn't the cube's collision properties working?

You can see the particles in the above image, but, despite the cube having had "collision" properties in the settings, it won't block the particles?

...and here's the physics settings I'm using.

Here is the .blend file: https://drive.google.com/file/d/0ByScwSCTIaUGUkZoTXhoTFhjU3c/edit?usp=sharing
Many thanks

Could you post a screenshot of the physics tab, too (last tab on the right)? I can't download the blendfile where I am, but I think those physics settings are the only other thing I'd need to see.

@Matt Sure Here: http://pbrd.co/1bxDXD4

Hmmm...that's not what I expected to see... I don't think any of those settings should be causing any problems. You might also check the physics settings on the particles. IIRC, there's a way to specify whether or not the particles interact with collision meshes. Another thing to check is that you are using enough subframes (usually not necessary, but for fast motion, it can help to calculate 2-3 subframes).

I tried your blend in 2.69, and the cube is blocking the particles for me as you expected, even with 0 subframes for the particles.  Is it possible your particles are "Baked" and you need to free them (in your particle system in the Cache settings)?

@PhillipKinkade Sorry, I couldn't answer yesterday, but thanks for your suggestion! I'll have a look at the answer below.

This reproducable as Phillip Kinkade mentioned, when the particle system animation was baked without the collision object, later adding wouldn't make them collide.

Free Bake
Position your collision object
Bake

After the three steps above no more particles will go through the cube:


text:
Why are blender console and info window values different for the same object?
I tried to find out what armature.bones.head and -.head_local stand for.
So I first get the values of them first from upperArm.R

C.object.data.bones['upperArm.R'].head
      Vector((-0.14598365128040314, -0.014478057622909546, -0.002403122605755925))
C.object.data.bones['upperArm.R'].head_local
      Vector((-0.1459999978542328, 0.0010000000474974513, 0.43689292669296265))

I open the property panel, the head position is
-0.146,0.001,0.437
which is the same as the head_local.
All right.  But when I click the Z property, the infor window showed that
bpy.context.object.data.head[2] = 0.437
So who tell the truth? 0.437 comes from head or head_local. Two part show two different answers.
Can anyone help in this?

You'll notice that the property window only shows three decimals of precision.
If you round 0.43689292669296265 to three decimal places, you get 0.437.
They're both accurate, but one is more precise than the other. If I were you, I'd choose the one that's more precise. Note that you can put the very long number into the field in the property window, but it'll get rounded.
In short, always choose the referenced value, not the displayed value. The interface is getting a number from somewhere, and then formatting it for display to the user. Instead of using a value that's being modified to fit nicely in a field, you should reference the same value that the interface is referencing.

source: Stack Exchange

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

sort: votes


text:
Hair does not show up in final render
When I render the hair only the root shows up and not the hair. Please help and thank you for your time
Here's the .blend

The problem is you've set the Shape parameter value to 1 in the Cycles Hair Settings. According to the Blender wiki:

A shape parameter that controls the transition in thickness between the root and tip. -1 gives a constant thickness equal to the root, 0 gives a linear transition and 1 gives an instantaneous transition to the tip radius.

What happens when you set that value to 1 is it makes the thickness of the hair strand the same as the tip radius, which in this case is 0. That's why it didn't show up in the render.
Change the Shape parameter value to 0 and it'll work.

You could try Layer Properties -> Filter and make sure Hair is enabled if you have any other problems with hair showing up in cycles.

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

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


text:
How to make a sub-menu with Python?
I want to make something like this:

I want some options to appear in a submenu.
Here is my script which creates only single menu:
bl_info = {
        "name": "Draguu",
        "category": "3D View",
        "author": "Pratik Solanki"
        }

import bpy

class buttons(bpy.types.Menu):
    bl_label = 'my materials'
    bl_idname = 'view3d.mymenu'

    def draw(self, context):
        layout = self.layout

        layout.operator('grass.button')
        layout.operator('fall.button')
        layout.operator('skin.button')
        layout.operator('rock.button')
        layout.operator('sky.button', icon = 'WORLD')
        layout.operator('setrender.button')
        layout.operator('setsub.button')
        layout.operator('resub.button')
        layout.operator('mod.button')

#grass button

class hello2(bpy.types.Operator):
    bl_idname = 'grass.button'
    bl_label = 'grass mat'

#on button press event.....................................................

    def execute(self, context):

# Material Properties....................................................
        mato = bpy.data.materials.new('grass')

        if mato!= None:

            mato.preview_render_type = 'HAIR'
            mato.diffuse_color = (0.2,0.8,0.04)
            mato.specular_intensity = 0.1
            mato.specular_hardness = 20
            mato.ambient = 0
            mato.use_transparency = 0
            mato.alpha = 0.01
            mato.strand.root_size = 1.5
            mato.strand.tip_size = 0.25

# adding blend texture  ......................................................

            gtex = bpy.data.textures.new('grass blend', type = 'BLEND')
            gtex.use_color_ramp = 1

            ramp = gtex.color_ramp

            ramp.elements.new(0.05)
            ramp.elements.new(0.18)
            ramp.elements.new(0.4)
            ramp.elements.new(0.69)

            ramp.elements[0].color = (0,0,0,0.2)
            ramp.elements[1].color = (0.02,0.007,0.001,1)
            ramp.elements[2].color = (0.01,0.05,0,1)
            ramp.elements[3].color = (0.02,0.1,0,1)
            ramp.elements[4].color = (0.07,0.3,0,0.8)
            ramp.elements[5].color = (0.2,0.8,0,0.5)
            ramp.elements[5].position = (0.89)

            gtex.progression = 'LINEAR'

 # adding material slot to assign texture ....................................

            mtex = mato.texture_slots.add()
            mtex.texture = gtex
            mtex.texture_coords = 'STRAND'
            mtex.use_map_color_diffuse = True
            mtex.use_map_alpha = True
            mtex.alpha_factor = 0

            ing = 'FLAT'
# adding cloud material for variation

            #defining texture type and assigning to variable
            ctex = bpy.data.textures.new('grass variation', type = 'CLOUDS')
            mtex2 = mato.texture_slots.add()  # adding texture slot
            mtex2.texture = ctex              # assigning to slot

            ctex.use_color_ramp = 1
            ctex.color_ramp.elements[0].position = 0.28
            ctex.color_ramp.elements[0].color = (0,0.06,0,1)
            ctex.color_ramp.elements[1].color = (0,0.3,0,1)
            ctex.noise_scale = 0.02
            mtex2.texture_coords = 'UV'
            mtex2.blend_type = 'OVERLAY'
            mtex2.diffuse_color_factor = 0.5

# applying material to an object ..............................

            bpy.context.object.data.materials.append(mato)

#closing on press event   ....................................

        return{"FINISHED"}
#-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

# fall off button ............................................

class hello3(bpy.types.Operator):
    bl_idname = 'fall.button'
    bl_label = 'add falloff'

    @classmethod
    def poll(self, context):
        if context.object and context.object.type == 'MESH':
            return len(context.object.data.materials)

    def execute(self, context):

        fall = context.object.active_material

        if fall!= None:

            ftex = bpy.data.textures.new('falltex', type = 'BLEND')
            fslot = fall.texture_slots.add()
            ramp = ftex.color_ramp
            fslot.texture = ftex

            ftex.progression = 'SPHERICAL'

            ftex.use_color_ramp = 1
            ftex.color_ramp.elements[1].position = 0.51
            fslot.texture_coords = 'NORMAL'
            fslot.mapping_x = 'NONE'
            fslot.mapping_y = 'NONE'
            fslot.diffuse_color_factor = 0.6
            fslot.blend_type = 'ADD'
            return{"FINISHED"}

#_______________________________________________________________________________-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

def register():
    bpy.utils.register_module(__name__)

    wm = bpy.context.window_manager
    kc = wm.keyconfigs.addon
    if kc:
        km = kc.keymaps.new(name='3D View', space_type='VIEW_3D')
        kmi = km.keymap_items.new('wm.call_menu', 'D', 'PRESS', ctrl = True, shift = True)
        kmi.properties.name = "view3d.mymenu"

def unregister():
    bpy.utils.unregister_module(__name__)

    wm = bpy.context.window_manager
    kc = wm.keyconfigs.addon
    if kc:
        km = kc.keymaps['3D View']
        for kmi in km.keymap_items:
            if kmi.idname == 'wm.call_menu':
                if kmi.properties.name == "view3d.mymenu":
                    km.keymap_items.remove(kmi)
                    break

if __name__ == "__main__":
    register()

Can anybody tell me how to make these buttons appear in a submenu?

Please don't links to the script if it can be helped, best include a small example in the question.

All you need to do is to define 2 menu's, then reference one from another with layout.menu
import bpy

class ButtonsSub(bpy.types.Menu):
    bl_label = 'my materials'
    bl_idname = 'view3d.mymenu_submenu'

    def draw(self, context):
        layout = self.layout

        layout.label("This is a submenu")
        layout.operator("render.render")

class ButtonsMain(bpy.types.Menu):
    bl_label = 'my materials'
    bl_idname = 'view3d.mymenu'

    def draw(self, context):
        layout = self.layout

        layout.label("This is a main menu")
        layout.menu(ButtonsSub.bl_idname)
        layout.operator("render.render")

def register():
    bpy.utils.register_module(__name__)

def unregister():
    bpy.utils.unregister_module(__name__)

if __name__ == "__main__":
    register()

    # call menu now! (you wouldn't normally do this, just to test)
    bpy.ops.wm.call_menu(name=ButtonsMain.bl_idname)


text:
How to smooth animation?
Why is my animation shaking so much? It's not smooth. When he is in the air in one frame he falls down suddenly. His head and upper body shakes. I hope you understand what i mean, you can see my animation here: http://screencast-o-matic.com/watch/cIlo6wnV5D

It's not that bad I think? But if you want to see motion over time, use the graph editor. Here you can see how transformation happens over time. The more vertical the curve is, the more rapidly the change are. If the curve delta (change over time) differs, the movement may appear jerky.
In the screenshot below I have circles a jerky translation.


text:
Why is the Z very noisy around out of focus objects?
I am doing a render of a tutorial I finished, and when I go compositing it I get a weird jitter on a defocused object. The tutorial had this too (at 1:04:00), but I wonder if it is possible to remove it. I tried adding a blur/defocus node but it ended messing up with the map value.
This is the jitter I'm talking about:

And this is my node setup:

Just raise your samples.

I think they were at 24 when rendering. The rest of the scene looks fine, it's jittered only when I try to apply the map value.

Try raising them and see what happens...

Also, are you using render DOF?

Are you using cycles or BI? Could you link to the tutorial in question?

try increasing your F-Stop value

I've made an imgur album with some attempts. I'm using a simple scene to make rendering faster. @GiantCowFilms yes, I tried both the number distance and the object focus, both have the same problem. And raising the samples didn't worked, as you can see in the album.

@gandalf3 I'm using cycles, but even in BI the edges are a bit jittered without defocus (couldn't get defocus to work). Tutorial Link You can see the jitter at about 1:04:00. It isn't much noticeable in his final render because he made the fog a bit darker.

@G.Rassovsky I tried at max f/stop, it improved things a bit but the edges were still a bit jittered. But at max f/stop I'd lose the defocus. By the way, thanks for trying to help guys.

Usually it's a matter of balancing the F-stop and shutter speed, in a camera, in order to get the right picture. I am not sure what that equivalent would be but I would suggest playing with the distance of focus too, along with the F-stop. (putting it to max is way too much, it should be more subtle than that).

It seems the Z always gets only one sample, so it's always noisy around defocused objects regardless of the number of scene samples. However using the mist pass (which was added since that tutorial was made) instead of the Z gives a better result:

To define the distance/thickness of the mist, enable the mist display in the camera settings so that you can see a visualization in the 3D view:

Then adjust the start and depth of the mist in world settings:

Yes, this is exactly what I wanted! Thanks a lot!


text:
What's the fastest way to select every other vertex of an edge ring?
What's the fastest way, without using Python, to select every other vertex of an edge ring with an even number of verts?

In edit mode with entire edge ring selected:
Select> Checker Deselect
This should deselect every other vertex.
You can then use the 'offset' value in the toolshelf if you want the other vertices in the edge ring selected.
No Offset:

Offset by 1:

Note: This works in edge and face mode too, deselecting alternate edges or faces to get a checkerboard selection.

Oh boy, I'm humbled. It even takes the active vertex into account as a starting point. Thank you

I can't find the offset.

The offset option as well as the nth option (so you can select every 3rd vertex or 6th vertex...) is available in the operator options - either F6 or at the bottom of the toolbar panel T

I would like to comment is that Blender is absolutely brilliant.

If the topology is well-formed for it, which is surprisingly often,  then CtrlShiftNumpad + 'Select Next Active' will select a sequence of vertices, edges, or faces, in a pattern established by the last 2 selections:

If you switch off 'Select' on AltH Reveal Hidden, and make use of 'Header > Select > Select Loops > Edge Loops'  and/or  'Header > Select > Select Loops > Edge Rings', then by hiding and unhiding, you can find your way to a wide range of useful patterns that are not always available through 'Checker Deselect' :


text:
What does "users" means in term of datablocks?
I found that there is a "fake user" button (with a F icon) on object data tab in properties editor. What is the exact meaning of users and its usage?

Blender organizes its data in datablocks. These are chunks of data (bits and bytes) that belong together, like all the settings of a material or the verts and faces of a mesh. When you give a mesh a material, this data isn't merged, but linked. You tell Blender: whenever you use mesh X, display it with material Y.
When a material is linked to something, it has a user. Another datablock that uses this material. When a material is used by a lot of objects or meshes, it has many users, displayed by the number to the right of it's name.
That way you can have a thousand objects all using the same mesh, which takes up less memory and enables you to edit one mesh and affect all linked objects simultaneously.
Fake users are a way to keep a material alive even if no object or mesh uses this material. If a datablock has no users, it will not be saved when you save the file in order to decrease file size. Think of it as some kind of garbage collection. However, the fake user takes care of this problem.
To illustrate that, I have resurrected Blender 2.28 because it has a view called OOPS schematic that shows the linking very well. Below, you have four objects all linking to one Suzanne mesh. I'm in the edit mode of the upper left Suzie and mess with her ears. Since all four objects use the same mesh, all objects are changed simultaneously.
One easily overlooked feature is copying lamps with altD. All the lamps then share the same data. This way you can change every lamp's brightness in one go. Think of a row of street lamps.

WOW - all the way back to 2.28 for that. You do know that 2.49 still has the OOPS display? I wouldn't be surprised if you have a copy of 2.49 installed but 2.28? ;-)

@sambler It just happened to be the first classic I found on my machine. In a way I felt much more at home with 2.28 than today. I still wonder if the simplicity could be preserved while handling the huge amount of buttons. And I sometimes pull the info window to get to the user preferences. Muscle memory.

Users refer to parts of blender that are using that item. For example an image could be used as a reference image and also used in a texture so it's users would be listed as 2 because two parts of blender are using it.
The fake user option is there to prevent blender from removing that data from the blend file when the file is closed. When closing, Blender will look through parts of the blend file and if something isn't being used (it has zero users) it will be removed from the blend file. Pressing 'F' ensures that blender will keep the data even if it isn't being used, because you might want to use the data at a later date.
In terms of 'Object Data', this means that the vertices that make up the object, the shape keys, UV maps and vertex colours will be shared between 2 different objects. This can be used to create instances of an object so that editing one will update the other because they are linked.
Editing a cube that was sharing object data would update the other cube at the same time regardless of their position, scale or rotation in the scene.

Users means the number of datablocks that have refernces to the datablock that shows the number of references. To avoid that e.g. that a material will be removed when the .blend file is saved, a fake user can be added, otherwise a non referenced material would be discarded.
See also the docs on Users and Fake User


text:
Snap to mesh issues with Z and X axis constraints
I have two meshes that I've joined to a single object.  I'm attempting to use the snap to mesh feature for each of the 6 vertices on the face of mesh 1 to snap them to different faces/edges on mesh 2.
I select the vertex I want to move, press Y to constrain movement to only the Y-axis, and then it slides smoothly along the Y, not snapping to the face.  Is this behavior intentional?  Is there a better way to do what I'm doing while maintaining precision?
I'm using Blender 2.6.

IIRC There is a bug in 2.69 (now fixed in the development versions) which makes face snapping not work in orthographic view. Try it in perspective view if you haven't already (it's hard to tell from your screenshots)

I was in ortho, but switching to persp doesn't seem to fix the issue.

Hm.. What happens if you try it in a later version (2.69 is the latest) or a development version? (everything looks right, so I'm inclined to think it's a bug)

Still doesn't seem to be fixed in latest snapshot on master branch.  Thanks for the responses, though.

Perhaps you could upload a .blend where this is happening? It works fine for me using the same settings. Here is a file where it's working.

Here's the file from my screenshots.  Moving the selected vertex to the left, constrained to only Y movement, until it snaps to the face it's lined up with on that axis.  Other snap to mesh options seem to work fine, but it seems to just not attempt to snap to anything as soon as I constrain it to Y.  A friend made a nearly identical set of meshes from scratch and found the same behavior.  Maybe it refuses because of it causing the meshes to intersect for some reason?  Maybe it's related to the normals of the faces somehow?  I have no idea at this point.

Very odd... You could try posting a bug report with that file.

I tried playing with both files as well. Couldn't figure out why Fen's file doesn't work.

There is another way to solve this (that may work), using the shrinkwrap modifier. Do this before joining the objects.

Create a vertex group with the vertices you want to snap.
Add a shrinkwrap modifier.
Set your vertex group as the one affected.
Set mode to "Project".
Select the axis to project along.
Tick both positive and negative (maybe you need to do this).

Like this:


text:
Bones not moving in pose mode?
When ever I try to move or rotate a bone in pose mode, nothing happens. The bone stays frozen, not moving to any axes, no matter what bone I chose..
I tried rigify ready to use mesh but had the same issue.

Is the Armature not in "Rest position" ? You can check that in properties > Armature tab > section "Skeleton". If so, just switch to "Pose position" and retry.

nop. it's in pose position. if it would be in rest, there would be errors.

I had this problem and just discovered the "manipulate center points" option was enabled (shortcut: alt ,). It's the button to the right of the pivot center pulldown in the 3D viewport menu. Disabling it solved my problem.

Try disabling Manipulate center points.
Here's a screenshot of the option:

This worked for me, thanks! The location of the option has move per this post
https://blender.stackexchange.com/questions/154340/where-is-the-manipulate-centers-only-button-in-blender-2-8


text:
Select multiple overlapping islands in UV Editor?
I want to select multiple overlapping islands all at once in UV Editing mode. 3dsmax can do this by clicking and dragging a window around my element, but I couldn't find a comparable function in Blender. Not being able to select in UV Editing by clicking and dragging a window is a huge missing feature, or I am not sure how to find it :/
See below:

I want to select the islands corresponding to the fan in the editor, which are around 12. I got them to overlap, but cannot select all of them at once.

You can use Box select, which is activated with B:

You can also use C for Circle Select and CtrlLMB for Lasso Select.
For more on selection tools in the UV editor, see the wiki.

Ah, thats it! Couldn't have figured it out on my own! Thanks!

@SyedImran Do you mind to pick this one as the answer by clicking on the √ icon on the left?


text:
Why is my render all blurry and pixelated?
When I render out my blender animation project into a video file, it blurs, pixelates, and glitches in some spots. Why is this happening?
Is it because I'm using Ogg Theora with Vorbis as the format?
Example:

Blend file
Output video
The input is 1080p video composited with an animation. Don't know why it's pixelating so much. Is it compression?

It looks to me like compression artifacts. To test this, try rendering a single frame (F12) and comparing it to the video.

Your video output looks so bad because of the low quality setting specified in the render output.
First Things first:
You should never render out your 3d renders as movie files, NEVER! The reasons for this are:

If you mess up the quality settings you will have to re-render from the beginning
If you computer crashes halfway through the rendering all render will be lost and you will have to start over

The only time when you would want to render out a movie in blender is when you have an ready rendered animation as an image sequence and you want to convert it to a single movie.
The proper way:

Render out your animation as an image sequence. The output files should be a very high quality image which is why I would use either: png, tga, exr or whatever will yield a good looking image
In the blender Video Editor load the image sequence as an image sequence.
Now render out as a movie

Back to the actual question. You need to increase your render settings. Here are the important parameters you need to consider increasing:

Format

Bitrate: The target amount of data per second in your video file
GOP: The number of key frames for the color palette. A value of 10 means that during those 10 frames all are drawing frames based on the same 256 colors. If your scene is changing color during this time the quality will suffer.

Rate

Minimum: The lowest the Bitrate can be per second
Maximum: The highest the Bitrate can be per second

I think in your case the following settings would yield satisfactory results

If I were to render as a sequence of pngs, I could possibly ditch the compositor, render them with an alpha background, and then put them in the video sequencer with alpha over right?

I assume I might also want to drop the GOP down to 2 because there's a lot of flashing and color change in the original video. I'll try this out when I get home.

@Vader: the explanation of GOP. Where did you get the information on the use of palettes for keyframing and a 256 colour limit? Especially in regard to the theora codec. Thanks in advance.

well it's 8 bit, so that means 256 color per channel. I am not sure about the ogg format. I am just taking a swing.

I see. So it´s just an arbitrary example. Was just rereading the spec and scratching my head :-).

fell free to edit the number so that is correct.


text:
Blender 3D Printing hollow model
I am trying to export an .STL I can actually 3D print with Blender. I have run through all the tutorials, but my model won't print correctly. I believe the problem would be solved if I could just select the outer shell of the model.
I want to extract everything that is outside (the shell) and delete the inner core. After that I would like to close holes and simplify the model to print. How can I achieve this? Thank you for your help.

If the outer part is not connected to the inner part, then you can select it by pressing L while hovering over it with the mouse.

Unfortunatley it is connect and rather complex as well. Therefore I am looking for a way to just get the outer shell (imagine a 3D skull without the inner complex part). Thanks for your help.

You could try addidng another mesh as hull and use several subsequent subsurf and shrinkwrap modifier to build a manifold hull.

Select the vertices around the part joining the inside and outside and hide them H, then you can use L to select the outer shell and hide it leaving the inside to edit or delete.

You could also try creating a convex hull, by selecting everything in edit mode and typing Space > convex hull.

If there is only one connection area between the inner and the outer shell:

select a ring of edges/vertices around this connection
press Ctrl + E and then click on "Select Loop Inner-Region".
this will either select the inner shell or the outer shell. If it's the wrong one, press Ctrl + I (invert the selection)

If there are several, but not outrageously many holes between inner and outer shell:

mark them as seams (Ctrl + E -> "Mark Seam")
then press U -> Unwrap with everything selected to unwrap the model
go into UV/Image Editor, select one of the vertices and press L to select one of the two shells, pull that away far enough so that it becomes easy to box-select
Press "Keep UV and Edit mode mesh selection in sync"

select one of the islands, it will select the corresponding mesh, too.

If there are outrageously many holes between inner and outer shell:
I don't know. You could try box-selecting the outside with "limit selection to visible" active, but you'll get a few inside faces, too. Some of them may disapper if you "Select less" a few times, and then not re-appear if you "Select more" the same amount of times.
You could try selecting the outer shell in Wireframe viewport shading just because it's further outside at the edge, rotating around your model.

In Edit Mode, hit C and select everything you want to keep. Select inverse and H for Hide. This did the job for me.

If I understand you correctly, Solidify modifier is what you are looking for. To test how it works try this:

create a cube
in the bottom left panel select Modifiers (the wrench icon)
click add modifier, select Solidify (Generate colomn; when doing this, the cube should be selected), select params (thickness etc), click apply
to check out how it worked, create another cube (preferrably bigger one), move it so that it intersects the first one, but doesn't cover it fully
select the first cube, add Boolean modifier in the same fashion, use Difference  (the left dropdown) with the second cube as Object (the right dropdown), Apply
move the second cube away to see what is left from the first one. If you have done everything correctly, you'll see that the first cube (remainder) is hollow

In fact, this is possible for other objects, too (use the last 3 steps to check out how it works).

In fact, you can find this at http://blender.stackexchange.com/questions/35415/why-is-blender-so-popular-for-3d-printing/35441#35441 if you search by "print hollow"; there's some other useful stuff, too

One thing that I can also suggest is to use the free plugin from 3YOURMIND (https://www.3yourmind.com/3d-print-add-on-blender) to export the model directly from Blender to their online platform. They then do free analyzation of the file, fix many of the most common formatting errors in the .stl for you and guarantee the printability of the final data in a variety of materials.
Several of the problems the other users mentioned (filling holes and gaps, creating clean connection points, etc) are completed as part of the analyzation process. It is definitely worth a try if it isn't working as a direct export from Blender.


text:
Play movie, image, or image sequence at specified time?
I have a live-action shot of someone holding a gun and fake-shooting. I want to add muzzle flashes with Blender's compositor, so I grab my muzzle flash stock image to overlay onto the shot. How can I make the flash appear at selected points in my shot?
So far the only thing I've found that seems close to this functionality is the Offset option on the Image node when an image sequence is selected, but this just skips frames, it doesn't place the sequence in time.
What I really want to do is decide when a Movie, Image or Image Sequence plays in my composition. How can I do this?

Image sequence
You can specify the frame one which the image sequence starts with the Start frame property of the the image node:

Video file
I don't know of a way to do this with a video file in the compositor (there is no start frame option on the  movie clip node).
Note that this is a very trivial matter in the VSE (Video Sequence Editor) for still images, image sequences and video files:

The movie clip editor stores a frame start and offset value in the clip properties. However it is per scene value meaning you cannot use multiple instances with various off sets.  A movie file can also be loaded in the image node so that you can access the frame and offset values but you can't use proxies or timecode.


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Can I restrict viewport render to inside the camera
Is it possible to enable viewport rendering, but when in camera mode, restrict it to only inside the camera?
My current workaround is to hit Ctrl+B for render boarders, and select as much of my camera as possible.

Yes, albeit through a rather cumbersome process.

Select a border larger than the camera (this will set the border how you want, but then disable it)
Re-enable render border

I actually wrote a patch to expedite this process by removing the "auto disable" behavior. However opinion was divided on weather or not removing the auto disabling was an improvement (IMO it is), so the patch was not accepted (yet!)..
If you have any feedback or ideas how to implement a faster, more convenient workflow, by all means leave a comment on the revision page :)

I agree that your patch would have been the right way to go!

It seems that things working now. I guess the issue has been fixed (at least in the current v2.78).

Pablo Vazquez has created an addon called the Amaranth Toolset which (among a ton of other useful features) adds a way to do exactly what you are looking for.
Once the addon is installed just go into camera view and hit W > camera as render border.

I know I came a bit late to this question but in newer versions of Blender, I'm currently on 2.78c, there is a check box under the dimensions tab that allows you to do this. The checkbox is labelled Border

@cegaton Whoops my bad. I will fix the image when I next switch computer on. Thanks for pointing that out :)

Not sure if this is a different way to do it or they changed it in Blender 3 but I achieved this by toggling "Render Region" on:


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What is this dashed box and how can I turn it off?
I was just getting back into using Blender a few days ago and I must have hit a couple of buttons. But now I cannot get these dashed lines to go away. Does anybody know how I can make them go away?

It looks like you pressed ShiftT which enables texture space display and translates/grabs it.
You can disable Texture space display in Properties > Object > Display:

In case you accidentally translated it, you may want to set it back to 0,0,0 in Properties > Object data > Texture space and re-enable Auto texture space:

I recently disabled the keyboard shortcut for this feature in the user preferences, now it no longer pesters me when I mistakenly press that shortcut when I am trying to Triangulate(Ctrl-t).


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Real Time Reflections in the BGE
I'm trying to achieve real time reflections in the game engine, possibly using the render to texture module if needed, but am not sure exactly how to go about it. Faking reflections using cube maps, etc, are simple enough, but that doesn't achieve a true reflection.
I want to be able to see a true reflection of my character if he/she moves in front of the mirror.
If you're still confused, take a look at a real mirror. That is what I want to simulate.
Any tips are appreciated.

Are you trying to achieve this ?
https://www.youtube.com/watch?v=RgSWZV4hvNo or the following
https://www.youtube.com/watch?v=3JUYFGkmE1Y
Follow the link attached to the youtube video and you will find discussion on the matter there, I am afraid there are very few who write about or have alot to share on this topic, as blender BGE is very much in development for 2.8.

You will wanna watch post by this guy martins upitis on youtube and on blenderartist.org

@hawkenfox Thanks, this may be of some use to me. Martins Upitis is definitely a good artist to keep an eye on. Do you know if "bge.texture.ImageMirror" still works in the latest builds? I have never used it before, as I can only find older forums referring to it.

Unfortunately I havent have the time to dig too deep into the code. Mostly of what I do is to cut and paste and understand on the surface of what they do. BGE is getting alot of rebuilding this year, I am holding the horses until they announce a clearer picture of what the future BGE will be like in blender before learning things that will eventually get scraped.

I did read up a dev blog on the BGE development, it seems that they need a real major overhaul. It has become a real pain to develop BGE due to poor code housekeeping according to one of the dev. So will see what happens .... soon enough.

See: http://blender.stackexchange.com/questions/2741/how-can-i-create-a-mirror-material-for-the-game-engine

Oh, cool! Thanks @stacker for reminding me of that link. Whenever I came upon that forum I always thought the Image Mirror was for older versions of blender, but apparently it still works in 2.74. Thanks for the redirection.

Tutorials for blender 3d has an excellent tutorial over here
It uses renderToTexture with a mirrored UV map and a camera facing out of the mirror.
One thing to keep in mind is that this requires the scene to be rendered twice: once from the main camera, once from the mirror camera. As such, it can increase processor load quite a lot.


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BGE Object List within a specified distance
In a script that I'm writing I'm trying to create a list of all the objects within a specific distance of the player which have a certain property assigned to them, but I can't figure out how to get the script to search within that specified distance instead of across the entire scene.
For instance, to create a list of all the objects within a scene that contain a specific variable, I can use the code:
object_list = [ob for ob in scene.objects if ob.get("property_name")]

I have several hundred objects that contain this property, but I only want the objects that are within a specific distance from the player to be put into the list.
Now here's the dilemna: I need to create the list every frame, and I know it's possible to do what I want by scanning for every object in the scene with the property, but with several hundred (potentially thousands) of objects in the scene using this method becomes way too resource intensive.
So my question to you; Is it possible to only scan the objects within a specific distance from the player, for any object with the specified property?
To clarify, for ob in scene.objects scans the entire scene for a specific object. Is it possible to do exactly the same, but only for a small section of the scene (within a distance from the player)?

Looping over all objects is not that inefficient and often used when the near sensor is too heavy.

How is scanning through thousands of objects to create a list of several hundred objects every frame not inefficient?

You can do it this way.

Add near sensor.

Get the list of hit objects.

Script if near sensor look for specific property name
from bge import logic

nearSen = logic.getCurrentController().sensors['Near']
list = nearSen.hitObjectList

or if near sensor not look for specific property name
list = [obj for obj in nearSen.hitObjectList if nearSen.positive and 'property' in obj.getPropertyNames()]

Edit
The objects need to be set to actor so the sensor can detect them.

Download the blend to see how it works.

KX_NearSensor
KX_TouchSensor

I tried what you've explained above, but everywhere that I tried to implement the code it gave me either a "KX_NearSensor object is not iterable" error, a "KX_PythonSeq object is not callable" error, or it printed an empty list, even though there should have been around 30 objects in the list. Why can't I get the names of the objects hit by the near sensor?

Well you are doing something wrong. Make the objects actors so they can be detected by the sensor, Make Sure the distance is correct and check the blend file i upload in the answer.

I sorted the problem, as you said they have to be actors, but also I had the distance set to 0, which is why the script kept printing a Null result.

I think I can help you a bit.
To make the scanning more efficient you have some options:
Reduce the number of frames with scan
You need to check every time when at least one of your criteria changes:

object with property gets added
object with property gets removed
object gets property added
object gets property removed
object with property enters scan distance
object with property leaves scan distance

I guess you know when objects are added (1.) or removed (2.). This should not happen that often. After that you need a new scan.
I think 3. and 4. can be excluded as long as you do not manipulate the properties via Python. But you should know when that happens. So you need to scan after that.
From the information you provided I can't exclude any object to run into 6. and 7. any time. You might isolate objects that are not moving (as they do not change distance) as long as the player is not moving. A moving player needs a scan after each single step.
Reduce the number of scanned objects
Unless you can make some assumptions, there is nothing to isolate candidates.
This depends on your  specific situation (e.g what objects can move what objects can't move).
In your example you can create a list of candidates via property containment (as in your code).
I assume you have much less objects with the property then without.
When you cache the candidates:
candidates = [object for object in scene.objects if "property_name" in object]
owner["candidates"] = candidates

You can iterate over the them at a later time:
candidates = owner["candidates"]
# do distance check with candidates

You update the list when on the events from above (1. - 4.).
Efficiency
When you use both methods (reducing scans + reducing number of candidates) you should reduce the processing time quite a lot.
Lets do some estimates:
Worst case

all objects (5000) are candidates
the player moves constantly

-> you are where you are now, scan all objects at each single frame
Best case

there is no candidate

-> nothing to do
-> a little overhead to check there is nothing to do
Average Case
This is hard to determine as it depends on your situation. So this is just a wild guess:

100 of 5000 objects have the property
10 of the candidates are constantly moving
the player moves frequently (~50% of the time)
candidates are added/removed every 10 seconds

You update the candidates every 10 seconds (iteration over 5000).
You scan 100 candidates all the time (iteration over 100).
Conclusion
You can get more efficiency

when no candidate is moving (as you need to check only when the player moves).
when you can isolate candidates even further (e.g. exclude a complete group of candidates).

I know this is still a bit vague, but it should provide you an idea.

Thanks, this will be useful for refining the script further, highly appreciated.

I would cycle through all the object in the scene with a for loop. Then check each with a if statement which checks if they are within a certain distance. If it passes that add it to the list.

Yes, that's what I'm currently doing, which I tried to explain in my question (but obviously I wasn't clear enough), but this method is waay too resource intensive... I want to only cycle through all the objects in the scene within the specified distance. Does that make sense?

@christai Ok, sorry I didn't understand that. There might be another way to do it but I don't know of it.


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Importing trajectories to create an animation
I am using blender to model a robot in my own robot simulator. To create better videos of my simulation results, I would like to log e.g. the positions and orientations of all segments to a log file and import that into blender to create an animation. Is there a canonical way to write such log files, or is there even a python module already out there?

There are several easy ways to exchange data, common formats are .csv or .json and both can be written and read easily.
What you might end up doing is have csv file like this:
timestamp,p1x,p1y,p1z,p2x,p2y,p2z,p3x,p3y,p3z....etc
0:000,x,y,z,x,y,z,x,y,z....
0:020,x,y,z,x,y,z,x,y,z....
0:030,x,y,z,x,y,z,x,y,z....

The timestamp could be as fine grained as you want, or 24 frames per second. Exactly how you turn the information into an animation is entirely up to you and can also be entirely scripted.
Here's a movement.csv, which uses a frame number instead of the timestamp, simply because it makes the example more convenient.
To start off you might want to simply key-frame some empties. Let's say we have 48 lines of data for 3 points in space, and they describe these arcs (though can be any complex path)

import csv
import os
import bpy

# add 3 empties programatically to be certain it works as a demo
mt1 = bpy.data.objects.new('mt1', None)
mt2 = bpy.data.objects.new('mt2', None)
mt3 = bpy.data.objects.new('mt3', None)
empties = [mt1, mt2, mt3]
for m in empties:
    bpy.context.scene.objects.link(m)

filename = 'movement.csv'
directory = '/home/zeffii/Desktop'  # <-- if you have linux or osx
# directory = r'c:\some\directory'  # <-- if windows, the r is important
# directory = 'c:/some/directory'  # <-- if windows (alternative)

fullpath = os.path.join(directory, filename)

with open(fullpath, 'r', newline='') as csvfile:
    ofile = csv.reader(csvfile, delimiter=',')
    next(ofile) # <-- skip the x,y,z header

    for line in ofile:
        f, *pts = line

        # these things are still strings (that's how they get stored in the file)
        # here we recast them to integer and floats
        frame_num = int(f)
        fpts = [float(p) for p in pts]
        coordinates = [fpts[0:3], fpts[3:6], fpts[6:9]]

        bpy.context.scene.frame_set(frame_num)
        for ob, position in zip(empties, coordinates):
            ob.location = position
            ob.keyframe_insert(data_path="location", index=-1)


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Folding a cube (animation)
I'm trying to fold a cube with an animation. I've tried inverse kinetics with no luck. Here are some images that explain what I'm trying to do. I'm trying to make this so that

when the upper bone is pushed down, the box is folded to the ground.
when the upper bone is pulled up, it unfolds the box.

"when pushed bottom or top the box is folded to the ground or if up makes the box." could you further explain that?

The bone in the top of the box, is the main bone. When i push the bone down, its suposed to make the other bones "fold" in order to be like the first example in the second image. If u pull the bone up in the z axis, its suposed to make a box

ah, thankyou. a bit hard to interpret there... :-D

No problema, u know how to fix that:s?

I think you'll have to use drivers on the box's bones, to drive them according to the main (top) bone's local position.

one possible way is to use :

use the Transformation constraint to convert translation to rotation from control bone to lower bones
use the copy rotation constraint to make the upper bone rotate in reverse to the lower bone

The Transformation constraint to the lower bone with this settings :

the Copy rotation constraint on the upper bone :

there's only one plane ( with middle edge) and have an array modifier controlled by an empty ( see the .blend file )

Could u make some explanations how to reach that point? im have almost zero experience in bone managment

Im having some problems reproducing the same animation...

@Chebhou, care to elaborate? you have the right answer, but it's unclear to newbies.

Sorry i was in a hurry , I'll add details now

@Warianos added the example file you can download

@Warianos , see the Z-->Y this what's missing for you, on the other two bones put   Z--->X

Ok now i almost got it, the problem now is that when at the x axis the bone  when inverted automatically inverts 180º and stays on top of the lower bone plane, like the image shows.

@Chebhou Could u help me with this bug? :) evertything else is already well done

The way Chebhou showed is rather simple:
for each of the 8 bones conected to the box, ad a transform-constraint(constraint-tab in the properties-panel)
use location of the middlebone as input and the rotation on x or y as output
or try this:
parent 4 bones to the top one, each placed at the top of a wall.
for each wall: place the mid a bit outside of the box and add an ik-constraint to the upper bone;
with chainlength=2 and tail=True, the targetbone being the bone placed on top of each wall.
the green one on the top is what you move, the big ones are to deform the walls, the small gray ones are the targets. they are children of the green one on the top. the green one has a limit-location-constraint(seen on the right), the yellow ones each have an ik-konstraint to the little gray ones, with a chainlength of 2

Im trying that but when i keep the offset of the 4upper bones to the top one. The bones get disconnected from the bottom ones.

Try to see the image i psoted there now

Since i dont understand how to work with constraints its really dificult, im trying but im not getting what i want

added a picture with my setup


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Link one object's property to another object's different property
New to Blender and just can't find a way to do this after a few days of googling. Any help much appreciated!
Is it possible to link the value of one object's animation Channel (for example the X-Location keyframe values) to another object (for example its Y location)
I don't want to copy the keyframes from one to the other. I would like the two to be dynamically linked so that moving the first object (adding keyframes) along the X axis automatically moves/adds keyframes to the second object along its Y axis.
Ideally I would also like to be able to alter the keyframe values being linked - so for example, Object1's X Location value when linked to Object2's Y Location value might be offset by 50 and inverted about the y-axis [ Object2_YPos = -(Object1_XPos+50) ]. Or the difference between Object1's X and Y co-ordinates would dictate the size of Object2 [ Object2_Scale = Object2_Scale*(Object1_YPos-Object1_XPos) ] that kind of thing.
For any of you who know Adobe AfterFX, I'm hoping to do something like linking with expressions:
https://helpx.adobe.com/after-effects/using/expression-basics.html#edit_an_expression_with_the_pick_whip
The big picture: I have complex data imported from a CSV file that includes a long list of three data points over time:
0,10,5,120
2,20,5,100
3,30,15,120
etc.

I've successfully imported this data and added it to my objects as keyframes. The first value is the frame number, then the different objects use each of the following values along different axis. So Object1 reads the CSV as:
frameNum,xLoc,yLoc,zLoc

and Object2 uses a slightly different import template:
frameNum,yLoc,xLoc,zLoc

The problem is that I end up with the same data in two different Actions which seems inefficient (I have a lot of data points; 1 per frame over 50000+ frames). Is it possible to have an Action that exists once in the Dope Sheet editor but which is used in different ways by different objects?
Update: As I typed this, 'Similar Questions' started to appearing which seem to suggest that the answer might be Drivers and/or animation nodes. All very new to me, so I'll go and investigate and post a reply to myself if I solve it. In the meanwhile, can anyone help point me in the right direction? I'll be very grateful for any help, advice and/or exemplar blender files as I find the docs a little cryptic at times :)

You want to use Drivers to drive one property by another, should be tons about it here or on the web.

Did you consider Constraints? http://www.blender.org/manual/rigging/constraints/introduction.html

First off, a big shoutout to TLousky who provided an equally valid answer. It just happens that I didn't go down that route...
I ended up installing Jacques Lucke's Animation Nodes add-on which provides a really nice way to do this visually within the Node editor.
Here are screenshots of my set-up - for the specific scenario I needed with 3 points on a graph (each offset by a set time) which are then projected in three dimensions.
First I offset my 'master' object (Sphere-X) which is animated to follow a 2D plot (graph). Sphere-X moves up and down on the Z-axis as it travels to the right on the X-axis. So in the first node tree below, the two slave objects  (Sphere-Y and Sphere-Z) follow the same X and Z transformations but each is offset by a set number of frames:

Then a fourth object (point_inCube) moves in 3 dimensions using the z co-ordinates of Sphere-X for its z location (that's the Copy Transforms node at the top) then Sphere-Y and Sphere-Z are each used to provide the other co-ordinate axis (but note the use of the Separate Vector nodes to swap from one axis to another):

I'll definitely investigate Drivers further (thanks again TLousky) but this solution works well for me as I'm from a music background and it reminds me a lot of setting up a patch on a modular synth!
ps.
This is the slightly different but related answer which helped me on my way towards using Animation Nodes instead of Drivers:
Change color with object rotation

This is a classic case for using drivers.
Drivers are a bit tricky to master BEFORE you know what they're good for, but your case describes a very good example for their use.
Drivers allow you to use one property (or several) to drive another. There are several types of drivers, one of which is an expression where you can use arithmetic operators and mathematical functions. This is really useful when you want to create offset / inverted / factored relationship between the driving and driven properties (which seems to be what you are looking for. For instance advance 2 units in object1.location.y for each unit of object2.location.x).
It will be rather cumbersome to explain how to create and manipulate drivers here in text, but there are quite a few excellent video tutorials (such as this one) that will get you quickly acquainted with drivers.
Once you've grasped how to add and manipulate drivers via the UI, you can automate the process via python.

This is really useful thank you. I particularly recommend that video to any blender noob like me.


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Animate different parts
I want to animate a lounger's legs in such way so they are folding together but I don't know how to make so only the legs are moving and not the rest of the lounger without separating the legs from the lounger.
I don't want to separate the legs because it looks weird when I subdivide the mesh.
Thanks in advance.
How I want them to fold:

When separate and subdivided (I don't want them to look like that):

Try to rig the mesh by creating an armature and positioning its parts adjacent to legs


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How can I batch render multiple blendfiles consecutively?
How can I batch render multiple blend files consecutively?
Are there different ways of doing this? If so, what would be an easy method?
I'm guessing there will be a command prompt method of some kind but I'm not very familiar with this. (although I'd love some pointers)
Basically what I'm looking for is a way to render a given blend file which executes the compositor nodes and saves the images connected to the file output node. When finished, I'd like the blend file to close and in it's turn open the next given blend file and so on and so on...
I'm not looking to render multiple scenes or render layers but actual blend files with it's predefined render settings.
Also, I'm aware that there are some render managers available but due to the lack of knowledge I'm not able to figure out how to set these up. (not really looking for a render manager here but an easy method to do batch rendering on the go)
I'm sure render managers have their advantages but I'm currently only looking to simplify some basic batch rendering (without having to get up in the middle of the night just to press a single button).

Possible duplicate: http://blender.stackexchange.com/questions/313/is-there-a-way-to-batch-render-multiple-scenes

Possible duplicate of Is there a way to batch render multiple scenes?

@JoshSilveous That question is specifically about multiple scenes and doesn't say much about multiple files.

You can look into the commercial addon Render+ it is a payed extension, but at $20 it is probably worth the price for the hassle it saves.

Do you want to render an animation or stills?

@pycoder Mostly stills.

@DuarteFarrajotaRamos Seems like a good addon, will look into this. But for my question specifically I just need an easy local batch render setup for multiple files.

I got sick of having to write the same command line scripts over and over to do this, so I wrote a little Python app to make things easier. Feel free to use it. http://blenderq.readthedocs.io/en/latest/index.html Basically it puts a UI on the command line renders, and provides some basic functionality like saving/loading groups of renders. I'm using it on my latest project to do about 10 still images per night.

in win10 you need to add blender path to environments as well for it to work: https://helpdeskgeek.com/how-to/fix-not-recognized-as-an-internal-or-external-command/ just tried it works.

Basics of Blender's CLI (Command line interface)
The command line is definitely the way to go. Here is a little training that should be enough to get anyone up and running:
blender

Is the command to run Blender from the command line (you may need to setup an alias to have this on Mac or Linux).
blender -b

-b is a flag that will run Blender in background mode. This is generally what you eventually want when rendering because it is generally faster. However, until you are confident with the command line, you may want to load the UI anyway, so that you can see what it's doing. To do so, simply omit the -b flag. Note that to do the rest of these commands effectively, you must ensure that you have the -b flag enabled.
blender -b filename.blend

Will open the file in the background, but still close immediately. This is not very useful, though, so we do something like this...
blender -b filename.blend -a

This will render out the animation as if you had opened the file and hit "Render Animation."
blender -b filename.blend -f framenumber

This will render out only the frame that was named, e.g.,
blender -b test.blend -f 10

will only render frame 10, then close.

Multi-file rendering
You can, however, string multiple files together. Suppose you are in a folder that has three blend files a.blend, b.blend, and c.blend. You want to render the 15th frame of a.blend, the entire b.blend animation, and the first frame of c.blend.
blender -b a.blend -f 15 b.blend -a c.blend -f 1

This command accomplishes this for us quite easily. Note that this is essentially the same thing as writing the following.
blender -b a.blend -f 15
blender -b b.blend -a
blender -b c.blend -f 1

In most command lines, you can also replace it with the following.
blender -b a.blend -f 15; blender -b b.blend -a; blender -b c.blend -f 1

Note that this is just the previous commands strung together on one line and separated by semicolons.

A bit about directories
There is something when using the command line called the current directory. You can change directory (the current directory) with the cd command. The above assumes that all of the blend files are in the current directory which means that you can leave off the absolute file paths.
Suppose in the command above, we want to access three blend files that are on the desktop. We could cd into the desktop (change the current directory to the desktop), so that the files can be accessed relative to that directory. On Unix systems (mostly Linux and MacOS), you could do something like this.
cd /Users/Username/Desktop/

The user's home directory has a shortcut ~, so this is the same as the following.
cd ~/Desktop/

Default preferences for the terminal probably open it where the current directory is the user's home directory, so you can probably just do...
cd Desktop/

To see what is in the folder you are in, you can use...
ls       # Mac/Linux

dir      # Windows

To see the folder path...
pwd      # Mac/Linux

cd       # Windows (just use change directory without arguments)

The clunky way - absolute paths
That said, you could just use absolute paths and completely disregard the current directory stuff. I wanted to avoid showing this because of the difference between Unix and Window's ways of writing paths. Unix separates folders with / and Windows separates folders with \. I'll be showing the Unix style in this example. Note the use of the ~...see above for what this means.
blender -b ~/Desktop/a.blend -f 15 ~/Documents/BlendFiles/b.blend -a /Users/Freddy/Desktop/c.blend -f 1

So if the Desktop is in the Freddy directory, a.blend and c.blend are both in the same folder.

Paths with spaces in them
One problem that you may encounter as Delagone mentioned in the comments is something like trying to navigate to:
/Users/Freddy/My Folder/

...where My Folder/ has a space in it. Because the command line separates arguments by spaces, you'll need to put double quotes around that argument to tell the command line to treat it all as one argument. For example, you could do something like the following.
cd "/Users/Freddy/My Folder"

This is one reason why most programmers tend to name folders without spaces; it makes it easier when working from the command line to navigate. Instead you can always name folders with camel-case MyFolder or with underscores my_folder.
If you are on a Unix-based system (I've not yet tested this on Windows), you can also escape the space and leave out the quotes. This is the default behavior for tab auto-completion on a Mac, while the quotes are default for Windows.
cd /Users/Freddy/My\ Folder/

The \ is the escape character and tells the command line to not interpret the next character in the usual way. In this case, it makes it treat it as a regular space character without separating them as arguments.

Thanks for the help! i will be testing this later today. I'm not quite sure how the commandline knows exactly where these blendfiles are located on my harddrive.

@Delagone This is if the blend files are in the current directory. I'll edit my answer to show some of this...

Thank you for the great answer! Finally got it working over the weekend.
Had some problems with the commandline not recognizing spaces in filename locations. therefore I had to use quotes. C:\Program Files\Blender Foundation\Blender\blender.exe should become "C:\Program Files\Blender Foundation\Blender\blender.exe" when using the commandline (current OS: windows 8.1) to prompt file locations. Note the space in the name Blender Foundation. It's up and running smoothly now. People like you make this site as awesome as it is. Keep up the great work!

@Delagone Glad I could help. These are just the basics of the command line that computer scientists just have to know. It's always wonderful to see other users capitalizing on this powerful tool as well. You're right about the quotes as well, I'll include that in my answer...

How is this different from the manual https://docs.blender.org/manual/en/dev/render/workflows/command_line.html ? If something is missing there, it should be added...

@brockmann This answer explains it clearly for those who are less used to the command line than you and I are. It is a different type of explanation. The manual doesn't need to (and shouldn't) look like this, but sometimes new things need more explanation than a listing of flags...

If you are linux user my answer would allow you to render all .blend files in a specific directory.
Open terminal in the directory and run the following commands:
First I,ll start by creating bash file

touch script.sh

Then give it permission to execute

sudo chmod a+x script.sh

Open the file,you can use your text editor or directly from terminal

nano script.sh
Past the following code :

#!/bin/bash
i=1
for f in *.blend; do
blender -b "$f" -P hi.py -f $i
((i=i+1))
echo $i ;
done

Run the script using :

./script.sh

You will find your renders in :

/tmp

Named as 0001.png 0002.png and so on.


text:
BGE: Which script names produce a "module has no attribute" error?
When I name a module script wave.py it breaks and I get this in the console:
Python controller found the module but could not access the function - object 'Cube', controller 'Python':
AttributeError: module 'wave' has no attribute 'main'

Any other (valid) name seems to work as expected.
Is "wave" a reserved name in Blender's API? If so, are there other such reserved names specific to Blender? Or have I overlooked something else?
Broken example (wave.py):

Working example (script.py):

Update:
I found that there is a module called "wave.py" included in Lib...
I also found this list of built-in Python functions, but it appears not to be exhaustive since wave.py is not included.
If someone can verify that this is the problem, and link to a complete list of built-in functions, I would consider it a satisfactory answer.
Update 2:
A complete list of built-in Python functions has been asked for on Stack Overflow. But the answers listed do not include wave.py, so is it not considered built-in? I'll rephrase the question: What are all the names I cannot use for Python scripts in the BGE?

wave is indeed a module from Python's standard library, as you can see in the link below. As it deals with heavy data processing (wave sound files manipulation), it is probably a compiled C extension, and you may find it as a .pyd file extension (which is equivalent to a Windows DLL). Refer to Python standard library to avoid using already taken module names and be a bit more specific about your own module names (like game_wave, and so on).
wave module on Python standard library documentation: https://docs.python.org/3/library/wave.html

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


text:
Keyboard shortcut for texture paint brush strength?
When texture painting the two most commonly adjusted settings are (in my experience) brush Radius and Strength. Radius already has shortcuts to decrease or increase: [ and ] keys respectively.
I want to configure a shortcut to similarly adjust the Strength.

From the console I can see that when [ is pressed this happens:
bpy.ops.brush.scale_size(scalar=0.9)

And when ] is pressed this happens:
bpy.ops.brush.scale_size(scalar=1.11111)

Here is what the key configuration for [ looks like:

So I am hoping there is some kind of corresponding command for Strength, but nothing I've tried has worked.
For example: brush.scale_strength does not work.
Is it possible to set keyboard shortcuts for the Strength slider?
Thanks

Why doesn't Shift+F work? Also there's F command for brush size; they are the same as [ and ] but no need to get to that part of keyboard

@MrZak Yes, of course! I had forgotten all about F and Shift F! (facepalm) Thank you! Still a bit curious if other sliders can be customized to be set up like Radius, but for all practical purposes the F shortcuts are just what I need. Cheers.

There's addon Sculpt/Paint Brush menus (likely shipped with Blender) which asigns to some keyboard shortcut and you can get to whole paint menu with it

@MrZak Thanks! I just tried it. “Sculpt/Paint Brush Menus” It's good for freeing up screen real estate while painting. I assigned its shortcut to my Wacom pen. Nice tip. :-)

EZ Paint (formerly Texture Paint Plus) also has popup controls on W/Shift-W/Ctrl-W etc and enables me to go full screen when painting. https://github.com/artistCDMJ/ez_paint/archive/master.zip

Use Shift+F for Strength, F for Radius, and Ctrl+F for rotation of brush texture.
When using a brush texture in Stencil mode, RMB to move, Shift+RMB to scale, and Ctrl+RMB to rotate the stencil image.
When using Stencil in Brush Mask, Alt+RMB to move, Shift+Alt+RMB to scale, and Ctrl+Alt+RMB to rotate.
I use these all day, and prefer them to the typical  [ and ] usage in photoshop and other editors.


text:
Blender halftone pattern filter
I am trying to set up a material that acts as a filter - taking an image plane and giving it a halftone look.
The dot pattern is made wih a radial gradient texture mapped across the camera space. A Group Node that replicates the functionality of a ColorRamp (thanks @PGmath!) takes advantage of that radial gradient to manipulate the dot radii using the original texture - which is split into CMYK channels.

CMY are generated by separating the three RGB channels, and recombining two of them while omitting the third. These three C,M,Y dot patterns are then multiplied together along with a black (Key) channel and it looks somewhat like halftone printed artwork, but it has the following problems:

Cyan seems to be too strong in areas like the fire, where it shouldn't be, and weak in the bluish background where one would expect it to be more prevalent. When multiplied it actually darkens the fire. That's how the multiply blend mode works, but how the darker color values got so strong in those areas to begin with, I'm not sure.
Areas with a lot of black lack color in between the black dots where one would expect it. (Color is dropping out in dark areas.)
Dot size seems to be disproportionate in each of the CMYK channels. Magenta has really small dots compared with Cyan, for example.

Here is the node setup so far:

You can see my desperate attempt to balance the color channels using RGB Curves nodes. This was pure trial and error. There must be a better way.
I suspect that part of the issue lies in that C,M,and Y each have very different levels of perceived brightness. So maybe I need to correct for this before the color data is converted into dots. I'm still researching about this.
If you guys see where I'm going wrong here, please point out my mistakes. Thanks!

Related (using compositor instead of shader) : https://blender.stackexchange.com/a/99462/29586.

By inverting the RGB channels before splitting them I was able to create a working setup that is also easier to understand.

Here is the new node setup:

There are a few things that can probably be tweaked and improved, but in essence the problem is solved.

I played a bit with it and noticed, that it was the conversion from RGB to YCM.
R,G,B = 1,1,1 should be converted to Y,C,M = 1,1,1
But it doesn't. Try it out and here a custom conversion for workarround:

I think you might be onto something with that color separation method. Thanks for posting that. I just have to get it back to a subtractive color model, because the way the colors are combined in your .blend it is additive like RGB and has no black channel. I'm experimenting now...

Would be good to add an image preview as well so those of us passing don't have to grab the blend and render. :)


text:
Is filmic blender already included in Blender 2.8?
Is filmic blender already included in Blender 2.8?  I'm referring to the filmic blender from sobotka.github.io/filmic-blender/.  The blender guru had a tutorial on lighting.  In which, he mentioned downloading this for blender 2.79.
Thank you.

Yes but still would go to github myself. https://blender.stackexchange.com/questions/107372/are-there-significant-differences-between-filmic-shipped-with-blender-and-its-de

Yes, Blender includes the view transforms Filmic and Filmic Log. The implementation in Blender was originally created by Troy Sobotka, who independently continues the development in his own repository.

Thanks for all your answers!

@YanIronmonger If the answer solved your problem, please consider marking it as accepted by clicking on the checkmark next to it.

You can find the view transform option under render properties/color management. Here it is already set to filmic.


text:
how to create a light streak(trail) in Blender 2.8?
Does anyone know how to create a light streak(trail) in Blender 2.8?  this following tutorial shows how to do it in an earlier version of Blender, but I could not make the smooth light streaks in the 2.8 version.  The light streaks came out as a bunch of particles, not smooth.  Thank you.
https://www.bing.com/videos/search?q=how+to+create+a+light+streak+in+blender&docid=608041268300154275&mid=3CBA7361FBC00C4E69C43CBA7361FBC00C4E69C4&view=detail&FORM=VIREHT

Here are a couple more some dealing with particles https://blender.stackexchange.com/questions/93921/how-to-add-trailing-light-effect-to-finger-tips/94976#94976 https://blender.stackexchange.com/questions/112746/atmospheric-trail/112753#112753

Thanks for pointing me to a similar post.  It really helped.


text:
how to assign different physics to different particle systems?
I'm trying to set up 2 different particle systems in my animation, one with "wind" blowing the particle system upward, one with a different particle system making a light streak.  The wind blowing the first particle system takes place first, but when I try to set up the light streak particle system, the "wind" for the 1st particle system blows my light streak upward too.  Is there a way to assign different force fields in physics to  particular particle systems?  Thank you!

I might have figured out the simple solution.  Setting up the "field force settings" in the corresponding "Particle settings" solved the problem :)  If anyone has better ideas, please share.  Thank you!


text:
how to use the color spill node?
could anyone share some knowledge on how to use the "color spill" node in Blender's compositor?  Is there any tutorial on this topic...I could not find any.  I need to reduce the background color reflection onto the foreground objects.  Is the color spill node the best tool?
If not, please advise better ways.  Thank you!

I haven't watched it since I don't need it... so I don't know if it's a good tutorial... but since you couldn't "any", here's one to begin with: Color Spill, Color Key, Luminance Key... EXPLAINED. And since you ask what is the best tool and I don't know exactly what you want to do, maybe this helps: Chroma Removal in Blender | Keying in Blender | Green Screen Removal

Thank you!  I make room setting furniture renderings.  Sometimes the ambient lighting or wall colors reflect onto the furniture, making the color finish look a bit different.  The tutorials you've recommended are very helpful.


text:
how to smooth jagged edges?
Please see attached picture.  Blender seems to have trouble with curves.  Even after applying "shade smooth" or "line by crease" from MeasureItArch, the curves still appear jagged.
I originally thought it had to do with imported WRL files, but I had a similar issue with a cylindrical shape created in Blender, too.  Is there a good way to smooth these curves out?  Thank you.

Do you know how to use the Subdivision Surface modifier?

This is entirely normal.
You can turn up the resolution of the curve in the Properties editor.
Explanation: In CG, all surfaces are secretly made up of flat pieces. The trick is to get enough of them that you don’t notice. Shade Smooth fakes the way light interacts with the surface into looking more smoothed, but does not alter the geometry. If you 3D printed a model in two versions, one shaded smooth and the other shaded flat, they would come out the exact same way.

Noted.  Thank you!


text:
Is this add-on "Extra Lights - Photometric Lighting For Blender" compatible with Blender 2.90.1
Does anyone know if this add-on "Extra Lights - Photometric Lighting For Blender" is compatible with Blender 2.90.1.  Here's the link to this add-on from blender market place:  https://blendermarket.com/products/extra-lights.  Thank you!

Yes, it is compatible with Blender 2.90.x. At the time of writing, this add-on will work in Blender 2.82 and later. The current version of the add-on can be found on GitHub, excluding the presets that are in the paid version.

Thank you so much!  Yes.  I did hear about the free version in GitHub.  Will you please explain the "presets"?  Are they lights that the creator has set up?  Do most people prefer the convenience of having these presets?  Thanks.

@YanIronmonger I haven't bought the add-on, but based on the description the "presets" refer to both IES files and defaults for different lamp types. IES files describe the light intensity distribution of a light source, which is basically the light pattern it casts. This is certainly useful when trying to recreate realistic light sources. I can't answer what the general preferences of most users are and whether or not this would be useful to you.

Thank you so much for your opinion.


text:
Need help my object isn't showing
could someone tell me how to solve this problem?

Your object is in fact showing. You can see the edges connecting vertices (which are not displayed in object mode). If you want a face/polygon then you will have to create one.

thank you, now is showing

Great that you found a solution. I encourage you to add an answer detailing the steps to solve the problem. That way others can profit from the solution as well.

Sorry, I should have been more clear. Please copy paste your answer in the answer box below. That way, others can upvote it and you can mark it as the correct solution. =)

Solution: Press L to select the whole object, then go to edit mode, pressing TAB, and click the hotkey F. To add a face in the object.


text:
Mix node as identity function
What is the difference between the following two node setups?

I was hoping to use the mix shader as a scaler, but it's not behaving as I'd expect..
Here are the render results:

The "direct" line is much stronger than the one going through the mix shader.

This is because you are using a Mix shader (Add node > Shader > Mix).
This does not work because:

A color output (yellow socket) is not a valid shader input (green socket).
A shader output (green socket) is not a valid value input (gray socket)

If you instead use a Mix RGB node (Add node > Color > MixRGB), it will work as expected:


text:
Scaling the distance between objects
I've got a camera tracked to an empty, and I'd like to add keyframes with constant interpolate to have the camera "click" forward.
How can I scale the distance between objects, without affecting their size? Even better would be setting an absolute value of the distance between the objects.

There's a button in the header bar (three dots with a left-right arrow under it) that when switched on means that your transformations will only apply to the centre points of the selected objects. Using that tool and pivoting by active element will allow you to scale two objects, keeping one in place, moving the other away or towards the active object and leaving the scale of the actual objects themselves untouched.

Setting the absolute distance between two objects could be done with a "Limit Distance" constraint set to a Clamp Region of "On Surface", which you could then key the distance value for.

Is it possible to do this to selected vertices, edges or faces is edit mode?

No, I don't think so. You can scale using a single face, edge or vert as the pivot point (active element pivot mode), but the relative distances between the other elements will scale up and down, meaning that the "bits" you're moving will get bigger and smaller.

Thanks. It turned out that I could accomplish what I was looking for by extruding faces along their normals (ezz)

In version 3 this is in the "Options" dropdown on the top right


text:
How to render without evaluating keyframes?
I've got some keyframes set up and don't quite like the way things look. I'm playing with some values to see if I can't make it look nicer.
When I render to see the affect of my changes, everything pops back to the keyframed (or interpolated) values. Is there a way to render the current state of the scene, regardless of any keyframes?

You need to mute all channel in current object's animation data. Muting Actions and NLA strips can be done by pressing LMB on speaker button at each action channels or NLA track.
A faster way if involving lots of channels/tracks is to press A with cursor placed atop channel list to select all channels (or select channels manually with Shift-LMB), then press Shift-W, and choose Mute:


text:
Rendering with wireframe
I'm making figures to illustrate some details about how meshes work. I'd like to render my scene normally, but overlay all of my meshes in wire mode.
The only solution I've found which works is giving a duplicate mesh a wireframe material, which gives me something like this:

Is there some way I could get the same effect without having to duplicate my mesh?

Cycles or BI? related: http://blender.stackexchange.com/questions/2372/how-to-render-a-pixelated-occluded-wireframe-with-freestyle and http://blender.stackexchange.com/questions/605/can-cycles-wireframe-material-be-coerced-into-displaying-tris-quads-and-ngons

BI.. for the only reason that I've never tried cycles.. would cycles make this easier?

There are several ways to do this:
Freestyle:

In edit mode, select all and press CtrlE> Mark Freestyle edge

Enable Freestyle in Render settings:

Enable Edge mark in Render layers > Freestyle line set > Edge types:

Render.

Wireframe material:
Another way is to use a wireframe material as described in this tutorial:

Add a material and select Wire, enable Z Transparency and set the Z offset up to ensure the wires are rendered above the clay:

Add another material and assign it to all the faces.

Render:

There is a simple addon for this called Setup Wire Materials.

A script to setup and apply materials for a wire render… It will replace your own with a clay and a wire materials, as seen here and here.

This looks great, but I accepted gandalf3's answer because it worked with Blender as-is, without having to download anything extra.

Incoming Blender 2.7 have the Wireframe modifier. The tool replaces the object of his wire.  You can set thickness and different material for wires. Short tutorial (1:44) is here https://www.youtube.com/watch?v=ZgaFHDVFCMQ

You should take the valuable information from the tutorial and paste it in here. You can still link to youtube but the answer should be stand-alone

OK, thanks for suggestion. I was thinking that it will be faster and more understandable.

I hadn't noticed the wireframe modifier before.  Thanks.

Alternative method:

Go to the overlay options and select overlay (disable other things if you want to clean the view)
Change the color of wireframe on the blender options to white, or other color (black is usually hard to see). [Options -> Themes -> 3D ViewPort -> Wire)
Menu View -> ViewPort Render Image

credits to:
https://www.blendernation.com/2020/05/19/quick-tip-render-wireframes-in-blender-and-eevee/

You can use the Wireframe Modifier. For that, go to the modifier tab with the object selected (I suggest making a copy of it, so you can have both the object and the wireframe), add the modifier called Wireframe under Generate (at the bottom), then you can change the Thickness, Offset and more.

More details please, we need detailed answers here.


text:
How can I get a cabinet projection camera?
How can I get a camera to render with a cabinet projection?
I know it is possible to get a gaming isometric projection, but that's not really what I want.
I've tried positioning an orthographic camera in almost all possible ways but still can't get one. Actually an orthographic camera wouldn't work because as soon as you get the world x-axis parallel to the viewport x-axis, the world y-axis is always parallel to the viewport y-axis.
I think it is something like shearing, but I am not so sure.
Cabinet projection:

Image from Wikipedia

Shearing can be accomplished using the Shift camera setting.

@Aldrik, that works with perspective, but doesn't affect anything in orthographic.

You may use a FOV value below 1 degree, put the cam very far away (to the proper distance), and shivt the camera (with a value around the cams distance). Such low FOV will result a render that looks like isometric. (Actually nearing 0 with FOV will LIM the image to the isometric.)

@RóbertLászlóPáli yes but that introduces problems of its own: you'll need a huge range of camera depth, for one thing, which could lose precision as well as causing unnecessary BVH calculations. When Cycles gets volumetric rendering, that could result in an undesirable increase thereof (because you're going through a ton of fog just to get to those objects). It also might mess with emission, but I'm not sure.

Demonstrating in 2D what is going on:

Mathematically it should be correct to render with a orthographic camera
and later transform the image. I think this is the easiest method when
you have multiple objects (so you do not have to add modifiers to each).
First you should shear in 2D (skewing) the rendered image then (if needed)
stretch to get the correct aspect.
Original:

Sheared:

Streched:

Most raster graphics editors have the tools to preform the above
transformations. This can also be done in the compositor using a
Blend texture and the Displace node.

On the sheared image you can actually see some strange anti-aliasing effect, not perfect, unfortunately. Also, scaling will result in a lower quality. Though this is definitely a possible way...

Yes, quality gets worse sadly, but you could render the image twice as big (for example) and then scale it down, this will smooth out the quality loss, but costs render time.

Could just deform the model

Point your orthographic camera down the Y-axis.
Create a lattice Shift+AL with the following number of points:

Enter Edit Mode Tab, select all points A and perform the following rotations:

RZ-45Enter
RX45Enter

Finally add a Lattice modifier to you model(s) with the Object set to our previously created lattice.

Hmm… I tried your solution, but still getting isometric render


text:
What file formats preserve sharp edges?
I am collaborating on a project with another individual who uses 3DS Max. When he marks edges as sharp, exports the mesh as a .obj file and gives it to me, I don't see any marked sharp edges.
Are there any file formats that preserve sharp edges between modeling programs that I can use in Blender?

you can export using the edge split modifier, that's not quite the same though. Also I have not used .fbx in a while but maybe it now supports sharp edges.

Have you tried the last Blender version ? I've seen that it now supports sharp edges with vertex normals, so no more edge splitting needed. That should theoretically works as Max is using something similar (You might have to use FBX export thought).
If that doesn't work you can still collapse the edge split modifier prior to export, it will break your sharp edges in two. It's less practical but gives the same visual result.
If you're doing models for realtime keep in mind that sharp edges splits the uv islands in most game engine, which can very slightly reduce performance (sometime support edges are a better option). Cheers !


text:
Why are my mesh edits reverted?
I've received a model from someone else. Any changes I make to the mesh in Edit Mode seem to be undone when I return to Object Mode.
On the left is the mesh in Edit Mode, on the right is the same mesh in Object Mode:

Try going through the following checklist:

Check to see if the problem might be caused by Modifiers.
Try turning off or deleting Shape Keys on the Object Data tab.
Clear out any Keyframes
Clear displacement and rotation of bones
Try removing the armature from the object


text:
Building a Conveyor
How would I build a Conveyor like this in blender?
Thanks

You can use Rigid Body physics with Constraints to replicate this:

Add a cylinder and make it an active Rigid Body object (CtrlR)

Add a cube and make it a passive rigid body object (CtrlShiftR), and move it to the side of the cylinder.

Constrain them together (Tool shelf > Rigid Body Tools > Connect) with Hinge constraint and rotate the resulting empty 90 degrees on the Y axis:

Constrain again with a Motor constraint and enable angular motor:

Duplicate

Cool. What about making it follow a curve like in that video. The conveyor ain't straight.

@00Ghz You could use some of the techniques here, using an plane with array and curve modifiers as the emission mesh.

@gandaf3 same way i have my question but nobody answered it can u plz answer http://blender.stackexchange.com/questions/66456/how-a-physics-motor-and-slider-works


text:
32 bit iMac, will 64 bit run properly?
I am ready to download Blender. I have and older iMac, 20", 32 bit. It has memory upgrade to 4GB and the latest Yosemite. I only see the option for 64bit for download. Is there still a 32 bit or does it not matter?

If your system is 32bit, load blender's 32bit version. If it's the wrong one it won't run on your system. :)

This question appears to be off-topic because it is  about operating systems and not in scope.

I don't know specificity for a mac, but in general a 32bit program will run on a 64bit system. However it will not work the other way around, you can not run a 64bit program on a 32bit system.

Thanks everyone for your comments. Sorry the question is off topic. I'm new to this forum and navigating is a bit awkward for me. BTW, Downloaded latest version of Blender, it is working fine. Now if only I can learn how to use it.....;)

Blender dropped support for the 32bit versions of OSX in 2.72.
To your question about running a 64bit version on your 32bit system, I will direct you here.
If you find that you can not use any 64bit software, because of your CPU or some other reason; then you can still use 2.71 with no problem.
Download link for 2.71 32bit OSX on blender's server.

Thank so much David!! The secondary thread you directed me to answered the quest and instructed me on how to find if I am running 32 or 64. Turns out I am running 64 bit. This is one less thing for me to worry about, thanks again!


text:
How to know when object are deleted?
I use blender as a network client. I'm able to know when objects are updated (via handlers). But I would like to notify the server when a object (or mesh, animation, etc.) are removed, how can I do this? (Should I keep a list of all objects, and compare with existing?)

I would try saving a list of object names in a scene_update_pre function then compare that with a scene_update_post list of objects.


text:
Smoke missing from jpg output
I have a model (v2.69) that renders smoke in the viewport. However while the model appears in the jpg output the smoke does not.  Every thing is in the same blender layer.  I have recently re-built the machine to Ubuntu 14.04 and the problem persists.  6mths ago it was fine, the hardware has not changed and the example files are in http://blenderartists.org/forum/showthread.php?338435-Where-can-I-get-some-advice
GIMP works fine, the machine works fine and so this is looking like a Blender setting and something that is stopping the smoke from getting to the output file.
Stuart

Welcome to Stack Exchange Blender! Could you please add more detail or a .blend file so we can help you.

I doubt it's a hardware/driver/os issue, as rendering is done on the CPU (I assume you are using BI, if not, then cycles volumetrics are not available on the GPU or CPU in 2.69). More likely something happened in the upgrade (2.69 didn't exist two months ago, so I'm assuming you upgraded).  As GiantCowFilms already said, a blend would be helpful :)

I've just uploaded test.blend to pasteall.org and cant see a link to send?

@user4953 Just copy the url from the top of your browser and post it here.

Link: http://www.pasteall.org/blend/30217 to the blend file.


text:
Different number of Vertices, Faces and Triangles between object mode and edit mode
In object mode it says that I have 1 of 99 objects selected and over 10000 Vertices, 2000 Faces, and a similar high number for Tris. When I tab into edit mode it shows the actual numbers of the object, 28 Faces, 100 or so Vertices etc. It is the only object that I have, I see nothing else. I have no idea what the cause is, when I delete said object everything goes to 0 again. So it doesn't appear to be extra objects that I'm missing. What would cause this?

Do you have any modifiers on the object? That would cause the difference you are seeing.

This is happening because you may have a modifier on the object that does not affect the mesh during edit mode, but the changes are shown in object mode.


text:
Animating along a path with some rotation?
I've got a "flubber" like character model. I'm trying to animate the model along a path and add a playful rotation of the model at certain points along the path. I've successfully animated the character along the path using the 2 most common methods (a) parenting method (b) follow path constraint.
Ideally when the model descends at a point I would like to have a 360 degree spin, but Blender doesn't retain the keyframes I've placed. Is there solution for this?

How exactly are you rotating and keyframing it? (this should be working). If you rotate with R the rotation will be normalized, which would make it appear as if nothing happened. If that is what's happening, try animating from the properties region (N) instead.

I set a keyframe (I) at the start of where I want a spin and then set a keyframe (I) at the end of the spin. I use the Transform panel (n) to make my adjustments

You can if none of the other solutions work, parent an empty to the curve then parent the object to the empty.

That's how I have it currently configured.

Update: I've parented the Empty to the BezierCurve using "Path Constrain" and I have "follow" checked on in the path animation of the curve. I've been successful in adding some keyframes that start a rotation, but they are acting really weird.

Apparently the order in how you set the keyframe is MAJOR. I would set the keyframes then make my adjustments in the transform panel. From what I've seen  in the past half hour it's best to make your transformations then set a keyframe. If you want to adjust a keyframe, then you use the graph editor.

@user5071 When you set a keyframe, it stores the current transform values for that frame. If you make any changes after that you will have to set the keyframe again, since it doesn't auto update.

You can use Ctrl-T on a curve point to 'rotate' the point, the object following the path will also follow this rotation.


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Low polygon modeling vs good topology

In the picture above you can see two staircase. The top is modeled with 32 triangles to cleanly fill the gap beneath it. The lower is modeled with 2 triangles that are disconnected from the steps above it and serve to only fill the hole. When having a low polygon count is a requirement is there any reason other then not having clean topology to not create your models like the lower example?

This question appears to be off-topic because it is not about blender.

That's a little harsh. If the OP showed a screenshot of the blender interface with this example i doubt anyone would question it.

This is a perfectly fine question.

@RayMairlot See http://meta.blender.stackexchange.com/q/312/599 for discussion.

If you care about the real time performance of your model, then forget topology and focus on removing every single unwanted face(poly). You may, when modeling keep good topology in order to expedite and simplify the process. At the end you can go back and remove the remaining extraneous faces before moving onto UV unwrapping and texturing. That is purely a matter of preference. If you don't care about the real time performance, then by all means focus on good topology.

It's much easier to modify the upper version afterwards than the lower one. the lower one would be totally messed up if you'd change anything in the mesh. I'd recomment to find something in between.
I would propably use quads instead of triangles below the stairs in the upper example.


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How to create icicles hanging off an object?
Is there a way to create icicles,
for example like this:

I was thinking if there was some way to use a Snake Hook brush on many random places at once with different strengths etc., but I don't know if this is possible.
How can I achieve this?

Image from Wikipedia

Icicle Generator
This addon creates rows of very realistic icicles along all selected edges of an object. You can download and read about it here.
Here is an example of how beautifully they render:

To enable Icicle Generator:

Download the addon by clicking here.
Open the User Preferences:
Info header → File → User Preferences

Click on Addons at the top of the Preferences window, and then click on the Install from File button at the bottom of the window:

Next:

Find the addon file and select it (the file can be a .zip file -- you don't have to unzip it first)
Click the Install from File button
Then enable it by clicking the checkbox on the far right of the addon
If you want Icicle Generator to be enabled by default in the future, click on the Save User Settings button:

To add icicles to an object, the object must be a mesh. If it is a curve object, simply convert it to a mesh object with ALTC → Convert to Mesh
Go into Edit mode, select all edges you'd like to have icicles hanging from, make a copy of those edges and make them a separate object:
SHIFTD  → ENTER →  P → Separate Selection

This will create a new mesh object composed only of the edges where you want icicles to be.
NOTE: Don't move this icicle edge object -- it's in just the correct place now.
You MUST apply the icicle edge object's Location, Rotation and Scale while in Object mode before adding the icicles:
Object mode → select object → CTRLA → Location → CTRLA → Rotation & Scale
Now select the newly created edge object, go into Edit mode, select all, and add the icicles:
Select edge object → TAB → select All (A) → SHIFTA → Icicle

To adjust the settings, open the Tools panel (T):

These settings (above) yield icicles like this:

However, if you want a more random appearance, set the Min D to 0.2 and Min R to 0.01 -- this causes some icicles to be so small they appear to not be there, yielding icicles like this:

NOTE: You MUST set all the settings the way you want them to be before you do ANYTHING else, otherwise they cannot be changed again.
Now rename the newly created icicles object to "Icicles" and assign them a Glass material:

If you want to, you can give the icicles a bump texture.

You could use a Particle System of type Hair.
Make a plane and apply a particle system to it.
Also make an icicle as a separate object, or make several and make a group out of them.
Remember to set the origin of each icicle to where it should start growing on the plain, and also CtrlA apply rotation&scale.
In the particle system properties, go to Render. If you made just one icicle, choose the Object tab and your icicle as Dupli Object. If you made several, go to Group tab and choose your group.
Then play with settings in particle system to get correct rotations, placements and scale. Randomness can be applied to all.
Here's a quick result with only one icicle object (open image in new tab to see full size):

Edit:
If you want to fine-tune location of icicles, set Particles/Face = 1 and edit the faces on the plane to exactly where each icicle should originate. Remember to set matching count to amount of faces.