text:
Simple rotation... impossible?
I'm feeling crazy, why is it so hard to just rotate objects predictably in blender?
No matter what setting I use, I cant get things to rotate how I want to.
Watch these two webms. Imagine the front beveled face is the face of a human and I want him to look up = rotate his head back a bit.
It would stand to reason that blender has some kind of internal object rotation right? Well that setting doesnt work either. Nothing works for me.

Pathetic attempts to make it work but I cant:
http://webm.land/media/reS6.webm
http://webm.land/media/9cqn.webm

Not exactly sure what you are asking... put try turning on the spherical rotate transform tool -- the gyroscope looking one. That allows you to rotate specifically by X Y and Z. Using the Transform Rotation sliders on the N tab will too... Rotation occurs around the object's origin, which you can position as/where you like. Some rotations, like the head rotation you mention, can be made even more natural looking with armatures.

https://docs.blender.org/manual/en/dev/editors/3dview/object/editing/transform/basics.html#rotate

I'm pretty sure, you want to rotate the object around its local axis. To do that, choose local transformation orientation and then access it with shortcuts by pressing R, X, X. The second x (or other axis) keypress switches from global to whatever transform orientation is selected from the dropdown menu.

@Leander I already did that, the second video shows axis locked rotation while local axis is selected. Still doesnt change the weird behavior. Yes, I can use the rotation gizmo just fine but this is supposed to be the faster and easier way yes? Well it doesnt work at all for me.

If you want to rotate on its own angle, do as Leander says (if it doesn't work properly, perhaps you have made a rotation of your cube in Edit mode?). If you want to rotate it around a different pivot than its center, move the 3D cursor to the point that is supposed to be the pivot, and select 3D Cursor in the Pivot Point  dropdown menu on the horizontal bar on bottom of the 3D view.

@moonboots please explain this then, I made a new cube and I definitely didnt make any edit rotation (how would I fix that then? I already tired 'set origin to geometry', didnt fix it). As you can see, the rotation gizmo works totally different from the rotation shortcut. Why?! http://webm.land/media/TCVd.webm

it looks like this time you have enabled the Local orientation on the dropdown menu of the horizontal menu bar. If you want to rotate your cube on its own axis, you can either do it with the widget, or pressing keys. In the second case, you still have to press R and twice the axis. Now, does it rotate around the axis you want? By default it will be its origin point, but you can change the rotation pivot with the Pivot Point dropdown menu of the horizontal menu bar.

ohhhhh twice the axis.... well I didnt know that, it makes no sense with what the gui is showing though. If I select local up top then I expect all rotations to start locally....and the popup actually seems to do something completely different, I havent figured that out.

The dropdown menu is just to display the 3D manipulator widget.

The solution appears to be literally what I wrote, please read more carefully! The transform orientation which is selected from the dropdown is the one which is used after pressing the axis key (X/Y/Z) the second time.

Where the object "Origin" is will make a difference.

It looks from your video as if you are rotating on the Global (World) axes, where what you would like is a rotation of the cube about one of its own local axes. If you haven't reoriented the cube in Edit Mode since it was created, its local axes will still run from the cube's center through the centers of its faces.
In that case, as you have, you can just set the Transform Orientation (in the header at the bottom of the 3D View)  to 'Local'. Set the pvot point to the center of rotation you want ..(e.g. 'Individual Origin(s))
The primary, default, orientation for transformations is always Global. To reach the secondary orientation ( the one in the header ), you have to hit the constraint key(s) twice. So hitting RXX, RYY or RZZ  will let you rotate the cube around its local axes.
(If you rotate all or part of an object's mesh in Edit Mode, that's all you have rotated. The object's local axes remain where they were before the edit.)

(Oops. I've just repeated Leander's comment)


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Rigid body activates, before it interacts with another object

I want the pitcher on character's hand get hit by a plate and fall and then I want other plates to destroy the rest of the character but everything falls apart even before plate hits anything.

If you want the simulation of an object to start on a specific frame, keyframe its animated property to be enabled during the animated part and disabled as the simulation is supposed to start.

yes learn how here:
1-3 // https://www.youtube.com/watch?v=DEo_9AopfoQ
2-3 // https://www.youtube.com/watch?v=QY7iJmqsJf8
3-3 // https://www.youtube.com/watch?v=G0VJmmPPvwA
Enjoy!

please do not paste links without any notes about what they contain. Any links should supplement your answer not be your answer.

Oh, OK thank you I will know from now on!
Sorry about that.

source: Stack Exchange

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

sort: votes


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Can i render particles from one object on 2 different render layers?
I am following one of CG Geek's tutorials about Fall Road and i am having a problem with final render. There are about 6 different particles systems on one object and my PC just can't handle it. It freezes when i try to render. I was wondering if i could somehow move some of these particles systems to different layers so i could render them one by one and then connect them in composition?

Are you sure it freezes and doesn't just take a long time to setup before it starts rendering?

Well, i am not 100% sure, but i've waited for 30 min and it still was on synchronizing object.

There are no settings to define which render layer a particle system is render on, the particles will all show on the same layer as the emitting object.
You could setup multiple objects, each with their own particle system and placed on a separate layer so you can render them separately. By using the same mesh, the particles can emit from the same positions and parenting the duplicate objects to the main object will let you move them all together. You can also disable selection of the duplicates so you can only select the parent object. The particle systems on each duplicate object would then have the render emitter disabled to prevent them from showing in the render, so you don't get z-fighting.

Well, i am a newbie so could you explain how can i do it step by step? I duplicated my object and moved it to another layer, then unchecked emitter, but it still was visible so i created mask modfier on it and then i rendered it, but i don't know how can i "merge" those render layers together. I tried in composition, but it just makes one of the layers partially invisible

You could start with the blenderguru introduction to compositing his recent rendering onto an image also applies. You can find several examples here, this one explains getting scene layers onto a render layer, this one shows using an objectID as a mask when mixing layers.

Well i don't know if i did everything good, but at least i finished it :D Thank you for your help.
Here are the results
fall road

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


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Importing fbx animated character, mesh deformed
I'm trying to import animated character from motion builder to blender. I still get though deformation like this. How can I approach fixing it?

Seems to me you have to weight paint some bones to the appropriate part. Have you tried disconnecting the armature from the model and see if it snaps into place? Or unassigning all vertices from the bones in the vertex groups tab.

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


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How to get the smoke animation to disappear after end frame
I have made an animation, which lasts from frame 1 to 3600.
Within this frame range, I have made another animation from frame 2260 to 2600.
The problem is, that this smoke animation from 2260 to 2600, does not disappear after frame 2600. It just freezes and stays as it was at frame 2600 for the rest of the animation. Instead I want it to disappear.
Do someone know how to do that using blender internal render?
Thanks for your help.

What render engine are you using?

Blender Internal Render

Do you want the smoke to disappear all at once, or disintegrate smoke-like?

Ideally it would disintegrate in half a second or a second.But if that´s not possible, disappearing all at once would be quite all right. It´s an animation of an astroid going through the atmosphere and burning up.

I added another answer showing how to get the smoke to dissolve.  I'm not quite sure it's exactly what you are looking for, but try it out and see if it does what you want.

If you want the smoke to dissolve gradually (as opposed to just disappearing all at once) you can enable Dissolve under the Smoke rollout of the domain object's Physics properties panel.

To be clear, this does not make the smoke dissapear all at once at a certain frame, rather it makes a given smoke particle dissolve after a given time.
Here is a comparison with Dissolve enabled on the left and disabled on the right.

Thanks again for your advise.
But the strange thing is, I have already enabled dissolve. I have now tried again with the exact same settings as in above screenshot and baked, but still the smoke remains after frame 2600. Can it perhaps be some other setting?
How should I go about if I wanted to make the animation disappear all at once instead?
As an alternative solution I could just render image 1-2600 and then delete the smoke domain and then continue to render, but I guess thats  not really the way to do it.

@Oscar  You can animate the visibility of the smoke domain.

Thanks, I see your discription above, I will give it a try...

@Oscar  If an answer has sufficiently solved your question you can mark it as accepted by clicking the checkmark under the voting buttons.

Note: this answer was posted before the OP specified the BI render engine, I am leaving it in case future viewers are using Cycles.
If you are using Cycles you can make the smoke disappear at a certain frame my simply animating its material.  To do this add a mix shader node and plug your smoke nodes into the bottom socket, leave the top socket empty.  You can then animate the mix factor on the mix shader to make the smoke disappear.

A value of 0.00 will give no smoke while a value of 1.00 will give full smoke.

Thanks for your help, it´s much appreciated. Unfortunately, I am not using Cycles. I should have mentioned that.
I used the in-build Quick smoke animation in blender render to create a fire. Do you have any suggestions on how to make it disappear in blender render?

Another option is to animate the visibility of the smoke domain.  Just go to the Outliner and keyframe the little camera symbol next to the domain object by hovering over it and pressing I at the frames where you want it to change.  The eye symbol controls the viewport visibility of the object in the viewport, the camera controls the visibility in the render.

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


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How can I create a bump line across an object using textures?
I want to create a photo realistic lego man in bender cycles.
But the problem is that I cant figure out how to use my black and white texture
to make this little bump line across the lego minifigures arm.
My scene.

I want the result to look like this.

It's driving me crazy!!!
Please Help.

I think the piece you are missing might be UV Unwrapping. In edit mode select the vertices of the arm and position the uv's in the image editor so that your bump line is positioned where you want it on the arm.

I already unwrap it with project from view.

You can do the following...

Add a Bump Node
Add invert node to your bump map texture.
Plug it into the height input on the Bump node.
Plug the bump node into the Normals channel of your shaders.
Adjust the strength value on the Bump node, to match your need.

Note bump is exaggerated for demostration purposes.

Here is the blend file.

Thanks for the quick response. But now I need my other texture to go over the bump

You can add your texture map on the diffuse channel.


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Position a menu entry into a specific location with python
I have a plugin that selects all polygons by the vertex color:
https://gist.github.com/tamask/2590850
However, in order to use it, I need to search for its menu entry 'Select by color', using the space bar search. Is there any way to position the menu entry 'Select by color' wherever I want? Idealy I want it in the Ctrl+G menu, that is in 'Edit Mode': Select > Select Similar > Select by color?


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View vertex color in edit mode instead of material color?
I am using vertex color to create the colorID map for Substance Painter. I canot use materials for this, because I use materials to define Substance Painter's textures sets (there is no other way for the latter as far as I know). Is there any way I can view the vertex color in the viewport, when I am editing the model in the 'Edit mode' instead of the colors of the materials?

It should be possible to select Attribute node with mentioned vertex colors, press Ctrl+Left click to preview selected node and then enter Material mode in 3d viewport (essentially previewing material but when it's set to show vertex colors).

Could you show a guide/explain in details how to do it? I am new to blender and it is really hard to even try to follow you.

A quick gif of previewing vertex colors in Edit mode with material shading mode

In Blender 2.8+, select Solid viewport shading and click the arrow button to bring up the viewport shading menu. Set Color to Vertex. Setting Lighting to Flat may also be helpful.


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Is there any way to reduce the spaces between UV islands without scaling the actual islands?
I know about Ctrl+P, I know about Individual Origins scaling, that is not what I am looking for, I am looking for the scale tool that reduces empty space between a selection of scatered, non-uniform UV islands without actually scaling said islands. Any suggestions?

When you press Ctrl+P move your cursor or let your cursor be in 3D window and press F6. A popup will appear - play with the settings there to adjust how much spacing you need.

That is not what I am looking for. The operation you suggested, translates all the islands randomly and fills the entire UV quad with them. What I need is the ability to reduce the spaces between only a few selected islands out of the entire set, without changing (drastically) their positions.


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Mark seam on borders only?
It's quite often that I am selecting a bunch of polygons and want to add seams only on the borders of my selection (rather than on every edge that I have selected) any chance to do that?

Choose edge selection mode instead of faces.

Maybe try Select > Select Boundary loop, if that's what do you mean by borders

@MrZak, that was EXACLTY what I was looking for. U wanna write an answer?


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How to make a shortcut for this button?
"Keep UV and edit mode mesh selection in sync"?

Press Ctrl+Alt+U to bring up User Preferences. Then go to the Input tab. Then expand Image, there you'll find UV Editor. Expand that and scroll down to the bottom and click on + Add New button.
In the identifier, input this: wm.context_toggle. Then in the context attribute, input tool_settings.use_uv_select_sync.
Finally select an unused keyboard shortcut. I used ` in this case. Select to Save User Settings so you don't have to do this every time you start Blender.

Worked as a charm, ty.


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Set meshes for each frame of the animation?
When you export a cloth simulation as an alembic file and then import it again, you get a modifier on the cloth mesh called "Mesh sequence cache". The meshes in the sequence are read from file. What I want to know is whether it is possible to set custom meshes into keyframes to get a custom animation with a single mesh?

Have you looked into the Mesh Cache modifier?

Yes and it requires a pre-existing file .abc to work. It exists solely for that purpose. I want to set my own meshes to each frame in the editor.


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Alt+Left mouse to orbit, while "pick with left mouse button" is enabled?
A tough nut I guess. I am trying to make controls similar to Unity and Substance, but I can't make this happen. I can either have Alt+LMB orbiting OR LMB selection. Is there a way to have both?

Trying to do the same, i'm going between unity and blender too much.
I need ALT+Left mouse button got orbit.

It's 2020 and Blender 2.83 allows me to select Edit --> Preferences --> Input --> Mouse --> Emulate 3 Button Mouse and that disables the mouse middle mouse button and I can orbit with Alt+left whilst still selecting with the left button.

Here is a best addon blender sensei download here
In this addon there are much of shortcut and much easy to use.
There are various tutorial in the webpage how to install and use.
Note : In this addon blender will work as a normal but the shortcut and display view change.


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Mark seam's shortcut code?
Blender has a lovely system for creating new shortcuts. Can anyone advise me on the code for the "Mark seams" operation? Bonus points for the button-toggle (one button to mark/unmark).

Two buttons, but you have that on the toolshelf, 'shading/UV' tab. For the shortcut Ctrl+E then choose in the list

You may also assign your own buttons to these operations in the same manner as here: http://blender.stackexchange.com/questions/36894/how-to-assign-a-keyboard-shortcut-for-a-mesh-selection-mode

Paul Gonet deserves a plus because he actually showed hot to create the shortcut (even by just pointing to the solution). U wana post an answer?

Press Ctrl+E and choose "Mark Seam" or "Clear Seam" from the list.
Then, in order to add a shortcut, you can do as explained here: How to assign a keyboard shortcut for a mesh selection mode?

Please aprove my edit to your answer.

Btw, for anyone concerned, there indeed seems to be no way for a one-button solution. You would need separate buttons for mark and clear.

You can also (now?) press ctrl + e then press m on your keyboard

If you are ready to invest a bit more work (Like I did for my Spacemouse Pro), you can also create a Pie Menu with mark and unmark, so you just need to press a key and move the mouse.
https://vimeo.com/103321600
Code you will need is:
pie.operator("mesh.mark_seam", text="Mark Seam", icon='EDGESEL')

pie.operator("mesh.mark_sharp", text="Clear Seam", icon='MESH_CUBE').clear=True

Instead of the sample code with pie.operator_enum...
To register it as an add-on to keep it permanent just use the code below on top of your script
bl_info = {
    "name": "Mark Seam Pie Manu",
    "description": "Edit mode Edge Menu",
    "author": "...",
    "version": (0, 1, 1),
    "blender": (2, 79, 0),
    "location": "3D View",
    "warning": "",
    "wiki_url": "",
    "category": "Pie Menu"
    }

If i understood the question you want to add shortcut for mark seam
In Edit Mode -> Select the Edge and Press Ctrl+E

and how over the mouse and press right click and select Change shortcut

As soon as u click on change shortcut u get a pop-up press a key

I have selected the dot button from left of the keyboard
Now open user preferences and click the save user settings so that next time when you open blender mark seam setting will not disappear.

If you copy the entrance at the userpreferences in input/3DView/Mesh you can add even more than one shortcut for the same action (as i recently learned here). This solution is the most simple one you could get!

In addition to the other answers. what i do is use CTRL + E then mark seam on one edge then for the rest i use SHIFT + R which repeats the last actions. So if you do anything other than selecting the edges like say add another edge loop you need to mark one seam again and then use shift + R to repeat. hope this helps someone, i know this is an old question.


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Export model without materials?
Any way to do it? Or maybe turn materials "off" temporary? The problem I am trying to solve is this: I make a model with different materials only to create a material ID map. If I export it as FBX to Substance Painter, it has several "texture sets" (equal to the number of materials) once loaded in the latter app. That adds an extra step to the workflow: merging maps after export. If I could "turn off" materials before exporting from blender it wold be much easier.
Mind: I obviously can just delete materials before exporting, but I fear that when iterating on some changes I might forget to revert the deleted materials and loose all my data.

In the export options, try exporting as mesh only

DId not find those options for the fbx, what kind of file format do you suggest?

If you try to export, in blender there is a row of options highlighted on the bottom left. Try with only mesh selected over there.

I already did - it still exports the materials.

Okay, if exporting as Wavefront's .obj file there is a check box "Write materials", unchecking which solves the problem. .obj is widely used and will work in my case.

Let's say this is your model:

Export it as Collada(default)(.dae):

Then import your Collada (.dae) file and export it as .fbx:

Results:
You will have an fbx without textures
Hope this helps
NOTE: I am not the creator of the 3D model in the images.

Well, I already posted an answer that works and requires less steps. Btw, my experiments with .dae showed that it preserves material information. Maybe when you re-import it. But still it's just too much stuff to do.


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Set minimum distance between hair particles
I have a mesh with a hair particle system, with mesh objects as hair particles. As you can see in the image below, some of the objects intersect with eachother.

I would like to set a minimum distance between the hair particles so they don't intersect anymore, but I can't find any way to achieve this.

I have tried to do this before, and I don't think it is possible. Would love to have this feature, though, because there are so many potential applications!

If you are making water droplets, I would try using meta balls for the particles. I don't know if it will work, but, it would be good to try it.

It's not for droplets. I want to place trees on a map without them intersecting eachother

related http://blender.stackexchange.com/questions/36892/how-to-use-emitter-for-generating-thick-forest-so-that-trees-would-not-intersect

@lemon definitely related, but a different question.

i had a similar problem a while ago, didn't find any solution nor did I get any suggestions on how to solve/work around this. See my question here: http://blender.stackexchange.com/questions/60587/particle-emitter-is-intersecting-bounding-boxfaces.
Seems like a lot of people wants this option but nobody knows how to solve this issue.

After researching a bit further, it looks like this is not a built-in feature for Blender. Although there are some workarounds to sort of achieve the effect that have been mentioned in the comments, the solution seems to be an add-on:
https://blenderartists.org/forum/showthread.php?233643-Addon-Moleculars-physics
http://pyroevil.com/molecular-script-download/
Here is a quick GIF of me doing particle collision with the add-on (I am on a Mac, so I am using an older version):

This question is very similar:
How to correct collision between particles

authors: Константин Данильченко


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How to get updated vertex coordinates as object moves
mesh = obj.meshes[0]

for index in range(mesh.numPolygons):  # iterate over faces
    polygon = mesh.getPolygon(index)
    polyMesh = polygon.getMesh()
    mat_index = polygon.getMaterialIndex()
    for poly_vert_index in range(polygon.getNumVertex()):
        mesh_vert_index = polygon.getVertexIndex(poly_vert_index)
        vertex = mesh.getVertex(mat_index, mesh_vert_index)
        print("Index ",index," polyIndex ",poly_vert_index," vertex ",mesh_vert_index," coord ",vertex.x)

As i move the object (by applying force) the coordinates of each vertex remain the same, how do i get the updated coordinates as the object moves and rotates. Also how do i get the updated face normals of the moving object?

Visit this link and look at the part on geting global position of a vertex http://q-tutsblog.rf.gd/how-to-create-laser-beam-reflection-in-blender-game-engine/

Reading the mesh provides you with vertex data relative to the object the mesh belongs to = coordinates in Object Space.
As long as you do not deform the mesh this data will remain unchanged.
According to your question you want to get the data in Scene Space. This means it will change when you move or turn the object or one of it's parents.
Positional vectors
You can convert positional vectors from object space to scene space by multiplying them with the object transformation matrix:
positionInSceneSpace = owner.worldTransform * vertex.XYZ

Normal vector
The normal Vector is not a positional vector. It's purpose is to represent a direction rather than a position. Therefore you consider rotation transformation only:
normalInSceneSpace = owner.worldOrientation * vertex.normal

UV.. probably me.. but I've not come across the term 'Scene Space' used in Blender before, as opposed to 'World Space' (..isn't that shared by all scenes?) I could be wrong.. or just pedantic ... ;)


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Change orientation of object while following path in game engine
I am making a shooting gallery game. I have ducks following a circular path. When one of them is hit, i want it to flip on its back but still follow path. I could make two separate actions, one for hit, one for no hit and drive them by frame number in the game engine.
But i was wondering if i can simply apply a rotation to the duck while it is following the path when it is hit. If this is possible, can someone give me some guidance on doing so.

I suggest to use two objects.
Sledge
The base is the sledge that plays the path following animation.
Duck
The Duck is parented to the sledge. When hit it plays the flip-back animation.
As it is parented to the sledge it will still follow the sledge movement.


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F2 addon suddenly doesn't work properly anymore
I was using the F2 addon, but all of the sudden, it just spit out an error, anytime I have two Edge loops, I want to connect with the F key. The error is the following:

Did you try removing doubles? There's a possibility that this is caused because of multiple vertices at the same position.

The key error suggests an issue with loop[uv_layer] where uv_layer is the key.  Is there a chance it's None.  Does mesh have a UVMap?  Try the help button on the addons expanded info panel in prefs.


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Floor constraint with bumps?
I am making an animation with a car and was wondering if there was a way to integrate bumps into the floor constraint, so that the wheels would automatically go over the bumps

Yes, you can do that, by creating a floor marker and using a shrinkwrap constraint to raise it up the level of any bumps:

The wheel's armature has a wheel parent, an axle, and a floor bone.  Both the axle and the floor are parented to the wheel parent.
The floor bone is raised to the level of the mesh by a shrinkwrap constraint, as pictured.  (Not lowered, but you can build that in with a second constraint if you want.)  The axle has a floor constraint (with offset) targeting the floor bone.  As the wheel parent moves over a bump, the floor bone raises to the level of the bump, which raises the floored axle bone.

I mean, wow. That should do it. I honestly completely forgot about this post because it was made 3 whole years ago. I appreciate the help though.

@Soper Frazzy Ehhh, it was in the list of unsolved, and I couldn't find an answer to my own problem, so.... :)


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how can I show a texture over my bump texture?
So I've got a bump node setup using one black and white texture.
but now I need to show my blue texture over my bump texture.
How do I do this?

The node setup you have shown looks like it should work fine.  I believe your problem is that you are multiplying the bump map by 0.000, effectively disabling it.  Try increasing the value of the Multiply node.
If the Multiply node is just supposed to control the strength, you don't need it at all, you can just adjust the Strength slider on the Bump Map node.  You can also delete the Invert Color node and use the Invert checkbox on the Bump Map node.
Just select the Invert node and the Math Multiply node and hit Ctrl+X to delete them and keep the other nodes connected.  Then adjust the Strength and select Invert on the Bump Map node itself.

You might want to try plugging the bump map into the displacement input of the material output.


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Whats the best way to render a 360 video in blender?
So I made a 360 degree video in blender but the quality is terrible.
Does anyone know how to make my video look more HD?

Coud you show your current settings?

Terrible in what way? You probably need to up the resolution? For 360 you need at least 4096x2048 if you are rendering equirectangular. Problem with this resolution is that it takes forever to render an animation, so a lot of optimization will be necessary to keep your render times in check.

I wonder if it'd be faster if we rendered 4 sides and then merged them into one, this way we can have it better optimized since only one side is being rendered at a time instead of loading whole scene at once


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Ovelayed images show transparent in compositor
I am adding some overlay images in the compositor.
But when I add the images it appears to be transparent.

Why is my image appearing like this?

Maybe you ment to use a color MIX node instead of the ADD mode?`

That does not work, because when using a mix node I must reduce the value of the one image to increase the value of the other. (thanks for your suggestion though)

FIXED I must use an "Alpha over node!"

FIXED I must use an "Alpha over node!"


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Moving an animation from 1 rig to another in a separate Blender file
I got two exact rigs in 2 separate blender files.
I need to move the animation from the rig in the one file to the same rig in the next file.
I have tried appending, linking, and just Ctrl+Copy Ctrl+Past; but every time the location and rotation comes in wrong.
I have been working on this project for over a year now... Please help!
Thanks.

Not sure this is exactly what you're asking but only today I had reason to copy animation keyframes from one length of spiral party ribbon to another and which was not identical mesh to the first.
This copy/paste method should also work in you case so I'll outline what was done firstly, then come back to your situation.
Both ribbons were required to be bouncing up and down, expanding and contracting etc. as party ribbons do.
The new ribbon was not animated so it was given a dummy 'location' keyframe at frame 1 in order to have it appear in the Dopesheet.
The original ribbon's keyframes were then copy/pasted into the new ribbon's strip.  (CTL-C/CTL-V)
That involved the timeline cursor being set to a frame a little past it's location keyframe at frame 1. I chose frame 11.
The 2nd model's title in the Dopesheet needed highliting for the paste operation's destination.
The 2nd model's strip(s) accepted the animations and whatsmore they worked.  The original model however also got a copy of the same keyframes and that's when it's 'wheels fell off'!
The work around was to deselect every new keyframe in the 2nd streamer's strips and what was left highlited were then deleted.
That cleared out the trouble makers affecting the first streamer and it reverted to it's old self and worked fine.
Now back to your question -
If you append not just your model but the entire scene into the 2nd Blend file as I do, that might help, but it's only a guess.  What have you got to lose?
When you copy/paste the first model into the 2nd file's FIRST scene, and into a spare layer, it's animations keyframes should appear in the Dopesheet.
These should then be copiable into the second model's strips as I've outlined above.
Recall that I inserted a dummy "Location" keyframe for the 2nd model just so it would appear in the Dope sheet.  What surprised me was that when the 2nd model (ribbon) accepted the copied keyframes, it didn't take up the identical location of the first!
It remained where it was and started animating from it's own location.  Was that because of the "location" keyframe at frame 1 ?
If your 2nd model has no animation it would also require at least one keyframe to get it appearing in the dopesheet.
Given that you're having trouble with the rotation and location, try inserting keyframes at frame 1 for all three, rotation, location and scaling.
Move the timeline to say - frame 11 and copy paste all the original model's keyframes into the 2nd model's strip.  Left click on the 2nd model's overall 'action' strip to highlite it and do the paste. (CTL-V)
The keyframes will copy over, and in your case the troublesome extra copy in the original model's strips wouldn't matter because you'd be deleting that model anyway.  If not do as I did to eliminate the problem.
At present I don't have time to test this with bone animation but I would imagine the mechanics would be the same.
If you try this, let us know how you get on...

Append the Action data block from the first file into the second file, then set the Action in the Action Editor.  There's no need to copy and paste.  If the rigs really are identical, connecting the appended Action should be all you need.
If location and rotation comes in wrong, I'd check the position of your Armature in Object Mode-- could be that you have values on it in one file or the other.


text:
Black turns transparent in Blender texture
My texture has some black text (on right side of picture,) and also a transparent background. But the text also is transparent?!? Plus I must keep the text black.
Picture:
Please help.

try removing that "use alpha" setting...? black is interpreted as transparency if such thing is enabled...

Try plugging the alpha output to the factor input of the mix shader, and swap shaders if necessary.

Plug the "Alpha" output in the Image Texture node to the "Factor" input in the Mix Shader node, and swap diffuse shaders if necessary.

Thanks for you help Tooniis!
I added the alpha in the mix node. And then switched the other two around.

You can put this as an update in your question, and please click that green check mark under the vote count on my answer it means that this answer is what you are looking for.


text:
Green lantern like construct material in Blender
How do I create a Green lantern like construct material  in Blender.
Hear are some reference images.

This is my attempt but It's not exactly what I'm looking for. For one think I'll like a a bit of a glow.

If you can help please let me know.

Yeah for a glow you'll need to use the compositor.


text:
How can I break apart a mountain in Blender?
I need the top of a mountain to be smashed into pieces when somethings falls and smashes into it. I made the mountain itself using the ANT landscape add-on in blender.

I tried to break it apart using the cell fracture add-on but I can't figure it out.
Can someone please let me know how I can use the cell fracture add-on in this situation or if there is a better way to go about this.

you can break it by adding a subdivision surface modifier, and setting the number of subdivisions to something like 999. I speak for experience here - doing that will break a lot more than just a mountain :)

Probably not the type of "break" that you meant though -

Fracture Modifier Tutorials

@X-27 Judging by his face count in his image, 999 subdivisions would give him 126770850718706813293168277908033756265824209076123280560738922786616981751638568204483057181637039793045211185613800702130163640063694254419394210691141011464980377514796553962760515496529245544788249736078598337175620714185159712052430094302580924736974751949695012644896212779048979557835355725688542830106164100855189858960867308150658308135467133472948683349651620910770875279208689988298203933364693666280766955074951098230656823150801892287188873068442994794080756636750536...

@X-27 ...3820386044930607426579493532969082710800456263125250159029860188017567740005874571391254285418453986 565557715164033962007855104 (44166*4^999) faces. ;-)

@X-27 I don't want my blender to break :), I just need the mountain top to be smashed.

@ScottMilner Yep! that would absolutely break it :)

You could try out the Fracture Modifier Build
from here... http://df-vfx.de/fracturemodifier/
or here http://graphicall.org/1148
which is a separate blender build.
I closed the bottom of the landscape with a face, then I prefractured this with a helper object and Voronoi + Boolean. After that i set up some easily breakable constraints and triggering, and added a ground plane.
Simulation looks like this:

If you have further questions, please post either here on stackexchange or here :
https://blenderartists.org/forum/showthread.php?343637-Custom-Build-Blender-Fracture-Modifier
The Blend link: (will only work with the Fracture Modifier Build)

Will downloading this blender build cause any trouble with the normal blender? I'm a bit nervous about this. Is there any way that I can do this with out a new blender build?

well, you could still try to close the shape with a bottom face and apply cell fracture, but then you will see cracks all over the place, have many objects etc. You could also try to create a folder named "config" right under the 2.78 folder of your unzipped Fracture Modifier Build. This way ALL settings, addons, startup blend will be looked up in this folder first and created there if necessary. This is a completely isolated build then. But note, if you delete this build again including its config folder, the settings for this build are gone, too. FM build is compatible to 2.78c release.


text:
MakeHuman to Blender texture problem
I create a 3d character using MakeHuman v1.1. Later, I exported to Blender using Collada format. I have a problem with the textures. The next picture show us the problem. The white part in the skin is the problem. If I reimport using the same format the problem is not present.

I think that not is a UV mapping problem since that is imported from MakeHuman and Blender is using the default mapping.

An easy fix would be to export in the blender exchange format. All textures should then be displayed correctly.

Sorry but I try to not reimport anything.

@user3477118, the best way to work with blender and makehuman  is *.mhx format.

authors: عبدالله عبود


text:
Adding multiple green screenplates into an animated 3D environment
This is my first question here and I am relatively new to Blender...
I am creating a music video of band members videoed in a green screen environment to be placed on an animated 3d stage.
I will record each member separately, but I wish to be able to see all separate recordings in the one screen shot of the whole stage.  I will also have close ups of each member but I am ok with that.
My problems are as follows and I would like to know how to fix this:
When I render a shot my render comes out the size of my green screen frame size and not the 3d camera view point of the stage.
Q 1
Why can't I place my green screen recording onto the stage and the end result view be larger than the green screen frame size?
Q2
How do I include the footage from two green screen recordings into the one render scene?  I am hoping that once I solve Question 1, Question 2 might be self evident.
I look forward to your assistance.

Your best bet would be to add the green screen video as a video texture on a plane object. You would need to create a black and white alpha mask clip as well to drive the transparency on the material node. This way you can have a plane object for each person in the scene and place them in the scene as needed.
Here's a test scene I just put together using this Minion green screen footage here: https://www.youtube.com/watch?v=QjN0BsUqeb4
I used blender's compositor to key out the green screen and create a black and white alpha matte video file (it's not a perfect key, but good enough for this demo):

Then I imported the green screen video use the Import Image as Plane feature. I find setting the image material to Emission works better than Diffuse in this scenario.
Then I set up the material to use the BW video file as the factor input for the Mix node that is mixing a transparent shader and the colour emission shader.

Final Output from Scene:

I should also mention that another advantage of handling the transparency via the Material as opposed to doing it in the Compositor after rendering is that you can see the character properly in the viewport when setting up your scene. This is very helpful in the pre-rendering stage for scene development.


text:
"Funnel" or "perspective" scaling?
Say I have a square and I want to make it into a trapezoid, I then scale down one of it's sides right?

Now what if instead of a square I have a very complex square-like object with lots of subdivisions? Is there any way to perform a similar operation? The one that will change the overall shape of the complex square-like object into a trapezoid-like object?

In Photoshop, when usint freeform transform tool this type of scaling is called "Perspective".

In your illustration of the transformation of the complex shape, I don't see a trapezoidal transformation; rather, it looks to me like the complex object appears to have undergone a scaling down on the entire top-to-bottom axis, and a scaling up on the entire right-to-left axix.

dude, add the lion into Photoshot, press Ctrl+T and then right click and choose "Perspective". Then scale down the bottom side like in my first picture (only reverse) and u will get this shape. My example is a bad one I agree.

Blender is not a photo editing software nor some 2D graphics tool, if you want to transform something you select the corresponding geometry and modify it. In this case I'd select the top edge of the square and scale it down.

@DuarteFarrajotaRamos unless you know 100% that Blender cannot do what I need it to do (which your answer does not imply), I can see no point in your answer. Just a waste of memmory.

Ok, what I needed was Mesh Deform modifier.

https://docs.blender.org/manual/ko/dev/modeling/modifiers/deform/mesh_deform.html


text:
reference image won't show
I was using image references to create a character however after pressing some keys on my keyboard, which activated a short cut, when i attempted to go into front view to see my reference u=image, it appeared to have disappeared. As i was following a tutorial and therefore was doing it as a learning exercise i was willing to restart the project again, i started a new file. However once i re entered the reference images it still would not appear on my front view (I did set the axis' correctly)
If anyone knows of anything that could help that would be most appreciated,
Thank you,
Nura

If it disappeared after you entered another preset orthographic view then it means you set up axes incorrect (in background image options).


text:
How to make brush size lock in texture paint
I need to lock brush size in texture paint mode (not relative to zoom), but it's aviavle only in scupt mode

How to make it happen in texture paint mode?

With Blender 2.79.
By default, with a 'tiled' brush mapping, not only the brush texture size is changed with zooming, but the brush texture is also offset when changing the angle of view.

However, the brush mapping can be changed to '3D' to prevent resulting in texture painting interference by view resize/change.

From Blender 2.79 documentation:

The 3D option allows the brush to take full advantage of procedural
  textures. This mode uses vertex coordinates rather than the brush
  location to determine what area of the texture to use.

Note that it works perfectly with image texture as well.

Very nice explaination but could you please update it for 2.80.


text:
How to simulate tablet pressure is sculpt mode?
I don't have tablet, but I need to make Blender change brush radius dynamicly, depending on mouse speed. Is there any way to do this? Maybe some third-party software that able to do this?
I'm already tried this addon but that's not exactly what I need (and also it doesn't work)

Do you need it in the sculpt- or texture paint-mode?

I need this in sculpt mode, and this addon actually created to be working in sculpt mode. And i'm not that much about Python to redact it


text:
How to disable x-ray for annotations (grease pencil) in 2.8?
Is it even possible in 2.8? In 2.7 we had such ability, but now, when grease pencil and annotations are separate things, xray possible disable only for grease pencil, but not for annotations

@RBlongus2us
You must use single or double quotation marks: "Annotations" or 'Annotations'.
"Annotations" as well as "True" and "False" have to be written with a capital first letter (but not the entire word!) so that Blender and Python can recognize it:

The annotation layers are numbered beginning with "0" at the bottom of the layer list. This index is used in the square brackets, so that you for example switch off the x-ray visibility of the first and the fourth grease pencil layer (indices "0" and "3") in the last two images above with the commands:
bpy.data.grease_pencils['Annotations'].layers[0].show_in_front = False

bpy.data.grease_pencils['Annotations'].layers[3].show_in_front = False

'Annotations' is the name of your annotation data block. As long as you don't manually edit the name, the next annotation data block created would have the name 'Annotation.001' and the corresponding python command for switching it's first layer's x-ray display off would be:
bpy.data.grease_pencils['Annotations.001'].layers[0].show_in_front = False


text:
How to properly create hollow text letter suitable for 3D print?
I am doing this project, where the objective is to print some hollow letters. I get to the following result with the spets that I took, where the objective is to make the letter 5 mm thick, with walls and bottom being 1 mm thick.
Steps I took:

I wrote a specific letter, resized it to proper size.
Then I apply extrude (5 mm) and set fill to BACK in the type settings.
I added Modifier (Solidify), with thickness 1 mm to the edges. Checked boxed: flip normals, even thickness and fill rim. The result so far was this.

Then i converted text to curves and then to mesh. I mirror the letter for printing.
I get a lot of intections (intersect face) and overhang face errors as seen below.

What can I do to fix this and is there another way to get the same result that I don't know of?

Welcome to the site. Was the scaling in the step 1 done in Object mode ? And if yes was it applied with Ctrl+A ? Also did you set up Offset in Object Data settings of the text object ? (this could cause these intersections)

Did you remove doubles as last step of the process? Font files are know to often be badly optimized, with lots of overlapping geometry and duplicated vertex. Also all the steps afterwards are prone creating duplicates and overlaps

@Duarte Farrajota Ramos I did but nothing changes unfortunatelly.

Well then nothing like a good old manual fixing

Are you making the letter hollow to reduce print material? I think some slicers have a setting for that though. If that is the case it may not be critical to be over picky about the internal dimensions of the hollowed volume. If this is your actual objective, consider placing a cube in the midst of your 'solid' text, and editing (stretching) out the vertices to create an internal cavity. Use loop cuts (ctrl-r) on the cube in edit mode to add more vertexes as you see fit. And just move them around from a TOP ortho view until it creates a substantial vacancy where material would otherwise print.
This is a quick fix and I use it all the time for test prints on my photon. Don't forget to make a drain hole if you print with resin.
However if this is a classroom assignment, then you will probably want to create an exact absence of the letter's internal shape. You might consider duplicating the letter on top of itself - and then scaling it around a bit until you can subtract (boolean modifier) a smaller version from the original (right inside of it). Doing that may be difficult depending on the shape of the letter however ~ since the scale factor will be relative.
If you don't care if the letter has surface features - then you could simply take the outline of the letter and attempt an inset of it (shortcut i) in edit mode. Extrude both (the original outline and the inset) and then perform the same boolean I mentioned above. Subtract the extruded-inset version form the original larger version. You should get a near perfect, although flat on it's surfaces, hollow letter. Bet you're going to do a little sub modeling though.
Good luck with your project.

To create a hollow letter :

create a new project and remove the cube
Add a text object
press TAB to enter Edit mode
change the text to the letter your want
press TAB to exit Edit Mode
press ALT + C and select "Mesh from curve/meta/surf/text"
press TAB to enter Edit mode
press A to select all vertices
press E to extrude to the alf of the final letter depth
press Shift + S and select "Cursor to selected"
press X to delete faces
press TAB to exit edit mode
select menu "Object / Transform / Origin to 3D cursor"
add a solidify modifier
change the thickness
apply the solidify modifier
press TAB to enter edit mode
change the view to Front Ortho (5 1)
press Z to change to Wireframe display
press B and draw a border to select faces on the top of your letter

press X and select "Faces"
press Z to come back to Solid display
press TAB to exit Edit mode
add a mirror modifier
select the proper option X/Y/Z (unselect X and select Z)
apply the mirror modifier

I have seen some tutorials for cleaning up the mesh on converted text by using the Remesh modifier to create an even grid mesh.  Might be worth a try at one of the earlier stages after converting the font.  Be sure to uncheck "Remove disconnected parts" and play with the octree depth to see if you can get something workable.
Here is a vid showing its use on a single character. https://www.youtube.com/watch?v=PEt07reVhJ0
Added:
I just ran across this video https://youtu.be/QxDOhxjdFOs
The first part of it shows a way to make text with very clean geometry.
Hopefully one if these ideas will help with your project.


text:
how to change camera view of a player?
You guys know that when you play games, you can see whats happening around you right?how do you change the camera view so that your camera is on the head of the character and not behind the character?

He asked how to change the view not how to rotate the camera (the mentioned answer). Regardless of that the question needs some clarification: Do you want to switch (or transit) in-game from third-person-view to first-person-view? Or do you want to know where to place the camera in Blender (before starting the game) to get the first-person-view.

You have to parent the camera to the player object by pressing Ctrl+P,
then move the camera where you want it by pressing G.


text:
Animation Nodes: Ability to create mesh and assign UV coordinates?
So far, working on the 1.0/master branch of Animation Nodes, I've been having a rather hard time creating procedural mesh data, and I eventually ended up just writing a python script to create the data that I wanted output - but I've just come to a barrier that would actually prohibit my next phase of the design I'm currently working on: I want to assign procedural UV coordinates to the procedural mesh that I've just created. My script currently outputs (VectorList, PolygonIndicesList) data for a Mesh Data node, and I am assigning that MeshData to an Object in the scene. I think that it is here where I seem to be lacking the options for UV data...?
I guess this question is two part:

Is there currently an efficient workflow for generating procedural meshes in Animation Nodes?
Is there any way to create procedural UV coordinates for that same mesh?

I was also having a hard time finding documentation or examples of the above, so if there are any currently available resources on this topic, I would really appreciate some links covering the topic.
Thanks! :D

While animation nodes focus on animating data, sverchok has it's main focus on generating mesh data. The uv data can be found in obj.data.uv_layers['UVMap'].data[x].uv - there is one data[x].uv for each face vertex, but I'm not sure on the relationship between each face and the uv data, I only guess polygon[0].vertex[0] == data[0].uv and polygon[0].vertex[1] == data[1].uv...


text:
Any way to create a 360 stereoscopic video for playback in VR?
I have search the web for a solution to my problem, but most of the solutions out there seem to be created for a "fixed" view-angle..
For instance:
http://www.dalaifelinto.com/?p=1009
That would only create a "flat" movie with depth.. but what If I actually want to create a spherical 360 stereoscopic top-down(or side by side) video for playback in VR?
Simply using the above solution and turning on Panoramic->Equirectangular wouldn't do it.. since after all.. the cameras(left and right-eye) has to rotate around the center of the cameras/eyes..

As you might notice.. the problem with only using a Equirectangular is that as soon as the user turns his/her head to any other direction than the direction the cameras was pointing to.. the stereoscopic-effect will "break".. or you will end up with a "cross eye"-effect..
Any ideas of how to solve this.. any tutorials around that you are aware of?
Br,
Inx

You should check http://vrais.io/tutorial and their presentation from the  blender conference. Look at the results yourself by using their app and a cardboard. As written, you need the special blender build for that.

Starting from Blender 2.78, there will be a 'Spherical Stereo' checkbox in the camera panel which does exactly what Sybren has described. It will pivot the stereo camera per pixel to give you always the correct stereo offset for any direction.

Read official release notes for more details.

Great. But with my quick search I found this will be available since Blender 2.78, not 2.76. Release notes

You can download a working pre-release of 2.78 here: http://download.blender.org/release/Blender2.78/

You need to check "Views" under the layers tab for the Stereoscopy section to appear in the camera properties

As far as I know, what you suggest, rotating the camera pair in small steps and stitch them together, is exactly what Blender's Multiview feature does. It doesn't need explicit stitching, as it effectively rotates the camera pair for every rendered pixel.
You can find more info in the Multiview section of the Blender manual. The Camninandes VR demo also doesn't have any issues on the left/right/rear.

This is a really hard problem that nobody has fully solved.
Here's the issue:  Cleanly stitching together a panorama relies on a single-viewpoint constraint.  But with two cameras, it's geometrically impossible to rotate them around, keeping them side by side while maintaining that constraint.  A full solution would require either separate video for every possible viewing angle, or some sort of real-time re-projection based on saved 3D information.
Various compromises are possible.  For example, Google has made a really interesting attempt based on data from their Jump camera rig. Their trick is to treat parallax as a fixed angular shift as a function of distance.  This approach is imperfect at the edges of the display, or when looking up or down, but it's not a bad approximation.
If you're happy with Google's approach, you may be able to render to the same format that their rig records (by using multiple cameras in your scene), and submit the videos to Google for post-processing.
One approach you might try with Blender is to render your video in several concentric spherical shells by setting the near and far clipping distances, and rendering with transparency.  You would then need to create a viewer that superimposes the shells, rotated different amounts in the direction of eye separation, to simulate parallax.

The method in the link you gave actually does render fully stereoscopic 360 panoramas. You get an output of two 360 images as you can see in the third image in your link, one for each eye, and it works in all directions. I've tested this in Google Cardboard.
Here is the official documentation: https://www.blender.org/manual/render/workflows/multiview.html
Here is a GIF of an image pair I rendered as a test. You can clearly see there is a left, right image offset over the full panorama.

If you compare these images carefully, you'll see that the offset is reversed for the objects behind you, and there's no offset at all for objects to your right and left.

I don't follow, you can clearly see that the whole helicopter interior is shifting around you between the images. Here is a photosphere image of only the left view from the above pair to get your bearings in the panorama. The outside scene isn't moving between left and right images as it's so far away that you don't have a 3D effect there. If you do want a 3D effect for far objects you must increase the interocular distance in the Blender settings, resulting in hyperstereo.

The rear window shifts to the left in the same frame that the front window shifts to the right.  That would create reverse parallax when you look behind you.  And the chairs to your sides don't shift left/right - they just become nearer and farther.

Awesome image, by the way!  :-)

Thanks! I think the implementation is correct, it's just hard to intuit how the image pair should look. In the link you can also read the paper this method is based on: Synthetic stereoscopic panoramic images. In my experience it does work correctly in 3D as I've been able to test with Google Cardboard, no reverse parallax or anything. I might set up a more rigorous test scene for further testing.


text:
How do I close the User Preferences window when it is not opened by the window manager?
I am running FreeBSD 10.2 64 bit with fvwm-crystal. In all other cases, just starting a program from an xterm opens a window with buttons. Blender does not open in a window with buttons, which in itself is not a problem. However, when I try to set user preferences, the new window does not have buttons, and I can not close the User Preferences window. I tried "dbus-launch blender" but no difference. I do not see any configuration options for recompiling blender that might make any difference. Any advice would be appreciated. Thanks.

Are you asking how to access blender's preferences without encountering this issue? Or how to get the wm to put buttons on blender?

Do you get the title bar of the window so you can drag it around? Blender should get a normal window with standard close/resize widgets the same as any other program, the same when a new window is created for preferences. I use xfce and can use Alt-F4 to close a window (that's a window manager setting), also right clicking on the title bar of the window gives a menu with a close option. This would be window manager related, you would do better trying fvwm support options, or maybe emailing the freebsd-questions list or forums.freebsd.org

@gandalf3 I would certainly be satisfied with being able to access user preferences without encountering this issue. Although I am curious about why fvwm-crystal is not putting buttons on blender, I sense that that question may be difficult to answer.

@sambler There is no title bar from the window manager. The top of the window contains the names of the sections: Interface, Editing, etc. Using fvwm-crystal's command to close the User Preference window causes Blender to quit. I will certainly look to freebsd or fvwm lists for help if there is no solution within Blender.

I hadn't looked at the cli options for a while - blender has -w to force opening with window borders (default) and -W to force without window borders.

You can open the preferences inside the existing blender window by setting the editor type in the header of any existing area:

As for why blender isn't getting a titlebar from the wm, I have no idea. It works fine for me here on openbox.


text:
Can't see or read commands
I just found Blender.
Is it possible to change the background color.I'm old and it's impossible to read the commands. Any help or hints would be appreciated.
Thank you.
Don

A little more information on exactly what you are trying to do would be nice. I think you are looking for the User Preferences, press Ctrl+Alt+U to open them, and go to Themes

You may also find it useful to change the general size of font.  In Blender User Preferences change the DPI to 108 as indicated above. This will make the font bigger than the default. Suit to your personal needs.


text:
how to connect objects with splines with animation nodes?
I have a group of objects all with keyframed movement. I want to a create splines between the closest objects as they move like this...
https://www.youtube.com/watch?v=k9MvcCXsHHY
I know you can connect particles like this...

but dont know how to do the same effect with a group of objects.

Wouldn't replacing the vertices locations with the object's locations be sufficient? Have you tried that?

could you explain what nodes to use exactly? I am lost when it comes to AN

Add your objects to a group, use the Objects From Group node to get the object, use the Transformation Input node to get the vertices locations.

Would you please write up the solution, post it as an answer, then accept your answer please? (You can answer your own questions). That way others can benefit from the answer and others do not come here trying to answer the question when it is solved. Thank you. :)

Add your objects to a group or a collection. Then get the objects using the Collection Info node or the Objects From Group node. Finally, get their locations using the Object Transforms Input node. We now have the points locations, we use the Find Close Points and Splines From Edges node to create the splines as follows:


text:
What is causing this weird shading effect in rendered view?

Whenever i look at some textures like the one in the pic i get a weird pixelated effect but looking through the camera it looks fine. Does anyone know what causes this

Do you have enough samples? What is the texture? (upload it if you can) What is your full node setup for this texture?

Are you using displacement? Are there enough subdivisions?

it seems to be a problem with everything in the viewport and not a particular texture. I have the samples set at 32 but tried higher and it didnt change anything

It seems to be an issue with backface culling. I turned that on and subdiv+ smooth shading and it seems to have solved the problem.


text:
Can Blender save Rendered image periodically
I usually render still images with very high samples(1000-5000) in cycles render engine.I leave this rendering on my desktop PC overnight.
I was wondering if there is a feature/addon that can save the rendered image every 100 samples or every 30 mins or something of the sort.
So that when I wake up in the morning and there was a power outage during the middle of the render, I still have a render close to the quality I wanted rather than none.

I believe the "save buffers" setting in Render settings > Performance does something like this, however I haven't tested it.

Maybe this answer is useful for you as well.

@gandalf3 I have searched all over the internet for details about that feature nothing comes up.Could you explain more on it.

@binweg unfortunately it doesn't

@Jamesup Unfortunately, after some testing, it appears save buffers does not do what I thought. It caches finished renderlayers to disk (by default in /tmp/blender_<random_hash>/_<scene name>_<renderlayer name>.exr)

james to be sure you recieve this, i do it as comment heer, but its basically the answe i gave in scripted addon : http://adaptivesamples.com/2013/07/22/progressive-animation-render-addon-and-image-stacking/

There is a trick that you can recombine images in post editing with blender.
Then you can combine 10 images or so, (using animated seed settings).
So you render a still image as animation images with lower sample rates and recombine them. it takes a bit of manual work to recombine, render speed is slightly lower (bhv rebuilds between frames). for the rest doable.
in the beginning some people hoped to reduce noise.
or in theory one could use this method to increasingly improve a real animation render if you store the images in different folders (by some scripting).
But you might also check the latest blender builds and the denoiser, unless you do a lot of diamont /glass reflections such a sample settings can be decreased a lot.
There is a addon/script that does this
http://adaptivesamples.com/2013/07/22/progressive-animation-render-addon-and-image-stacking/
Most of all though i recomend to review your render settings, today a fairly reasonable render can be achieved with proper render settings:
https://www.youtube.com/watch?v=8gSyEpt4-60

Although this is a good technique, am afraid it doesn't adequately solve the problem. Hopefully blender implements it soon.

well essentially changing seeds allows to recombine every 100th times sampled image, its the same to add image100+200+300+400 samples as compared to only saving an image 500 samples, there is a little overhead because BHV will be recalculated.. If your rendering a still image, you might render it with sample settings 100 then recombine the frames to one image, there has been a time people did this.
But personally i found it a bit complicated to do (lots of compositor nodes to recombine images (averaging them out), it would solve your problem. but its kinda daunting to do in compositor.

That's what I meant by it not being fully adequate, yes it solves the problem but it involves a lot of work, personally I mostly do still images. I appreciate the help but I wish there was a simpler solution, since this is just to avoid a power outage/computer crash .


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Rigify Rig: What's moving the chest bone?
I was looking at the Rigify rig for how it is solving some problems as I was implementing my own IK rig. But I am not able understand this:
Instance a Human Meta-rig, and generate the Rigify rig (no need for having a character). Hide all layers except the torso. Now, when you rotate the hips or the spine bone, the chest bone moves in world space (but not in local space). The chest bone is a child of the torso bone (which has the cube shape), whose transform doesn't change on rotation of spine or hips bone. Both the chest bone and torso bones also don't have any bone constraints.
What's causing the world space location of chest bone to change on rotation of hips or spine bone?
P.S. The reason I want to understand this is: I have a similar torso design, and I want that the chest bone in my rig also move the same way, so that it remains attached to the body (visually). But in my case, the chest bone actually remains static in world space right now, on rotation of hips/spine bones.
Thanks in advance!

The answer is so much simpler than what I was thinking: You can set "At:" field in the custom shape options for a bones. The bone itself doesn't follow the body, just the custom shape does.


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Cycles: How do I exclude the Environment Texture from reflections?
In a Cycles scene I have an equirectangular image serving as an Environment Texture background (set in the World settings).
I have a glossy object being partially lit by the Environment Texture, as well as getting reflections from it.
Is there a way I can exclude the Environment Texture from affecting the glossy object completely? I want the image as background wallpaper only. The glossy object should be affected by other objects and lights within the scene: everything except the Environment Texture.

You could use Is Glossy Ray and a mix node in your environment material, but it might look weird..

Cheers ChrisH, this might be an idea I'll have to go with, but I was hoping for an object/material-based solution rather than an Environment Texture-based one. Your idea will affect all glossy objects: I was hoping to apply it to just one, or just selected objects (which had me looking at the compositor for ideas, but nothing's coming to me).That said, I'm sure I can work with it :)

Ok, you could do it with an material index and working with the passes in the comp. (It's 1am here, so this might not be the best solution [but it's came to mind] or description ..).
So by using a compositing node setup similar to this: link you could accomplish it on a single material-basis (I don't think it's possible in the material).
The nodes in the blue box is based on the "default combining" link, and you might not need all of it (dep. on the material and scene).

The nodes in the purple box is the ones affecting the reflection/glossy, the middle mix node just replaces it with blue, so that's the node you want to edit to change the the. (The greater than-node just singles out the environment [which is black in that pass]).
The nodes in the green box combines the separated parts with the original image based on material index.
You can download the .blend here: https://drive.google.com/file/d/0B88eAnH_kxSrejM5NEF6YW5mY28/view
I hope that's sort of clear (It's not that complicated, just a bit messy..)

Holy crap... I have a bag of cables and phone covers that looks exactly like this node setup... :) Thanks Chris: Material Index! I think that's the key! Yay!

@Oroboros, I asked the same question and I think I've just found a way to achieve a perfect result without having to use the compositor or doing any kind of node setup. It's a little trick with two additional layers and an additional mesh.

Put the object that you don't want to be affected by the Environment Texture onto a new Layer.
On yet another new Layer, create a Sphere which is big enough to enclose your object and your whole lighting setup. (In other words, you put your whole scene inside a big mesh.)
Add a Holdout material to the Sphere.
Under Render Layers, exclude the Layer of the Sphere for all Layers except the one that holds your object that you want to hide from the World.

This way the Sphere will block all the rays coming from the World to your object, but since every other layers are excluded, it won't affect any other parts of your model.

Finally, select the Sphere, and under Object > Cycles Settings, turn off Camera, so it won't be visible on your rendering.

I hope this helped.
Edit: In case you'd like only the world's texture not to show on your object and miss its lightness that gets blocked by the sphere, you can create a slightly smaller sphere inside your original one, give it an emission shader so it can nicely illuminate your object with the amount of light that it would receive from the World normally. Make it smooth, don't forget to hide it from the camera, and one more thing: recalculate its normals inside.

Hmm... I've always wondered what the Holdout node was for. Thanks @tom, I'll give it a try soon (moving house this week, kinda busy :)

This is a little late, but the answer to this question fixed the problem beautifully. Simply turn off the World's Ray Visibility to everything except the camera!


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Equirectangular skyboxes: Tips for avoiding pixellation?
I'm creating an artificial HDRI image with Blender:Cycles- just creating a landscape, lighting it, equirectangular projection, sorted.
When I use the HDRI as a background for new scenes the image seems very pixelly.
I'm rendering the scene as a 4096 x 2048 image, with 40-50 samples per ray. Obviously, this isn't enough detail. But what is the determining factor for a high quality HDRI: more pixels, or better quality pixels? Is there a formula I can use to get me a useful skybox?

4096 x 2048 should be adequate resolution, but keep in mind that the focal length of the camera you use in the second scene will make a big difference.
If your second scenes' camera focal length is high, 50-200mm, it is the same as opening up your equirectangular render in photoshop and zooming in a lot. Generally, a real HDR equirectangular image photographed in the real world will be 4k-12k in width. The 4K is best for reflections and lighting and the 12k might have some use as a seen sky in the 3D render, however, backplates, which are photographs taken at the same time at the same place using a different focal length (not a fisheye for panoramas, but more like a standard FOV (35mm-85mm) are often used to replace the environment image render. That image is then lined up to the rendercam (or should I say, the rendercam is aligned to the image) and it is composited in behind the CG elements, replacing the HDRI 'sky'.  If you wanted to do that without taking a separate photograph, your equirectangular environment map would have to be above 20k (generally speaking).
tl;dr  10-35mm blender camera settings should work fine with a 4k image if rendered out at 1080p.


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Cloth particles: Seeking workflow
I'm trying to make a stream of money (bills) flow into a toilet.
A metaphor for our times :/
I've created several low poly bills and grouped them for a particle system. I've created a particle system and have the bills streaming out. I can get the bills to collide with the toilet: some go in, some go out, that's fine. But the bills are stiff, do weird things when they collide with walls, and they all rotate/move from their object origin rather than collide with corners/edges of the bill. They stick in the floor upright from the origin: they rarely lie down :/
I don't know how to apply the cloth simulator to either the paper objects or the emitter.
File here: https://www.dropbox.com/s/sfr5pxfgn8uo681/toilet.7z?dl=0

I feel like this could be achieved using a cloth sim and wind. You may not need them to be particles.

@Mentalist : If I did that, how would I create a constant flow of cash? Wouldn't 1000 individual bill objects being blown around be more taxing on the comp than a particle system?

Maybe. In these cases it's best to do some rough tests and see which method seems most effective. There is a way to direct particles with forces, and I was looking for the tutorial vid for that. I haven't been able to find it, but I did find another one that looks very relevant to your project. Haven't watched this yet, but in case it helps: How to animate realistic falling leaves in Blender.

Found it! This is the tutorial I was first thinking might help you. "Curve Guide Force Field" is what it's called. It can help you steer all of those bills right into the toilet if you want. ;-)

@Mentalist: I have seen a couple of tutes on particle flow direction using curves. Directionality isn't what I'm after. Cloth simulation acting on particles is the key. The linked tute, while handy, doesn't address either cloth sim, or multiple cloth objects being directed by curves. It's the 'clothiness' I need to apply to my particles, not a particle path.

I wonder if this would be of any help: http://blender.stackexchange.com/questions/17707/cloth-simulated-object-particles-dont-simulate-when-start-and-end-emission-fram

Unfortunately not. If @gandalf3 couldn't dig up an answer the situation seems hopeless :)

I've tried several ways to try and combine physics systems to get around this problem, and none have been successful. I can get cloth simulation happening. I just can't get cloth PARTICLES happening.
I can get Soft body physics happening instead of cloth sim., but the bills don't want to lie down.
I'm still clueless on how to fix this, and I'm not sure if it can be solved at Blender's current stage of development.

With the cloth simulation, you want to select your dollar bill object and go to physics tab; it's in the Properties window under the Outliner by default, same window you go to for your particle systems. The icon is a bouncing ball. If you can't see it, over over the panel and scroll until it's in sight, or enlarge the window. Hit the cloth button. You're going to want to play around with the stiffness setting in particular. You don't want it to act like a dollar-printed hankie. Once you have setting to work with, you'll need to let it run it's simulation. You'll probably do this several times until you get something you like. After you're finally satisfied, bake all your dynamics.
Go back to your particle system; make sure you have gravity on. Mess with the weight values; your money could just be too light. Finally, apply the bill's orientation so that the origin is in the middle of the bill, and it lays flat on the floor by default. That part should help with the standing problem, at least.

I suggest you do everything you just said on the .blend file I supplied. I have 40kg bills that won't lie down. Often they just jiggle around, on an edge or on a corner. Most of them ricochet off toilet edges. The default orientation of all bills is flush with the floor. Nice try, but this hasn't solved my problem.


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Can't get 'true white' video output
I'm doing a short credits sequence (blend file below), where a few alpha UV materials are overlaid, lit with a single sun lamp.
When I render out the sequence, I can't get a good ol' 8-bit white from settings that I think should get me white. If I export a frame and bring it into Photoshop I get F6F6F6 (246,246,246).

If I increase the sun power I start blasting out the logo colours. Increasing ambient light blasts out shadows. Any tips here?
Blend file: https://www.dropbox.com/s/gklakgma0je92xk/flop3.blend?dl=0

make your white material shadless if you are using blender internal, or set it to emission if using cycles. You could also increase the intensity of the material.

This is a bad idea if the issue is (unclear in original question) the result is from an encoded video. The correct approach would be to attempt and diagnose whether the encode or the decode or both was mangled. Much to the confusion of many, a codec should deliver a near 1:1 with RGB values, quantization details aside. Not that your solution is necessarily wrong, but that the original question is lacking on context.

@X-27: Thanks, but I probably won't do the emission idea. I need a shadow to play across the white background, and an emitting object won't receive a very good shadow.

Your render inside Blender is not pure white.
After rendering clic on the white part of your render in the UV/imge editor, watch the values in the bottom part, R 0.92, G 0.92, B 0.92.
You just need pure texture color and lighting, it's too hazardous to try setting the right orientation and strength of a sun to have perfect texture color. You lose some light during ray casting.
You want two things to compose in post processing:

the animation of the logo and the text with the correct RGB values (no need of light for that).
the shadows themselves (need light or tricks that I don't know).

Make a scene without light, and replace the diffuse shaders by emission ones. Now you have the real textures colors, same for the white background. Bonus: you can set the samples to 10 or 20 it's enough
Make a second scene with only the sun, the white background and the text for the shadows. Background and text must have diffuse shader this time. On the render layer panel, under passes activate shadow. Render the frames that matter for the Shadows.
Plug the shadow passe in the fac of a color mix node, put the animation of the logo and text in the second image slot of the mix node, the first one is the color of your shadows.

Thanks Mareck. Interesting idea, but the problem I have with it is that this is a work-around, not a workflow. A diffuse white material lit with a sun lamp on 5 should show a white (or super-white) value. I suspect the problem is related to alpha values. Even though I have three overlapping textures, two of which have transparent values in 8-bit space, might not actually be treated as pure transparent alpha values with Blender. Blender might be converting 8-bit transparency into 16 bit, and that might result in rounding errors for transparent output, darkening lower layers.

Have a try, delete all except the sun and camera, add a fresh new plan, set a diffuse pure white, hit render.
Exactly the same values, so it's not the alpha chanel.
I continue to think you workflow isn't well suited for what you want.


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How to make Volumetric Scatter fade adjustable
In Cycles, I'd like to create a misty torus. Create torus, Volume Scatter note into the Volume Material Output node. Done.
But I'd like to be able to adjust the density of the scatter with respect to surface proximity. So the closer the scatter effect gets to the surface of the object, the more transparent or "less dense' it becomes.
Any suggestions? I'd like this to be material-specific. I could do this in the compositor, but blurring introduces other problems.

Im thinking you start with a cube, then add a gradient texture node in combination with the volumetrics so it starts dense on one side, then clear on the other. Then subdivide the cube and use a deform modifier to bend it into a cylinder, then use another modifier to bend the cylinder into a torus.

An alternative solution to the 'pure' mathematical solution (https://blender.stackexchange.com/a/70340/29586) is to use the Point Density texture node to convert a circular mesh into a density as follows (using a mesh created from a BezierCircle) :

The Multiply and Power nodes can again be used to manipulate the scale and fuzziness of the generated torus.
This has the added advantage that you can manipulate the source mesh as desired :

Note, this method may be less efficient than the pure mathematical approach described in the previous answer due to the use of the Point Density node. It will also be dependent on the number of vertices in the source mesh and the resolution of the Point Density (lower values will produce less accurate results). However, it is more versatile since the source mesh can be easily manipulated.
Blend file attached.

OMFG! Depending on render times, this might do the trick too, but again, this is black magic beyond mere mortal ken. Cheers Rich!

:-) Glad to help. Render performance shouldn't be bad providing you don't go too mad with the number of vertices. This method would be preferble to the pure maths solution  simply because it gives you much more control to manipulate the shape.  Also, keep the 'domain' mesh as small as you can without clipping the volumetrics - any rays passing through the volumetric material will have a high cost - and don't forget to 'apply scale' if you resize it. Play around with the Multiply and Power values - or replace the Power node with a Color Ramp if you prefer to vary it that way.

There seems to be an error in my calculations. I think I will manage to review them later.
As Ibalazscs pointed out, you can control volume with the existing math nodes and procedural textures.
I will setup a mathematic procedural torus to use as density. This will not be affected by the geometry, sadly, but will work as a substitute solution.

To control the density of a volume, we can connect a texture or other value node to the density input of the Volume Scatter Node.

Starting with a two dimensional equation, let's control the volume of a cylinder with a colorramp or RGBcurve.

Here is the relatively simple mathematical basis. We need the equation of a circle.
x**2 + y**2 = radius**2
radius = (x**2 + y**2)**0.5

This will result in values from 0 to 1, starting from the center of the XY circle to any point on the circle.
Translated into a node setup, we have to use the Converter>Math nodes.

Connect the last node to a colorramp and we can see the effect on a 3D object in material or rendered mode.

The complete node setup looks like this.

I use a multiply node before the RGB curves to "scale" the circle. The RGB curves modify the density from the center of the circle to the rim. I have set them to the various examples in the beginning. The multiply node after the RGB curves raise the upper density limit. Close to zero (transparent) values will stay relatively unaffected, values close to 1 or higher will become more dense.
The position attribute of the Geometry node holds the XYZ coordinates. The separate RGB node extracts the three channels.
Important: The position attribute is in world coordinates. Use the Object Info > Location attribute if you move your object.
Creating the torus

Add a cube. This will function as the volume domain of the torus.
Use the existing node tree of the circle calculation nodes.
Add a subtract node to the chain. This will shift the value of zero along circles of different size. We will connect the Major Radius of the torus to the subtrahend. The add an absolute node. We want the values around 0 (our major radius) to fade out towards the center and towards infinity.

We want to control the density using values from 0 to 1 ranging from the major radius to the (major + minor) radius.
The value of the major radius in XY is currently 0.

We are going to use the circle node setup again with the existing XY circle output and the Z axis. After the last subtract node, paste the circle nodes (pow2, pow2, add, sqare root) and connect the subtract node to the first pow2. Connect the extracted Z value (B output of the separate RGB node) to the second pow2. The result is a circle with a major radius of 1. The values at the major radius are at 0. Values moving away from the major radius range to infinity, the distance from the major radius. We need it the other way around.
Negate the value (multiply with -1), now we have values from 0 to -infinity. Add a value with an add node. The second input of the add node is the minor radius. Clamp this value. We now have a range of 0 to 1 from the outer rim of the torus to the inner circle.
Connect this to the RGB curves.

Make sure your domain object is large enough.If you want to add a shader to the outer surface, add a torus with correspoing major and minor radius. In my case

A lot of interesting ideas, altough - so far - the end result does not look as "volumetric" as in Rich's answer, the edges are too visible. But definitely worth an upvote.

I added a surface shader to demonstrate that the volumetric torus is easily recreated as a surface. His answer is better, mine just has some maths.

Oh, I see. I wondered why some intermediate results are better than the final one :)

Thanks Leander. A lot of very good node-fu information on this response page. Thanks for helping out!

Varying the density based on the proximity to the surface of the mesh is tricky - and requires use of complicated OSL shaders to probe out the nearby surface of the mesh. A much simpler method is to generate the torus mathematically as a procedural volumetric material. This means that we can more easily vary how the density of the torus varies as it moves away from the center.
Firstly, we need to create a volumetric material that varies based on distance. This can be achieved with the following material :

This takes the 'object' coordinates and feeds this into both sockets of a Dot Product vector math node. The Dot Product returns a scalar value based on the magnitudes and relative directions of the input vectors. By using the same vector for both inputs the node returns a value based purely on the distance of the vector (actually distance squared) - this returns a value base on the distance from (0,0,0) - ie, the distance from the center of the mesh. This is passed through a Multiply node to allow the final result to be scaled, subtracted from 1 (clamped) so the result varies from 1 at the center to 0 at its edge, passed through a Power node to allow the falloff to be varied (to make it either more sharp or more fuzzy) and, finally, a Mulltiply node to allow it to be made overall more or less dense. This is then used as the Density of both a Scatter and an Absorption shader node - which are then combined for the final material output.
By creating a mesh (eg, a cube) to act as a 'domain' for the material and varying the Multiply and Power nodes, this can produce an effect similar to the following :

Small 'Power' (eg, 0.1) will produce a very sharp edge to the sphere while large values (eg, 10) will produce a more fuzzy edge. Reducing the first Multiply will increase the sphere's size while increasing it reduces its size.
To turn this into a Torus, we simply need to add some nodes to position the reference point (in the above case, this was the Origin) at various points along a circle - in particular, at the closest point along the circular path. The size of the circle will then dictate the size of the torus and the above Multiply and Power nodes will determine its fuzziness and thickness.
This can be achieved as shown below :

The center of the circle is at the Origin (0,0,0). The orientation of the circle is determined by a Normal vector - in the same way as for the Normal of a surface. Varying the Normal will change the orientation of the torus. The radius of the circle is controlled via an input Value (Radius).
The Cross Product vector math node is used to determine the direction of the closest point of the circle. The Cross Product always returns a vector which is perpendicular to both of the input vectors. By passing in the Normal to the first Cross Product, this will produce a vector that is along the plane of the circle - but at 90 degrees to the direction of the point being sampled. The second Cross Product takes that vector and produces one at -90 degrees to that - this will be along the plane of the circle and in the direction of the point being sampled (which will be the point on the circle that is closest to the point being sampled). This vector is Normalized (so it's magnitude is '1') and then multiplied by the desired Radius. The result of this can then be used to find the actual reference point on the circle that can be measured against the sample point to determine how close that point is to the circle.
We then have the Multiply and Power nodes used to control the falloff of the edge of the torus as in the previous example (but fed from Value nodes and given appropriate names).
This can then produce the following result :

Blend file attached.

You actually took the time to do the math! Cool!

Holy Brainmelt, Batman! I'm glad I asked first - there's no way in hell I could've worked all that out. hanks Rich, that'll probably work for me :)

An absorption volume shader is automatically darker around the thicker areas, maybe all you need is to use it instead of scatter, like here: Volumetric gradient based on density?
To be physically correct, you need both of them, mixed with an Add Shader. If you really want to control the scatter density, then continue reading...
If a (slightly random) cloud-like appearance is OK, then see this question: Is there an easy way to make volumetric clouds for Cycles? (you would start with a torus instead of a cube)
If you need precision, you can start with this one: Controlling volume density
Here (in the second example) the density is based on the X location. Now for a torus, the math becomes somewhat more complicated: the density depends on the  distance from the center, and on the Z location. I trust you that you can figure out the details :)
EDIT Just for fun, here are three torus-clouds (of type stratus, cirrus and cumulous) created with the cloud generator addon:

The cloud generator uses a particle system internally to set up the point density, so theoretically its source code could be modified so that the points are less randomly positioned.

@Ibalazcs: Thanks, but these suggestions address overall density variation, but not density with respect to proximity to geometry. A cloud sim is possibly the closest, but to configure and render the way I want it'll cost days for me to render. The paradox I have is I want an object to contain a 'mist', but I don't want the mist to get close to the geometry defining the mist container's shape. I want a far softer 'edge' to the mist (actually, NO edge), without having to blur it in the compositor.

Following the last suggestion you can control precisely the density with respect to proximity to geometry - you just have to set up the overall density variation so that it corresponds to the geometry. I didn't say it's easy...

Alternatively you can create a script that places vertices inside for a point density texture - similar to the cloud add-on, but then you have more control. Or add a particle emitter inside for particle-based point density, and set up the lifetime so that some particles die immediately, and all of them die before reaching the surface.

The last solution just replaces problems. You're asking me to swap out something I have trouble doing (advanced volumetric calculations) with something else I don't know how to do (scripting) :) Don't get me wrong - I appreciate your time - I'm just stuck. The manual says only the Position and Incoming outs of the Geometry node are workable for volumetrics. So I'm in a corner here.

So what about the particle system?

I discovered that the cloud generator also uses a particle system internally. Unfortunately it does not allow to change its parameters via the GUI, you had to modify the source code.


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How to repeat an emitter 'burst'
I have a plane acting as a simple emitter. It emits 10 particles from frame 1 to 4. And again from frame 11-14. And again from 21-24. Then there's a pause for 40 frames, and the entire sequence repeats, including the pause.
I need to find an automated way to cycle this emitter sequence. Ideally, the sequence could be repeated indefinitely using an F-Curve Cycles modifier.
The question below addresses a similar problem, but I'm looking for a way to use automation:
How to turn particle emission on/off?
Any ideas?

Yeah in the link you provided there was a good answer.
I made a clear answer out of it: Just animate the Velocity of the particles.

You can automate the curve with F-Curve Cycles modifier (Shift+E):

If it annoys you that the 0-velocity particles keep popping up, you can model a structure around the emitter:

Thanks Manu :) I asked my question two hours before you posted your answer in the linked question. If I'd known this question from May, 2013 was going to get a good answer two hours after I asked, I would've waited :)


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Fade a mesh out due to animated distance from Empty
In Cycles I have a cube with a red diffuse material on it, parented somewhere inside a larger Empty (type 'cube'). The Empty can be re-positioned anywhere, moving the cube with it as you'd expect.
I want to animate the red cube – JUST the red cube, not the Empty – to 0,0,-2 BU relative to the Empty (the Empty's local space). As the cube moves, the red cube should fade to invisible.
The key point is: I need to make cube fade out due to the cube's movement from the Empty, not a deliberate keyframe animation in the node editor or compositor. The cube's transparency value is dependent on the distance from the Empty's origin.
I'm guessing the node to use is Object Info in materials, and somehow configure it so that -2 BU in the Z-axis means the red diffuse shader transitions to a transparent fader via Fac input. But I don't know how to manipulate Object Info's output. Any help?

Do you have to necessarily use nodes? You may easily achieve it using drivers.

@PaulGonet: Thanks for the idea... Now I have to learn about drivers :)

Please check out my answer here: http://blender.stackexchange.com/questions/26064/how-to-bind-material-change-to-a-single-animation-action With the exact driver settings shown in my answer add a driver to Alpha slider in Blender Internal or to Fac slider of the Mix Shader (which mixes Diffuse BSDF with Transparent BSDF) value in Cycles. Happy blending man :).

The point is to be relative to the "empty" parent.
For that, use it as input in the texture coordinate node (left).
Then few calculations (simply the distance sqrt(xx+yy+z*z), modulated by the "2" input value), to drive the mix shader. If only the Z interests you, you can simplify that.

if the cube moves :

If the empty moves :

You can use only 1 Separate XYZ and use the outputs from it.

@Unix. Sure... you are right !!

Nailed it :) Manipulating Math nodes still fills me with fear. I really appreciate the help - Thanks!