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System is Slow when using booleans
Just started doing some of Blender Tutorials and was wondering why things are slowing down. Not things like pan and orbit, they're fine . But moving booleans around is painfully slow. Like when you try to reposition them to change the effect. This is not a complex model. I have a  newer Dell laptop Core i9-10980 2.4 GHz Nvidia Gforce RTX 2070 Super and 32 gb of ram. I thought this would be more than sufficient to handle the software. I was on the phone with Dell and they checked everything out and there was no difference running Blender afterward. Is there something in the preferences that I need to set?

Two options: learn not to rely on booleans and use modeling instead. Or change the solver on the boolean modifier from "exact" to "fast" (read: https://wiki.blender.org/wiki/Reference/Release_Notes/2.91/Modeling). The exact solver uses a lot more resources. Seriously consider going with the first option. Boolean operations are a lazy shortcut, that usually results in problematic topology.

Care to upload the file in question? Maybe it is more complex than it seems?

I'm not sure where to upload the file. As soon as I figure that out I'll post it. Also, I'll be reviewing the wiki. Thanks

@marchmoran upload here: https://pasteall.org/blend/

Using the Fast modifier instead of Exact (default).


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Jump/Scroll to selected object in the outliner?
How can I jump to the selected object in the out-liner, I've got over 200 objects in my scene, all named cube.___ ... and I can't seem to find my selected object. How can I jump to it?

If you have THAT MANY OBJECTS, consider renaming each cube a different letter and then moving the cube to a different layer. Shove them all back into Active again when done.

You can use Numpad . while hovering over the outliner, just like in the 3D view.

Tiny nit: doesn't have to be Numpad .  for me, regular . worked just as well.
Just to save time for anyone trying to hunt down the kb shortcut like me ;)

@pixelpax You are right, both the Numpad . and . is in the keymap.

Another less ideal way is to under the drop down at the top, to select active.

The down side is that it will hide everything else

I don't see that menu. Blender 2.93.

@DamnVegetables In 2.93, click filter icon and it is under Objects check box.

Another method I've been finding useful for dealing with the Outliner is to Duplicate the Area Window so it's actually another window.  Now it can be sized up and moved to another screen.  If you only use one screen, you can use Alt-tab to switch between the main Blender window and the Outliner window.  (For OS X, it's CMD+TAB)

Now you can split the window multiple times and scroll each one so that you can see(hopefully) everything at the same time with just a glance.

This is the keymap command you're looking for: outliner.show_active
Make a new keymap in the outliner section. I use the same key for Machin3Tools object focus - Z.

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Animated objects as hair particles
I rigged an object and animated it, and have set it as a hair particle (dupli object). It displays correctly, but animation is not being passed on... How do I make hair particle objects perform animation?
Note: I am aware that animation will be synchronized across all particles and am okay with that.

Hi there! I just checked it out and it works for me. I made a simple model, added a rig and animated it. Then I made a hair system an setted the hair particles as object: the model. And it works fine. What was your workflow?

You need to have your animated model and hair object on the same layer, or it won't update in the viewport (it will work only in render).

I could watch this all day long!

@Jerryno is there a way to randomise this animation

@ashwin use the group option under particle render and put multiple object copies with different animations inside that group;) Enable Pick Random to pick randomly from the group.

@ashwin also rotating the hair particles randomly will help (Advanced > Rotation).

Does is work for a Emitter particle sistem as well?

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Fracture part of the object
How would one fracture only part of the object with cell fracture add-on?
I have this object:

Can I only fracture center of the object, so that the top and the bottom are completely unfractured? I can't just make constraints since the object is glass in cycles and unwanted fractures are clearly seen... I tried using cursor close, I tried fracturing with child object, but regardless of what I do, I can't get only the center to fracture...

You could do this with a slight work-around.

In Edit mode select the top half of the object

Separate it from the bottom using , P -> Selection

In Object mode select the object you wish to fracture and run the cell fracture command

If you want to you can join them back together afterwards with Ctrl J

i wanted to perform fracturing only on the center of the object, but this workaround is a great way to go. thanks a lot!


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Unwrapping sphere in order to fit this image
I would like to make a sphere and unwrap it in order to apply a texture and a normal map so that it looks like this:

I've already created the 2d elements that will compose the ball:

But I really don't know how to morph them in order to create the final result.
Can someone please give me a hand?
Thank you!

I will not propose to unwrap a sphere to the texture, but how to make the sphere geometry as it appears in the reference image.

Start from a cube, subdivided twice.
Select opposite middle parts of each face and scale them down (around 0.2 for instance).
Do that for the three pairs of faces:

Then scale down the corners:

Add a subdivision surface modifier, then a cast modifier with sphere set to 1.

Refine the model: apply the modifiers then selecting the 3 edge loops starting from each 4 corners, bevel them:

The shape is done. Selecting the same edges you can now mark seams and unwrap.

Hey lemon, thank you very much for taking the time to record the full tutorial!
What I need to do from here is to export a lowpoly .dae file. Do you think I will be able to do it after modeling the ball that way? Thank you!

@AndreaSilvestri, yes, sure. This is a simple mesh, finally...

We can unwrap the sphere same as a cube, if the geometry of sphere is just subdivided and displaced cube:

Create a cube and give it these modifiers:

Proceed same as with unwrapping a cube. The texture can look like this:

Notice the bleeding over the unwrapped mesh. That is to not pollute the surface with green (or black in my example). You can also pack those faces much more efficiently if you like, to not waste any texture space:

Hey Jerryno, thank you very much for the advice! It's a great idea actually.
What I need to do from here is to export a lowpoly .dae file. Do you think I will be able to do it after applying your modifier?

@AndreaSilvestri, sure, when you apply the modifiers you can export the geometry. Just set the subdivision amount not too high..


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Cutting Out Volumes
I'm VERY new to Blender here. Now I've been trying to design a set of VERY simple 3D models, comprised of notched cubes occluded by a sphere.
A research assistant who is more familiar with Blender suggested I add an intruding rectangular prism and cut out its volume from the cube using the Difference Boolean modifier, but I just find this unnecessarily roundabout and it doesn't allow for the dimensions of the notch to be properly controlled.
My hope is to so somehow subdivide the cube into 16 smaller blocks, and be able to simply delete blocks out of the overall shape. I figure this would involve some sort of Extrude command, but I'm not sure how I'd do that.
The "local" and "global" models I've included in the attached image are hand drawings of the models I had in mind.
Thanks!

See this related question: http://blender.stackexchange.com/q/8639/599. However, I think the boolean modifier would give more control over the dimensions than subdividing..

Option 1  -
I believe the Boolean Modifier will be the simplest approach here, and give the greatest flexibility.
If you use the snap options (documentation here) it provides a very high level of control.  It would be possible to create tho cube to subtract, then use snap to center it precisely on the corner of the cube you wish to subtract from.  I've found this sort of approach quite useful in several situations.
Option 2 -
Looking at your models, only one side is effected, so it would be possible to model with extrusions as follows:

Select the face you desire to model the feature in. (Note, ctrl-tab in edit mode will allow you to change to face-select instead of vertices)
Move the face back by however far you want the feature to be inset. (press g then x, y, or z for the appropriate axis.  You can enter a numerical value as well)
Subdivide the face the desired number of times (w brings up a menu, subdivide is at the top.  repeat it twice for sixteen smaller blocks on the face)
Select the faces you want to stand out from the side of the block.
Press e to extrude them.

Let me know how it works.


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Blender 2.70 Fly Mode Camera: How Do I Change the Camera "Height" For Gravity?
In the new 2.70 fly mode, pressing TAB causes the camera to fall and hit any relatively flat surface (in Z axis).  However, when viewing scaled scenes at an arbitrary scaling, the camera falls really really far as though the "person" is incredibly tiny within the scene that you are walking through.
How do I change the camera/person's pov/player height so that I can fit in my scaled scene?

You can change the properties of fly navigation (including view height) in User preferences > Input > View Navigation:

Even if it's grayed out because the Gravity checkbox is disabled, changing the value will still affect the view hight when gravity is enabled by pressing Tab while in fly navigation mode.


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Can shapes with rounded corners be extruded with even thickness?
What I want to achieve is to extrude and scale the inner shape to the outer one like this:

The center of the shape seems to be attracted by the roundings, I tried to use bounding box center but this is still not what I want. Is there an easier solution then separated / extrude / join the parts?

[E], [Alt]+[S] isn't exactly what you are looking for but it's close.

@PGmath [Alt] while scaling for even thickness, never noticed this, thanks. .

[E],[Alt]+[S], [Shift]+(whatever the thickness axis is; x,y,z) would be what i would use.

@stacker Technically it's along vertex normals.

There is a way to use the inset tool like an extrude for a flat shape.

Select the loop of vertices you want to extrude inwards.
Fill in the area with a face F
Inset the selected area I
Delete the face

You do get small size variations in the new edge lengths around the curve compared to the straight sides but the amount is very small.

This only works gong inwards so you will want to scale your shape up to the larger size and then inset to the smaller size. With a bit of effort you can create a bounding box around your shape, fill it in with faces and press O while insetting to change to outset to enlarge your shape. Note in this example that the corners overlap and need cleaning.

There is a script that is specifically tailored to this task, it's called "offset edges":
http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Modeling/offset_edges
It has many options that are very helpful, for example vertices at the ends of the offset edge loops can be aligned with the adjacent visible edges etc. You can use negative values of "Width" to offset inwards.
Here is how to use it:

Shapes with rounded edges can be extruded, it is not impossible but by extruding one face at a time, then the extruded portion will create a mesh collision or an unnecessary space between extrusions. I suggest that you click all the desired face that you want to extrude and, extrude them in the direction that you want.


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How do I apply a simple armature that I made to a model?
I have a simple model that I want to animate for a short film. How do I attach an armature to a model? I want to be able to move the armature, which will control the model, and pose the model for animation.

In object mode right click the model than right click the armature with Shift after selecting both the model and the armature set the parent by Ctrl-p and choose the option with automatic weights.

object mode
Finally you can change the armature in pose mode and the model will deform.

object mode
To change the weights (how much a region of the model is influenced by the position of a particular bone) you can enter the weight paint mode and use the brushes to assign different weights.
For rigging a human character you should learn about Rigify which must be enabled in the user preferences / addons section.

weight paint  mode

Where can I find the "Weight paint mode". I only see Object/Edit/Pose modes while selecting armatures.

@adelriosantiago Select the model in object mode


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How can keyframes of properties be added to an action?
I tried to add keyframes for the emission value of a material to an action, but couldn't find out how.
Adding keyframes for a object's location works as expected but properties like emission only show up in the Timeline and Curve Editor.
A MaterialAction is created (only visible in the NLA Editor) toggling to edit mode Tab the keyframes are displayed in the time line. This MaterialAction is not accesible from the Action Editor.

EDIT:
Fweebs suggestion to use a driver works unfortunatly only in the 3D-Viewport but not in the BGE. I didn't ask specifically for the BGE because I was hoping for a common solution that works everywhere.

.blendfile here

You can't do it directly, but you can use a driver that ties the property value to the location of an object (typically an Empty or a bone in an armature) in your scene. That animation can be included in an action.

Without details of how to do this, this answer is largely useless.

Setting up drivers is a somewhat involved process and it's important to know what the ultimate goal is. Based on the question, this appears to be a rigging situation (which would be best suited using a bone in an armature), but we don't know for certain, so it was best to answer generally. In any case, more detail on drivers is available on the wiki (http://wiki.blender.org/index.php/Doc:2.6/Manual/Animation/Basics/Drivers)

You should include the link in your answer. It is more useful to other users that way. (And btw, forgive my "tone" I'm just trying to help :D)

As the tooltip mentioned:

Edit keyframes in active object's Object-level action.

So I bet that is why it is not currently supported yet?

However, you can still tweak it in the Dope Sheet mode, and use the Filter button to block other action types, if helps.

Thanks, I'm looking for a way to invoke the action in the BGE I'm currently experimenting with drivers but this makes things more complicated, once I saw a color changing action in the Action Editor it should be possible (perhaps the file was created with an older version).


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How can I remesh a curve that has been converted to mesh?
Is it possible to somehow remesh plane?
I have a logo that needs to be curved along an object. So I import the SVG logo and convert it to the mesh. But the plane has a bad distribution of polygons and vertices so when I use the shrink wrap modifier it breaks in some of the parts.
The remesh modifier looks to work only on models with some thickness. I ended up manualy cleaning the mesh, but wanted to find a faster way.
Beautify faces helped in one of four cases.

Maybe some images?

I added the image. The problem in this one is that the convert made the mesh kind of in horizontal way, so when I used shrink wrap there werent enough verticles to make the curve along the surface so the retopology had to be done.

Add Solidify modifier before Remesh. Then delete unnecessary faces after applying both modifiers. Also, is not it easier to put logo as a texture with alpha?

After it has the curvature I extrude it a little. It is not just like a texture. :-)  Yeah the way with the solidify and then the remesh isnt bad, but you have to select the middle and delete it, and sometimes it can be little tricky. So there probably isnt a direct way to change the order of popygon distribution in the plane. Other way I tried was to select just the outer edge and duplicate it, then apply grid fill which is kind of the output I want but without the process. Maybe they will add the posibility of remesh and decimate to planes later.

For this kind of work I would use the RobinBetts© method:

Import your svg, convert to mesh, simplify with X > Limited Dissolve.
Create a plane in front of your object, subdivide it vertically (probably more that what I've done in my screenshot). Delete the faces of this plane to keep only the edges.
Use the Knife Tool project to project these vertical edges on your object.
Give some corrections to your object so that it has a non-too messy topology.
Bend it (with Simple Deform / Bend mode or other) it has what it needs in terms of vertical edges to bend nicely.

This looks interesting, will definitely try.

Curves converted to mesh have terrible topology.
Delete the faces on the mesh but keep the outer edges.
Then recreate the faces with Grid Fill
See:
How to fill a 3D bezier curve?
How do I fill an area with faces lined up in a grid?

Yes, you can! Carlo suggested a very quick and convenient method using Detail Flood Fill in the sculpt mode:
https://blender.stackexchange.com/a/60852/34311

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


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Is it possible to render a 3D model and image from a 2D picture
I have begun to create custom car and motorcycle works so that I build them in real life.
Is there anyone that has had any luck entering 3D models from an uploaded 2D image, and if so, how was it done?

https://blender.stackexchange.com/questions/63246/how-do-i-make-a-3-dimensional-character-out-of-flat-picture

for the moment there's not magic way to convert 3D to 2D as explained in the link given by Susu, but maybe be more specific, what kind of object, etc... you can quickly model something that looks like your object and project a texture on it for example

You never know.. a couple of papers down the line.. AI might be able to make a good guess :D

I’m trying to take 2D pictures of my motorcycle and then somehow form them into a workable 3D model that I can then toy and play around with in order to see how it is now and compare side by side a newer customized model


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Audio was out of sync whenever I didn't play it from the start
Whenever I don't play the animation from the start, the audio would be out of sync (I'm animating a part of a music video), and when its out of sync it'll probably be hell to try to do lip-syncing. I've tried stuff like making the audios length the same of the actual project (which didn't work).

It's hard to guess what the cause may be in your particular case, so preparing some example .blend file reproducing your problem could help others to figure out what's going on. I only ever got a desync when my scene was lagging, indicated by red FPS number during playback, but it could as well be a codec problem.

First make sure that the audio is in WAV format, not in mp3. Then, in the timeline Playback options set the Audio Sync either to frame dropping or AV-sync.

Follow-up question: https://blender.stackexchange.com/questions/209987/2-audio-was-out-of-sync-whenever-i-didnt-play-it-from-the-start


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When I render something, there's an indent in the model, but when It's not rendered there is no indent. how do I fix this?

I just can't find what's wrong

Here's the file of it, if that can help with it

Neither can we from two screenshots. You will have to addd more information to your question.

@DuarteFarrajotaRamos what type of information would you need? because I don't know what I would need to look for, to give information. Sorry

Everything, object topology, modifiers, materials, textures, screenshots.

please share your file: https://blend-exchange.giantcowfilms.com/

There are some problems with your topology. Also, if you want to stay low-poly without any Subdivision Surface, you have to use the Auto Smooth, otherwise the twisted planes of your object will always create artifacts.
First of all, you have unwanted faces. If you go in Edit / Face Select mode, you can see some faces squeezed between faces. It has nothing to do with the problem you're talking about but anyway you need to correct that because it's not good to keep this kind of topology. It must have been created by some accidental extrusions. So select all your vertices with A and click W > Remove Double, it will merge all overlayed vertices and remove all these unwanted faces. It's not the only problem of your topology but it's the most obvious.

Now, about your problem: Your object is made of several planes that are not flat but twisted like chips, so, as you didn't smooth your object with Smooth Shading and Subdivision Surface modifier, which would have helped to smooth these surfaces, they do appear like triangles and not like planes.
If you want to avoid these artifacts you have several solutions, you can either:

Use the Smooth Shading (in the 3D view Tool panel displayed with T > Tools tab > Edit > Shading). But it will give non very aesthetic gradients as your object doesn't have enough polygons.
Keep this Smooth Shading but add a Subdivision Surface modifier so that your object has virtually more polygons.

But these solutions are interesting only if you want to give your object a smooth and high-poly appearance. If you want to keep it low-poly you should use this trick:

Keep your object Flat and with no Subdivision Surface modifier.
Go to the Properties panel > Data > Normals and enable Auto Smooth. The Auto Smooth option is supposed to determine the angle below which the Smooth Shading will happen, but in Flat Shading it will also make your twisted plane look flat and uniform.

If you do not want to go into the depths of moonbots lesson, you can fix your model with 2 clicks in this case.


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Converting a mesh to voxels
Is it possible to convert a mesh into a voxel image?
This operation would make white voxels inside the mesh, and black voxels outside the mesh, and would either:

write a standard 3D image file format, or just a raw voxel dump; or
create a stack of 2D images in each axis

a script would be the better solution but you can use dynamic paint :  animate a  plane ( the canvas with high dry speed)  to go through the mesh ( the brush ) then bake the image sequence

I'm fluent in Python but have never made the dive into learning bpy. This is just a once off operation for me, so I'd rather not spend the time scripting. I'll see if I can figure out your dynamic paint suggestion.

I didn't try, but there is this thread  (though OP there asked about .obj, but still maybe some general usage)

@Chebhou the dynamic paint solution worked well. Want me to add it as an answer?

@ajwood of course, go ahead

As Chebhou suggested in the comments, the 2D image stack can be achieved with dynamic painting an animated plane.

Add a plane, and animate it to pass through the main mesh
In the physics panel of the main mesh, enable Dynamic Paint and make it a brush
In the physics panel of the plane, enable Dynamic Paint and make it a canvas with these settings:

Format: Image Sequence
Dry time: 1
Dissolve time: 1

In the Dynamic Paint Output panel, click "Bake Image Sequence" to write out the plane/mesh intersection at each frame of the animation.


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Viewport material view
I'm wondering why viewport material shading would draw an image texture fine, but doesn't seem to be able to draw a procedural texture:

The same is true for texture shading. Is it possible to get procedural textures drawn in the viewport without having to render?

No.
This is because the procedural texture is actually calculated by the render engine. The closest you can get is by "caching" the texture to a conventional raster image via texture baking, then using that as you would any other image texture.


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Posing Hair in Animation
I was thinking about making a hairball character. The character is simply a sphere with a hair particle system. In addition to it's base hair, it'd have a couple longer tighter hairs to act as arms.
I'd want the "arms" to act as regular hair (i.e. hair dynamics) but have the ability to be posed when it's time to reach out and grab something in its environment.
Does Blender have the tools needed for such an organic rig?

You can use curves as hair guides. Set their maximum influence to create a small "sphere" around their base which influences the hair system, which will allow short hairs, and under the curve's influence only, long hairs.
Than you can use shape keys to animate the curve. I'm not sure if you can use an armature but that may also be an option through some other round about method.
Here is a step by step, sorry there is no screen shots.

select an object and create a particle system. Select "Hair" as
the type. You will see some strands.
create a bezier curve (shift+a -> curve -> bezier curve)
this is the step that may have been unclear sorry. Select the
curve, and go to the Physics tab, and click "Force Field". In the
properties below, under "Type" change from "Force" to "Curve Guide".
There will be 2 circles, a dotted and solid at each point. The solid
sphere is the root of the guide.
Check the "Use Max" checkbox. This will change the root to a dashed
sphere. Set the maximum distance as desired. It will change the size
of that sphere, and any hairs inside of it, will be influenced by
the hair guide.

Now changing the hair system in particle settings will affect the normal parts, and the hair guide fill affect some specific parts.

I think this should be able to do the trick. Thanks!

Pretty sure a hack to get bones working is to copy/convert the curve to a mesh, and make the mesh vertices parents to the edge handles. Then bones move mesh, which move the curve, which move the hair, which pleases me greatly.

There is another solution. You can use the "hook" modifier to hook the curve control point to a bone, or any object. But your solution does sound interesting!

Your answer was good in theory, but now that I'm trying it, I'm having trouble figuring out how to make a "hair guide." Could you please add that to your answer?

Sure no problem. Answer updated. :)


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Vertex Paint on faceless model
Is it possible to apply vertex colors to vertices that aren't part of a face?
I've tried using vertex paint mode in the Blender application, and also directly modifying a vertex paint object via python, neither or which worked.

The wiki
says:

The color of all visible planes and edges attached to the vertex are
  then modified with a gradient to the color of the other connected
  vertices. (Note that the color of non-visible faces are not modified).

As I understand this, it works on gradients which are not available without edges and faces. Thus you can't paint isolated vertices.

I don't care about visualization though; I just want to attach values to vertices

@ajwood I already wondered what you're actually trying to achieve, you also can't add custom-properties to vertices , check the last post by codemanx here: http://blenderartists.org/forum/archive/index.php/t-313260.html I wouldn't have expected such. An alternative that always works in scripts is a mapping: vertex-id to custom-data.

I'm doing some scientific visualization.. I've got a few thousand edges/curves, each with a value which will determine their colour. I can either add them as separate objects (color based on a whole-object property) or as one big object (color based on _______)

I'm trying to figure out which answer to accept for http://blender.stackexchange.com/questions/12143/rendering-unconnected-edges


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Particle System Dupli Object's Children Not Rendered
I have a model which consists of a few levels of parent/child relations, with a single common ancestor P at the top. I'd like to set up a particle system which emits instances of the whole model, but when I set the dupli object to P, it emits only P.
It's going to get ugly if I have to join all of the objects into a single mesh.. Is it possible for a particle system to emit a parent with all of its children?

I'm afraid this is going to be a duplicate question.. I've found it tough to search for, as since regular particle children are hogging the google hits..

Group all the objects and under the particles render tab set the render to Group and check whole_group.

In Blender 2.81, this is now done with Collections instead of Groups. Be sure to select the checkbox "Whole Collection".
In this example "doughnut" is the parent object, which has a number of child objects:

How about I have 2 objects with children, and spawn those two objects randomly? It's not working with collections. For collections it's just listing all objects inside it (even though they are parented to empty). It's driving me nuts.

I'm so confused. When checking the whole collection for a particle system, the particles are no longer emitted from the actual emitter, but from some sort of offset between the emitter and the object. Any idea why?


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Rendering freestyle lines in Cycles
I've been using BI to render objects as meshes using freestyle edges. I'm now trying to learn to use Cycles. Is it possible to render freestyle edges in Cycles? If so, how?

Related: http://blender.stackexchange.com/q/562/599

No, freestyle is not yet supported in Cycles (and I'm not sure it ever will be directly supported). You could work around the issue by using render layers and grabbing only the freestyle pass from BI:

Then mixing it with the Cycles pass in the compositor.

How is this supposed to work?  Blender doesn't allow you to change the rendering engine for render layers.

@ZauberParacelsus, true, but it does allow you to change renderers for different scenes. You have to duplicate the scene (after your sure your not going to change it) and set the engine to BI.

Update
This is now in master, and will be in 2.72.

This is possible using this experimental patch, which may be included in master eventually.
Currently if you want to test it, you'll have to build blender yourself, or try and find a prebuilt version on a site like graphicall.


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Object rotation in node
I have a field of ellipsoids with various rotations. I'd like to colour them by their rotation. Is it possible to get an object's rotation in a cycles material node?

AFAIK, For controlling via location, you can use Object Info node. But via rotation... It would be a nice feature too. A new vector type for object Info node. :) I bet currently you have to script for batch control.

I wonder if adding it would be trivial.. I might have to see if I can get myself on the development team :)

Sort of..
You can insert a "Value" node (under Input) into your Cycles shader, then add a driver to it (right-click the parameter and select Add Driver); get the driver to copy the rotation axis of whatever object you want to use:

With the Value node selected, go to the Graph Editor.
Switch mode from F-Curves to Drivers.
On the left hand side of the editor, find the "Value" inside Material > Shader Nodetree and click on it.

At this point you might need to reveal the panel at the right hand side of the editor - hit N if you can't see it.

In the "Drivers" panel, change "Type" to "Averaged value".
In the variable panel, make sure "Transform channel" is selected, then specify your Object from the input by name, change Type to "X Rotation" (or Y rotation, etc) and you should see its current value appear.

You can then attach the output of your Value node in Cycles to a Hue/Saturation node, or to the Fac of a Mix node to alter the colour. If you want each rotation axis to be available in the material, add a separate value for each rotation axis.
If you want to do something like map each axis directly to a part of the colour - e.g. X becomes R, Y becomes G, Z becomes B - add an RGB input node instead, right click the colour and add a driver to that. You can then find it under "Drivers" the way you might have found the value, and you can drive the four different components of the colour (R G B and A) individually.
Worth noting: the rotation value will hit the driver as radians, not degrees. It's also possible that the driver will get an input which is less than zero - you can get around this to an extent by setting the Type to Scripted Expression and using an expression like "abs(var) % pi" to keep the colour away from black.
There's an annoying drawback to this method though: as far as I know, you'll need to set the driver and material up separately for each object - so you'll end up having as many copies of the material as you have colour-changing ellipses. If your Cycles node setup is particularly complicated and you still want to be able to tweak it, you might try Grouping all the nodes in your material except for the Value, but use the Value as an input to your group. If the Object Node had X/Y/Z Location/Rotation/Scale, this wouldn't be necessary.

I can't get this to work.  I've tried using rotations between -1000 to several thousand degrees to see if range was a problem and there is no difference in the output.  Oddly enough, if I change the slider for the Value node, the rendered output changes even though I get a message saying  "Cannot edit a driven value, see graph editor for the driver setup."

Well it works.. the annoying drawback to pointed out is going to make this impossible though (I'm applying the material to a couple hundred or so objects), so I'll have to script it.

Thank you to quollism who mentioned drivers can do this, i've attached some visuals to help guide the process.
To get data into a node that isn't normally supported by existing "Input" nodes,
we can use Blender Drivers

I find it useful to having a animation playing working with drivers. animation playback is recommended

Rotation in blender is often represented as an XYZ Euler, first x, then y, then z, so we need to copy three values to copy a rotation
I recommended adding one "combine XYZ" converter, since this will directly operate as a vector in nodes, but three individual "input values" works too
select the rotation source, I believe this value, when sampled by the driver will be "fully updated", including all parent transforms in its transform. Copy this, Object -> Rotation, X  right click "Copy as New Driver"
select the rotation destination (our Combine XYZ's X input),  right click "Paste Driver"

repeat for all X Y Z components,
this works in compositing and geometry nodes too I believe.

Source X
Copy as New Driver
Dest X
Paste Driver

(repeat 3x)

Shown below is a visual of the process,
(its too big to be a gif so it won't embed directly)
https://i.imgur.com/X9g1D02.mp4


text:
Shadow from camera vs shadow from reflection
Is it possible to distinguish between shadows viewed directly from the camera, and shadows seen in the reflection of an object?
For example, the shadows circled here:

From the cameras's perspective, I'd like the tile to disappear (along with its shadow, diffuse effects, etc).
If I make the tile transparent for camera rays, shadow rays, and diffuse ray, I get this:

I'd like the shadow to be visible in reflections though. If I remove shadow rays from my transparency condition, I get this:

So here's what I'm trying to achieve:

Is there a way to determine whether the shadow is viewed directly from camera, or if it's being viewed through a reflection?

I'm pretty sure the only way I can do this is with by duplicating my scene, tweaking the materials for the two transparency conditions, render twice, and combine in the compositor.. I find this sort of thing very difficult to maintain, so I'd love if someone can come up with a different solution!

So for this I would use render layers. This means you can't really view the effect 'live' in the viewport, but it will be applied when rendered and composited.
I have 2 render layers:

Render layer 1, called 'Main', renders layer 1 which holds the sphere and light only.

Render layer 2, called 'Floor', renders layer 2 which is the floor object and excludes layer 3, which is the red plane.

'Transparent' must be enabled in film section of the Render tab to allow layers to be composited together.

Note: All 3 scene layers should be made visible before rendering. All 3 layers are required, the render layers take care of what appears in the render.
'Main' render layer will only include the sphere, but will still be effected by the other layers, so will include the plane and floor in the reflection.
'Floor' render layer will only include the floor object and will only be effected by layer 1 because red object is excluded on layer 3.
These render layers can then be combined in the compositor:

Which results in:


text:
I don't know how to reset the workspace
I messed up my workspace, here is how i want my workspace to look when i select uv mapping for example:

but this is how it looks like on my screen:

You could do a factory reset: File > Defaults > Load Factory Settings.

Read: https://blender.stackexchange.com/questions/129387/how-to-close-windows-in-2-8?


text:
Trouble aligning the object in render view
I was moving objects in Edit mode when I should have been moving them in object mode but now I cannot seem to correct the positions.

I've tried setting the origin, but it hasn't worked for me.

How do I do this?

I should say that applying transformations also doesn't seem to help.

There should be Align option to align objects. You may also use SnapTo to align.

It doesn't seem to work. Aligning objects doesn't change anything, though I might be doing it wrong.

Change the displacement method to bump instead of true displacement


text:
Grey objects in the material preview and the rendered mode look in Eevee render
In object mode, the objects look normal:

However, when in eevee, the material preview and the rendered mode look like this:

When I zoom or rotate I get this weird outline:

Please note that this is a brand new blender project in the images, but this same issue applies to all my projects. I have already tried setting back my driver but that hasn't worked. I've also tried downloading earlier versions of Blender, but somehow I get the same issue.
PC Specs (if that helps):
Operating System: Windows 10 Pro 64-bit (10.0, Build 19041) (19041.vb_release.191206-1406)
Processor: Intel(R) Core(TM) i5-8500T CPU @ 2.10GHz (6 CPUs), ~2.1GHz
RAM: 8GB
DirectX Version: DirectX 12
Card name: Radeon RX 580 Series
Any help would be much appreciated.


text:
I can't find the ` apply ` button in subsurf modifier
After I made desired shape with subdivision modifier, how do I turn it into a mesh, there is no apply button in modifier.

You have to click the little down arrow in the modifier options. The apply option is hidden underneath:

It works, THANK YOU !!!


text:
Render doesent show almost anything (material or textures)
a little while ago was everything working perfectly. But now, when i have even just basic cube in the scene, then when i want to add texture or materieal, or even if i wont add any of them to the cube, when i go to Rendered viewport shading, all i see is this (just a grey cube with nothing on it, i have set the color tu blue but nothing):

And when i render it it shows just checkered cube like this:

I know its probably gonna be something dumb, but i just cant figure out what the problem is. Thanks for help.

Does this answer your question? AMD GPU Material in "material preview mode" and "rendered mode", is entirely gray as background. Only outline is displayed   Similar  https://blender.stackexchange.com/questions/linked/204297?sort=newest

Thats it, that helped, thank you


text:
Subtitles or how can a text object be edited before a frame is rendered?
A text object's text is supposed to show information like a subtitle. How could the text be changed on a frame # based trigger?

An application handler could be used to read subtitle data and display it by editing the text object.
import bpy
from bpy.app.handlers import persistent

@persistent
def frame_change(arg):
    print("Load Handler:", bpy.data.filepath)
    t = bpy.data.objects["Text"]
    label = ("Frame # %d" % bpy.context.scene.frame_current)
    t.data.body = label

bpy.app.handlers.frame_change_pre.append(frame_change)

There's no need for the @persistent decorator, unless you want the app handler callback to survive .blend file loading (also new file). API Docs


text:
What causes a face to be created only partially?
Trying to create a face Make Edge/Face F doesn't create the face completely.

Why remains this triangle unfilled?
.blend file

There are a lot of double vertices around the face, which meant that the selected edges around the missing triangle were not actually connected to the rest of the selection.
To fix this, select the vertices around that area, or select all (A) and press WR to remove doubles.
You seem to have a lot of doubles, it removed 305 vertices for me. Perhaps an accidentally applied edge split modifier or edge split operator (CtrlE>Edge Split or D)? It's possible to split edges without.
Identifying doubles:
You can tell that the upper left edge is not connected to the selected vertex because the orange gradient that normally appears along selected edges is not visible.

After merging the double vertices with Remove doubles it looks like this:

Now fill will work as expected:

This is really good I think because this person seems to be just starting out, it's what's needed for this person at his or her skill level.

Common Cause of Mesh Editing Problems
I have found one of the most difficult to detect causes of odd mesh behavior is when vertices, edges or faces exist in the same spot (overlap/are duplicates). This can cause your mesh to be non-manifold and can also cause odd problems like the one you've encountered.
Automatically merge vertices moved to the same location
One easy way to avoid creating duplicate vertices is this: while in Edit mode, enable "Automatically merge vertices moved to the same location":

If you have this enabled when modeling, you most likely won't have to use Remove Doubles later on. NOTE: Enabling this will only merge vertices from that time on while modeling -- it will NOT merge already existing overlapping vertices. To merge already existing ones, use Remove Doubles by doing either of these while in Edit mode:

Tools panel -> Tools tab -> Remove section -> Remove Doubles
W -> Remove Doubles

Overlapping Edges
However, enabling Automatically Merge Vertices and Remove Doubles won't help you in the case of overlapping edges that have different start and end vertices. I've found 2 common causes of these kinds of overlapping edges: Extruding and Make Edge/Face.
Extruding
Here is a video showing how extruding during editing can cause overlapping edges:

Here, the two edges get overlapped by the one long extruded edge. Notice how even though Automatically Merge Vertices is enabled, the middle vertex (the one moved around at the end of the video) does not get merged because when the edge is extruded, it doesn't have a vertex right there to merge with. The same situation can occur when extruding vertices or faces.
To avoid this problem, don't extrude past/over a vertex (as show above) -- extrude TO each vertex, as shown here:

Since Automatically Merge Vertices is enabled and all edges have they same start and end vertices, they get automatically merged and you don't have problematic overlapping edges or duplicate vertices.
Make Edge/Face
If you use F to make and edge or a face that overlaps a vertex, you'll get overlapping edges, as shown here:

How To Find Existing Overlapping Edges
One easy way to find overlapping edges is this: while in Edit mode use CTRLSHIFTALTM to select & highlight all non-manifold geometry. Now examine those areas and if you see a place where it looks like it should be manifold, but it's highlighted, check there for overlapping edges, duplicate vertices, etc.
One way to find them is to select a vertex and see if it's highlighting indicates it is properly connected to all the appropriate edges. Here's an example of a selected vertex who's highlighting indicates it's not properly connected:

See how it's highlighting doesn't include the horizontal edges? That means it's not connected to them.
Here is a vertex that is properly connected:

It's highlighting includes all four of the surrounding edges, so you know it's properly connected to them.
How To Fix Existing Overlapping Edges
Once you find the offending vertex, grab & drag it to see if a hidden overlapping edge is revealed, as shown in the videos above. Once found, delete the overlapping edge, then put the dragged vertex back into place.
One trick I discovered about how to put the vertex back into place easily is when you are first dragging it out of place, only drag it on one axis, rather than freely in 3, because then you only have to snap it back into place on one axis, rather than 3.

Great answer. I like the general approach to this. X > Limited Dissolve is another good function for cleaning up floating or excess geometry.

Thanks, it was a huge leap forward for me when I discovered all these things that were making my meshes non-manifold, etc.

What I really wish is Blender would have a "Automatically merge all geometries moved to the same location" or some such feature like Remove Doubles called "Merge Geometries" that would merge overlapping edges & create the necessary vertices, remove doubles, etc. That would be SO great & would speed up the whole modeling process/model clean-up process.

This is because the mesh isn't continuous at a particular spot, (maybe you did an accidental rip V) or there is excess geometry floating somewhere. Run a W > Remove doubles operation and it should work after.
Other things you could try are to look at your mesh in wireframe view to see if you can spot any odd bits, make sure there aren't any inside faces etc and or box select the problem region and perform a X > Limited Dissolve operation.


text:
Why can only one inner region of a plane be subdivided?
Starting from this situation:

Subdividing W the inner rectangle leads to the following model, please notice that the center points of the adjacent rectangles have been displaced. Subdividing other rectangles is no longer possible.
To analyze the behaviour, I tried to subdivide the outer regions first this works flawless.
Why is that?

View from vertex mode:

.blend

The outer faces are now ngons. When you try and subdivide the outer faces they are being subdivided, which you can see when going into vertex mode:

The subdivision can't happen like before because while the faces appear to be rectangles, the topology is no longer quad based.

Thanks, I don't have the superfluous vertices in the middle of an edge. Only the ones needed for the ngons.

No, they're the result of subdividing the outer faces after subdividing the internal ones first. You were saying that it was not possible to subdivide the outer faces and I'm saying they were being subdivided even if it didn't look like it.


text:
How can unwanted rotation of hair particles be avoided?
A hair particle system is used to emit leaves from an animated tree, for some reason the leaves rotate. How can this be stopped? I know that I could convert the particles to meshes, but I would prefer  too keep the particles.
Two subsequent frames:

The settings:

Emit from faces instead of vertices makes it appear a bit more stable (but then no more particles will be emitted at the tips of the branches), not all leaves are rotating.
.blend

You have Newtonian Physics enabled for one thing. And velocity is set to 1. Does that change anything?

@NoviceInDisguise Setting physics to No or Velocity/Normal to 0.0 hides all leaves.

Interesting! I haven't run across this issue before, so I might need a .blend to experiment with.

@NoviceInDisguise Thanks, I added the .blend it took a while to get rid of 50mb textures..

It only acts that way when the particle system comes after the armature in the modifier stack. So the armature deform modifier is somehow messing up the particles . . . I'll let you know if I find anything else.

@NoviceInDisguise Thanks, could you add this as an answer.

This sudden odd orientation change appears to be caused by the Armature modifier on the tree. The particles seem to respond much differently when the vertex positions are moving (it could possibly be because it is changing the size of the faces).
One way to combat this would be to move the perticle systems up the modifier stack until they are before the Armature modifier.
So instead of this:

You would instead end up with this:

It is important to note that when the armature moves the mesh, the particles might not move with it. You will need to convert to a mesh and add it to the armature deformation.

Unfortunately the leaves are no longer animated when the modifier order is changed. I noticed this after several hours of rendering.

I'm sorry about that! I put it in the answer at the bottom when I first posted.

Oh sorry my bad, didn't read to the end I was already happy after your comment.

I found a way to keep the unconverted particle system by enabling Rotation and changing the Initial Orientation (the conversion to mesh brought some performance issues).
(Editor's Note: For stable rotation under mesh deformation, make sure to UV Unwrap the mesh first to supply Tangent data to the Particle System. This stabilizes rotation by having  the y-axis of our particle follow the "normal" and the x-axis follow the "tangent" when Normal-Tangent is selected further below).
Step 1: (UV Unwrap)

Step 2: (Check Regrow and Advanced for the particles)

Step 3: (Check Rotation and change to Normal-Tangent)

Also, make sure that the faces on the mesh are only triangles and quadrilaterals. Hair tends to be unstable when faces have more than four edges.

Very interesting!

For me, checking the "Regrow" option solved the issue. The "regrow" regrows the hair every frame, so the armature doesn't affect the orientation of the particle system.


text:
How should an animated character be moved while repeating a walk cycle?
I created a walk cycle as an action, placed it in the NLA editor and repeated the cycle.
For each repetition the character jumps back to the starting position, what are some options to move the character forward? (The ending position should be starting position of the following repetition of the action).
Starting position:

Walking until last frame of action the same action should follow but the position jumps back to the origin. (Same as image 1 except current frame has advanced)

I also tried in the NLA editor (same effect as above):

For each cycle, make sure the support foot (one that's planted to the ground) moves back in linear speed. Use Set Keyframe Interpolation T > Linear for the support foot's first keyframe. You should also know the distance it moves back. Just Ctrl-drag (snap to increment) so the distance value is easy to reproduce, no need for guesswork.
Next, move the root bone, at the same distance, also in linear speed. Here's an example before moving the root bone, using David Rodriguez's Carmen rig (box moved linearly, standing in as the ground):

and after moving it [GIF] (box still as ground), and the animation's graph:

Support foot's position within the cycle represents how far the ground "moves". By moving it at linear speed, with known distance, it's easy to move the root bone in a way that will counter the support foot's.
NLA-based Walkcycle
The workflow is also applicable for non-linear animation, with slight difference. Create a separate action data for root bone's animation, put it above the walkcycle track:

Though the walkcycle's action is the same, the root bone's need to be extrapolated linearly. For the root bone's action, execute Channel > Extrapolation Mode Shift-E, and select Linear Extrapolation. That way, the root bone's animation strip only needs to be scaled to match the walkcycle's, no matter how long is repeated.

Thanks for the quick response. Why should the support foot (in mhx rig called master-floor) moved back and not forward?

I don't know mhx rig, but master-floor sounds like the root bone, to me. The support foot is the foot that plants to the ground and supports body weight, in one half of a walkcycle.

think that when you animate a character moving you have to think that is as if you are seeing it with a camera attached to its root, so you see (and animate) the apparent movement of the foot going back but it will be still to the ground when you move the root forward.


text:
Can the orientation of objects emitted from a particle system be controlled?
When emitting objects from a particle system (boids) the objects appear with random orientation, while they move it would look much nicer if e.g. a spacecrafts nose would point into flight direction.
It seems to have a leader at the first position of the Boids Brain panel helps but then the particle tend to clump, when separation is added they start to move with random orientation.

The mesh should be rotated in Edit Mode so that the nose points into the emitting direction, then the will always point to the flight direction.

The rules to prevent clumping:

And the mesh should be such that "forward" is the positive (local, if the object containing the mesh is rotated) Y axis.


text:
What are the options to extrude fingers from a low poly hand?
The technique I currently use to create faces to extrude fingers from a base mesh is: Cut the front and upper faces with the knife tool (as shown in the image).
Using the knife tool creates n-gons which influences the topology, creating more loopcuts would be continue over the arms to the whole body where they are not really needed (and would create more work to adjust them).

Are there any alternative techniques?

What exactly do you mean? Topology for hand models in general or just low poly hands? Also, how low do you mean by low poly?

@CharlesL Added more info to the question, is this now more clear what I'm asking?

You can use inset, but I have only tried this for three fingered hands:

Individual inset (II) with both faces selected:

Select the faces inside the new inset, move them forward a bit, inset again:

Select the faces inside that inset and move them forward, extrude middle section:

Extrude fingers:

Using gandalf3 answer and combining it with a diamond shape which splits one loop-cut to three I found this all-quads solution:


text:
How can unused tracks be removed from the NLA?
With autokeying enabled I accidentally moved a few objects, unfortunately they now appear in the NLA editor. I removed the actions saved and reload but I can't get rid of the entries.

This behavior has been changed after 2.66a. Just tried to discuss with the designer. As explained, it is one of the main ways to prepare some places to add NLA strips from pre-made actions, and got its advantages, too.
To make them invisible, click the third toggle on the header to exclude them from displaying.

This solves the problems with objects. To remove the ones with Compositing Nodetree, I had to delete (in Python console) the Nodetree Actions. I don't know if there is another way to do it.

@MarioMey Can you provide an example? Just wonder why the compositing tree data relates to the problem here.

When we create a node group and animate something inside it, a new Action is created and appear in NLA as an Action (not yet track). When we ungroup the group... or clear keyframes, most of times, it disappears, sometimes, it doesn't. And here is where we would need to delete the empty Action. You can do it with Blender console, like this: bpy.data.actions['CompositingNodetreeAction.001'].clear_user(). Maybe you want to delete it, but I prefer to reopen the file. See this [screenshot] (http://pasteall.org/pic/index.php?id=108866) before deleting the Actions.

Be careful when using D.actions['CompNodetreeAction'].user_clear() and removing the Action like D.actions.remove(D.actions['CompNodetreeAction']... you can make Blender crash (it just happened to me). It's better only to clear users and see what happens. Maybe you are using that Action somewhere else.

authors: Сергей Лебедев


text:
Why does a multiplied texture with alpha loose detail information?
The left image shows the texture mapped to a plane, the right one is original image in the UV Editor. The rendered image looks extremely blurred. What would be the correct material and texture settings to have only the alpha part (check pattern right) invisible?
.blend file

Material and texture settings are:

Is the left image the rendered output, or in the textured 3D view?

.blend will help with trouble shooting. I have a feeling that it might be caused by mit mapping. also, how is it unwrapped?

@David it is the rendered 3D-View.

@user2926289 I added the .blend, it is a simply a plane unwrapped.

Setting the Blend Mode to multiply isn't necessary.
Material Settings:

Specular

Intensity: 0.0

removes this:
Transparency: On

Method: Z Transparency
Alpha Slider 0.0

Texture Settings:

Type: Image or Movie
Image: The Texture Image
Use Alpha: On (Otherwise darker parts of the image which are supposed to be opaque will be partially transparent)
Image Sampling

Alpha: Use : On (Otherwise darker parts of the image which are supposed to be opaque will be partially transparent)

Mapping

Coordinates: UV
Map: UVMap

Influence

Color: On (1.0)
Alpha: On (1.0)

Blend: Mix (Default)

Settings to compare:

Result (left rendered, right image editor)
Image source by Luc Viatour / www.Lucnix.be

Result zoomed


text:
Can snapped vertices be automatically merged?
Two vertices snap together when snapping during transform is enabled with snap onto self :

How could both vertices be merged?

not sure what the question is asking, you want auto-merge to merge both?

In case anyone else is confused, you might want to also see this chat conversation

I rephrased this, now it should make more sense.

AutoMerge Editing might be what you are looking for.  It can be toggled on and off by clicking the entry.

EDIT: I've added the image posted as a comment by username: gandalf3 since he pointed out that there is also toggle button in the header bar which makes this feature easier to access.

Also note that there is a toggle for this in the header of the 3D view. screenshot

It's on the top-right of the 3D View-port in Blender 2.80.

Update for blender 2.8 OSX (in addition to Meetai.com's comment)
AutoMerge Editing can be found

far right above the outliner within dropdown button Mesh Options
properties panel first tab, Mesh Options. (first tab active tool and workspace settings)

Source: https://blenderartists.org/t/where-is-automatic-vertex-merge-in-2-8/1119468/3


text:
How could penetration between human models be avoided?
In a fight scene I have several actions where the movement is only limted by the freedom of movement of the rigged bones. When a punch hits the body of the other character it shouldn't penetrate the body hit it should rather push it away or stop when the collision is detected.

Can this be achieved with rigid body constraints?
The two characters are linked into the scene and have proxies,
I tried several settings in this dialog but whatever I do it seems to have no effect.

No, Blender isn't capable of doing that (yet). I've tried combining armature-based animation with physics-based cloth/rigid body simulation, and the latter always override any manual animation I've made.
I'd try to limit the range of punch based on bounding-box proximity between the two characters, or trigger a knocked-back animation (faster than the punch animation) depending on how far the punch animation is played + bounding-box proximity.

Thanks, could you please add a reference on how bounding-box proximity is setup? Or is there another name for it I couldn't find any resources on that topic.

That'd require some Python BGE coding, which I have next to no experience in. I've used bound_box for similar purpose, but strictly for F-curve based animation. Sorry.


text:
Modelling a spiral around a sphere
I'm trying to figure out the best way to model the sphere-spiral here:

Is it possible to make this shape directly? Or do you have to make it as a cylinder and wrap it to a sphere?

The easiest way to model this is to shrinkwrap a strip of vertices to a sphere and then put a skin modifier on it.
I would recommend starting out with two verts, one at the origin and the other about twenty units up the x-axis and about two units up the z-axis. Once you have the verts in place, subdivide it with about 400 cuts and add a simple deform modifier. Switch the modifier to Bend mode and jack the angle way up to around 2560. This will give you a corkscrew shape.

Try to get it looking something like this. If you didn't quite get it right, you can set the transform pivot from Median Point to 3D Cursor in the bottom bar. Then, you can scale along the Z axis to make the corkscrew shape taller, or along the X axis to make it skinnier/fatter.
Then, make a new UV sphere subdivided a couple more times from the default and fit it inside the corkscrew shape you got, and add a Shrinkwrap modifier to the corkscrew. Set the mode to Nearest Surface Point (you can't use Project because there aren't any faces.)

At this point you will probably want to apply the simple deform modifier, go into edit mode, set the pivot to the 3d cursor, put the cursor on the bottom of the sphere, turn proportional editing on in Connected mode, set the falloff to sharp, and scale down the vertex on the bottom locking the Z axis. Do the same for the vertex on the top to get the shape kind of close to the sphere shape. (I recommend having the shrinkwrap modifier display on the edit cage to make this easier to see.)

Once you've done that, add the skin modifier, check Smooth Shading, and scale down the skin radius with CtrlA. Put a subdivision surface modifier on that and you've got your weird corkscrew sphere thing. Here's mine:

Hi, looks like you've got a decent answer going, but it's really hard to follow, and intimidating to read because of not having any line breaks. Could you clean it up a bit please?

Yeah sure, I'll get it done in a bit.

Here is a script to produce a Spherical Spiral  Loxodrome , from it's parametric equations
import bpy

from mathutils import Vector
from math import radians, sin, cos, tan, sqrt, floor

context = bpy.context

def loxodrome_points(spirals, revs, angle_step=10):
    a = 1 / spirals
    degs = floor(360 * revs / 2)
    segs = [radians(d) for d in range(-degs, degs, angle_step)]
    points = []
    for t in segs:
        den = sqrt(1 + a * a * t * t)
        x = cos(t) / den
        y = sin(t) / den
        z = - a * t / den
        l = Vector((x, y, z))
        points.append(l)
    return points

points = loxodrome_points(10, 10)
#loxodrome = bpy.data.objects.get("Loxodrome")
#if loxodrome is None:
if True:
    loxocurve = bpy.data.curves.new("loxo", 'CURVE')
    loxocurve.dimensions = '3D'
    loxocurve.resolution_u = 2
    spline = loxocurve.splines.new('NURBS')
    spline.points.add(count=len(points) - 1)

    for i, bp in enumerate(spline.points):
        x, y, z = points[i]
        bp.co = (x, y, z, 1)

    loxodrome = bpy.data.objects.new("Loxodrome", loxocurve)
    context.collection.objects.link(loxodrome)

Produces a unit radius curve  Loxodrome at (0, 0, 0) applying the matrix_world of a sphere to the loxodrome curve should see it remain on surface.  Adjust the parameters in loxodrome_points(10, 10) for differing 'dromes.

How can I scale the spiral or make it bigger?

A variety of spirals can be constructed. Equal width (involute), great circles and so on.
The Loxodrome on sphere pictured below is made with above equation on Mathematica, angle $\alpha$ between loxodrome and longitude is a constant. $ (r,\theta,z)$ are in polar coordinates.The arc line is thickened.

What's this supposed to mean? Was this meant to be a comment?

Please add some information as to how the user might be able to use this information. As it is, it is not clear how a user might implement this equation.

Added to my answer re that the Spherical Spiral is a special case of a loxodrome, in that the crossed meridians are those of a sphere.  Also added  link to wolfram page with equations used.

@Ray Mairlot I am very new to Blender. Equations of curves and surfaces  can be coded and shown in Mathematica.


text:
Rerending only freestyle on previous render
I'm playing with Freestyle in Cycles. I'm tweaking setting and rerendering. I'm spending a lot of computing time rerendering stuff expensive stuff, then doing a quick freestyle pass with new settings.
Is there a way to keep the "main" Cycles render, and only rerender the freestyle pass?

If what you want to change in freestyle can also be changed via the compositor, the following approach may also be useful to you:
Since Blender 2.83 there is an option to set Freestyle as a render pass in "View Layer Properties". After you have activated this option, there is a dedicated "freestyle" layer in the compositor.
This is also described in this answer

You can create two separate render layers and use one for the actual render, and the second one exclusively for the Freestyle strokes.
Combine them in the compositor and then update only the freestyle layer when you tweak settings.
Procedure described in detail here Adjusting Freestyle in the Blender compositor


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Can I color a curve in Cycles by the direction it's running?
I'd like to colour a beveled curve in Cycles by its tangent (the tangent of the actual curve - not its beveled faces).
For example:

In this image, the curves running up/down are blue, and the left/right curves are green. Is this information accessible in Cycles?

care to share a small sample blend ? :)

I don't actually have a good blend yet - I still need to write the script to import the fiber tracts. Will hopefully get to that in the next few days.

Alas, my laptop is I'd fried :( Time do do some research on the best choice for new hardware!

There might be a way to do this using using the Texture Coordinate node... near the bottom there is a text field where you can use another object to control the texture space... an empty for example or a flat plane with a texture map with a full range of colors perhaps...

@zeffii I have a sample blend, but it's impractically large - 334,000 vertices in my curve object. Turns into 23.4 million Tris after beveling :/ I can share if you like.

@ajwood, I'm trying to render tractography results using Blender myself, have you made any progress?

@DanielBlezek not really.. I've been thinking that using a hair particle system would make more sense than beveled curves, in terms of resource efficiency. I never figured out though how well the hairs will be able to represent the tracts though. If you figure something out, I'd love to hear about it!

This is totally possible with the Tangent node (Input > Tangent):

Change the type from Radial to UV Map and also enable Use UV for mapping in Curve's data tab:

The problem is we get black instead of Z-axis direction. That's easily fixable - add both green and red channels together and invert them into a blue channel. To also not care about the direction of axis we make the tangent vector values absolute:

This looks really promising! My context doesn't care about the sign of the tangent though.. so up-pointing-down should look the same as down-pointing-up. I suppose I could take the absolute value of the tangent vector. Can you think of the best way to make it note care about the sign of the tangent, without throwing out half of the colour space?

Think I may have figured out a way. If you enable "use UV for mapping" you'll copy the curve U/V coords to the UV map of the beveled object.

You can then use the vector transform node to strip off the object transform:

AFAIK this will fail if any of the curves have been transformed in edit mode since it relies on the object transform to get the coords back to world space.
Not sure if this is the best way, but I think any solution would have to be based around the "Use UV for Mapping" function as I don't think Cycles has access to the path itself, just the beveled and tessellated output mesh.

Don't fully follow yet, but looks interesting! ...I'm wondering, would this get easier if I dropped the Cycles restriction?

@ajwood UV's on itself are useless. There has to be math done with normal and tangent vectors from geometry node to get the actual spacial orientation of the surface. If Cycles cannot do it then there might be solution involving converting the curves into mesh and assigning vertex colors with script.

authors: Милен Мавродиев


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Get a path taken by a particle
Is it possible to convert a baked particle system to a curve (or set of curves) representing the path taken by each of the particle?

Use the Btrace addon.

It allows you to trace particles and to also convert the paths to curves.

I'm using 2.76 and the only "Add Curve" add-ons I have available are Extra Objects, IvyGen, Sapling, and Simplify Curves..

@ajwood Corrected. This is bummer, it was bundled I believe. And awesome addon. I hope it still works.

I downloaded it and seems to work so far!


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Can we execute custom Python functions from driver expressions?
I have a simple function that I'd like to call from a driver Python expression.

I've run the script to define the function, but it doesn't seem to be accessible from the driver expression.
Error in Driver: The following Python expression failed:
    'myDriverFunction()'

Traceback (most recent call last):
  File "<bpy driver>", line 1, in <module>
NameError: name 'myDriverFunction' is not defined

Is it possible to modify the namespace in which drivers execute?

you have to append it to the driver name space

see this http://blender.stackexchange.com/questions/27053/how-to-create-a-pydriver-in-blender-2-7

Your custom driver must add itself to the list of drivers BPY is aware of.
See the example here:
https://docs.blender.org/manual/en/dev/animation/drivers/workflow_examples.html#driver-namespace
import bpy

def driverFunc(val):

    return val * val    # return val squared

bpy.app.driver_namespace['driverFunc'] = driverFunc    # add function to driver_namespace

Also be sure to run the script to have it apply.


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Maximizing distribution of an object on a mesh surface
I'm trying to distribute a large number of shapes onto a mesh surface. I found a command in blender that does this, but it only allows me to place one shape on each vertex/face. I would need to add many more of them.
Is there are a command in blender that will distribute the maximal possible density of a given shape onto the surface area of a spherical mesh?

You could try a particle system, but how well it will work depends on what you mean by "maximal possible density". Could you elaborate?

Yes, so basically I am trying to distribute the maximum number of very small pyramids onto the surface of a sphere. So, for example, if I had a surface area of 500 um^2, I would want blender to fit the highest number of tiny pyramids into that surface area that is physically possible without any overlap.

This sounds like a non-trivial analytic geometry problem.  After you find an algorithm that will compute the placements for these shapes, then I (and any other python coders) can help you turn those placements into blender meshes.  http://en.wikipedia.org/wiki/Circle_packing#Packings_on_the_sphere


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Tesselate a plane
So I'm looking for an easy way to tessellate a plane in blender, where the centre of the plane has a lot of detail (tris/quads) while the edges have very little with detail being interpolated in between.
Is it possible to do this solely in blender or will I have to write a script to implement it?

do you mean remesh to triangles ?

Did you try that with remesh modifier using weight paint as a vertex group?

@Chebhou & Denis No I haven't tried that

@Soapy do you want to keep the original points ?

@Soapy I mean decimate modifier.

@Denis no but decimate is looking good...

@Chebhou no, just as long as it stays as a plane

Related: http://blender.stackexchange.com/q/5136/599

You can do that with decimate modifier using vertex group.
Create a plane, switch to Edit Mode and hit W button, then from the menu select Subdivide and in operator panel change number of subdivision to 100.

Switch to Weight Paint Mode, select Weight Gradient and start painting from the center out in one stroke.

Then in Weight Gradient operator panel or by using F6 button change Type to Radial.

Switch back to edit mode, add Decimate Modifier and in Vertex Group name select group that was created by the weight paint.

Then change the parameters of the modifier to get desired result.

Ha, just did this myself, but only thanks to you comments!


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Why my texture is not the same in blender and when i export collada?
I don't know why, i try everything after a bake to put my texture instead of the old one. The only way i see my old texture is in the outliner but i don't know why it's there because in my shader the only texture i have is the baked one...

I'm trying to get a baked texture to export in collada for playing with webgl after but this is really hard to get.

The reason is that you're using cycles. Save the texture you baked to a file and use it as a texture in a Blender Internal material, and the export should work. I export from BI to Collada for use in web and game engines all the time and it works nicely.
Related to this question: Why does the collada exporter not export texture references?

thank you it works now.
That's sad that we have to use BI for using the cycles baking in collada, all i do is a simple diffuse material, not very complex :(


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blender is crashing while rendering fluid simulation
I am trying to render a fluid simulation in cycles but after 5 frames my gpu drivers get reset, and the blender window becomes white and crashes, or not responding for hours.
my specs
cpu intel i 3 7100
gpu rx 590 8 gb
ram hyper x 8 gb 2400 mhz
I tried every resolution and samples, but it happens when I use gpu. Cpu rendering is stable, i have log file but i dont know how to post it
Render settings

Preferences

in the bottom of the image is the blender window became white and task manager

Try with Command Line Rendering. It tends to be more stable and faster than normal rendering. Here is a video with explanation on how to do it. It is easy, there isn't much to mess up there if you follow the instructions.
Shortly said, rendering in the Command prompt (CMD) is opening blender in the background, without having it actually opened. When Blender is open, it has to keep the 3d view and much more stuff loaded. But when you run it through CMD, you make it to load only the operation you need it to do.
How to do it
1. Open CMD - In the Windows search bar simply type "Cmd", and open it. It doesnt matter if you open it as administrator or not.
2. Locate the blender .exe file - The easiest way it to use the desktop shortcut, by right clicking  on it --> Open File Location, but can be done from Windows start menu. The copy it and go back to CMD.
3.  Set the working directory of the prompt - In CMD, type cd <blender.exe folder>. Usually its in Program Files --> Blender Foundation --> Blender <version>, but it may vary.
4. Do the magic - What you have to do now is to run blender.exe, but with special settings. One thing to note, the settings are just one letter, like -a, followed by specification. There is a space between the setting and the specification.
First, start by typing blender.exe(dont run yet). This will open blender normally when executed.
Then, add the special settings. At first, you need to specify which project will be rendered - i.e the location of the .blend file. So, to what you have written, add -b- this the option, specifying the location of the file. After it, add the location. So, you should have blender.exe -b <location of .blend file> Dont run yet.
Now, you need to specify which frame are you rendering.
For a still image, you use -f, followed by the frame number - -f <number>.
For animation, you use -s for the start frame, -e for the end frame, and then you add -a to tell the program that you are rendering an animation- -s <number> -e <number> -a
Additionally, you can specify an output location, but thats not really necessary, if you have one in the file. Use -o for it, followed by the output folder.
Now, you should be left with something like this:
blender.exe -b <.blend loc.> -f <rendered frame num.>
or
blender.exe -b <.blend loc.> -s <start frame num.> -e <end frame num.> -a
All you got to do now is to run this command. It shows the progress in the CMD. One really cool thing about it, is that you can actually pause it, even on one frame renders. Just click Pause Break button on the keyboard while the CMD window is active. To resume, click it again However, the render gets somehow slower after resuming, so i dont recommend this.
Thats all you really need to know about it, and even if it doesnt apply for that project, its really good to know it for the future.


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Darker Edges on my mesh that mess up my Subdivide mod
I have a Deformed Cone object.
I have extruded it (part that sticks out on the left). The rest of the mesh, including the other extrusion, is fine for the most part but this just looks horrid.
Lines / Creases that mess up my Sub divide mod:

In the mesh these show up as darker edges. I am wondering how I get rid of this so my object looks nice and smooth under the modifier.
Image of the object's Mesh

Image of the entire object

It's worth noting that I have tried to merge by location but the option to merge does not show up, I also checked my normals.
Is this just an issue with the placement of my vertices?

Please show your work in wire frame mode as well.  Make sure you have smooth shading. Make sure you do not have coincident edges. (Failed extrusions can cause this)You should look at how many corners have 5 edges and how many corners have 4.  Some 5 poles are necessary and the result of extrusion.  Make sure you do not have unnecessary  5 poles. Try not to get quads in the that look like long triangles You can search for Model Topology for lengthy explanations.

Archive your file or scene if necessary. If the original mesh has a small time investment then   try a second time. The second time may have reduced mistakes.  Fresh Start.

@atomicbezierslinger by going through each stage of your answer I fixed my problem, thank you. It turns out the problem was making a quad out of a neccessary 5 pole.

@FinleyQuayle if you solved the issue, please write an answer to your own questsion and explain clearly what you did. Other users with similar issues can learn from you.

@FinleyQuayle its always interesting when someone tells you to post an answer ... yet they have provided no candidate help or ... upvoted you.  Though mathematically I do not know that with certainty. Yet at the time of this writing you have 15 view.  I do not need an answer from you but if you are finished with this task I might want to have a reminder.  The choice is entirely yours.


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Weight painting / vertex groups questions
I have a bear mesh that is the combination of meshes from different files/different “versions” of this bear. Some parts of the mesh are disconnected/overlapping.
I have tried different armatures on this mesh and am now trying to use a “basic human meta-rig” to control the mesh. My questions are about how vertex groups in this mesh are working. In the “vertex groups” section, I do not know how all of the groups got there: are they from past armatures related to the same mesh? Are they from libraries that are shared across different meshes/files?
The basic human meta-rig did a good job controlling the mesh but had a few weight-painting issues. Because this vertex groups list was disorganized and I could not quickly navigate through it for weight painting I decided to delete all vertex groups and re-parent the basic human meta-rig. (However, it seems to me that entering weight paint mode with the armature selected, then shift-clicking bones, is a more efficient way to do this - do you agree?)
After deleting all vertex groups and re-parenting the basic human meta-rig, it did a much worse job controlling the mesh. I needed to go back to using the mesh with its disorganized list of vertex groups to get the meta-rig to work again. This made me think that somehow the meta-rig was working with previous vertex groups. Is this correct, or am I missing something?
Finally, I tried a different version where I used a basic human meta-rig and corrected all weight painting issues. In pose mode, the armature controlled the mesh exactly how I wanted it. Then I clicked “generate rig” and parented the mesh to the rig, went to pose mode, and found that the rig’s control didn’t correspond to the meta-rig armature’s control. Why is this?
In general, do you think that using a meta-rig the most efficient way to control a mesh like this? I would like to be able to easily animate simple movement - walk/run, dance, sit, swim, etc. I will appreciate any insights on how to better animate and understand these concepts. Thank you.
LINK TO FILE:

You should follow some tutorials on rigging, like Darrin Lile's or Sebastian Lague's, it's better to first learn from scratch in my opinion.
Before parenting it's always better to make sure that the transforms (scale, rotation) have been applied, and that the normals of your mesh are correctly flipped.
For the vertex groups, when you'll parent the mesh to the armature With Automatic Weight, it will automatically create as many groups as you have bones, and the groups will have the names of the bones that control them. If the mesh already has some vertex groups from previous operations, it will keep them as long as their names are different but it won't interact with the parenting, so you should not have to care about that but you can always delete them if you prefer.
If you parent With Empty Groups, it will create as many groups as you have bones, but it won't affect any vertex to these groups, you'll need to do it either with the Assign button or in Weight Paint mode, this is the best method when you parent non organic objects like machine, robot, etc. as it let you define what part is supposed to be controlled by which bone and doesn't create any gradient influence.
For the armature, you can use the ones you currently have, except it seems incomplete, you should have a root bone, your lower legs or lower arms should have IK constraints, you should have the targets and pole targets for these constraints (you already have targets for your legs though), and make sure that these bones (root, targets, pole targets) have their Deform options disabled (which is not the case for your leg targets).


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How to get mouse position in a window with Python?
I want to detect if the mouse is in certain area of the 3d View, so I can display a custom menu when it will be in the left top corner, over the view name ("User Persp" etc).

Take a look at the python templates, some of them use the mouse position, such as the Modal Draw template that draws the path of mouse: http://i.imgur.com/55rYdAc.png

Here is a script from the blender wiki.
Go to the Invoke versus execute section for finding this code:
#----------------------------------------------------------
# File invoke.py
# from API documentation
#----------------------------------------------------------

import bpy

class SimpleMouseOperator(bpy.types.Operator):
    """ This operator shows the mouse location,
        this string is used for the tooltip and API docs
    """
    bl_idname = "wm.mouse_position"
    bl_label = "Mouse location"

    x: bpy.props.IntProperty()
    y: bpy.props.IntProperty()

    def execute(self, context):
        # rather then printing, use the report function,
        # this way the message appears in the header,
        self.report({'INFO'}, "Mouse coords are %d %d" % (self.x, self.y))
        return {'FINISHED'}

    def invoke(self, context, event):
        self.x = event.mouse_x
        self.y = event.mouse_y
        return self.execute(context)

#
#    Panel in tools region
#
class MousePanel(bpy.types.Panel):
    bl_label = "Mouse"
    bl_space_type = "VIEW_3D"
    bl_region_type = "TOOL_PROPS"

    def draw(self, context):
        self.layout.operator("wm.mouse_position")

#
#   Registration
#   Not really necessary to register the class, because this happens
#   automatically when the module is registered. OTOH, it does not hurt either.
bpy.utils.register_class(SimpleMouseOperator)
bpy.utils.register_module(__name__)

# Automatically display mouse position on startup
bpy.ops.wm.mouse_position('INVOKE_DEFAULT')

# Another test call, this time call execute() directly with pre-defined settings.
#bpy.ops.wm.mouse_position('EXEC_DEFAULT', x=20, y=66)

Now if you want to know the position of your 3D view, I made a quick research. With this you can find the area of your 3D View:
import bpy

for area in bpy.context.screen.areas:
    if area.type=='VIEW_3D':
        X= area.x
        Y= area.y
        WIDTH=area.width
        HEIGHT=area.height

        print(X,Y,WIDTH,HEIGHT)

Thanks, now I guess I need to get the position and size of the 3d View, to determine if the mouse is in the specified location or not. The sidebar also adds trouble.

I've edited my answer. At the end you will find how to determine the size and position of the 3D View.

That's great, works, thanks! Any way to determine the sidebar current width? If I can get that, I will be able to do what I want.

I don't know how to determinate that. Ask it at an other question, you will find better help :)

You get the area and the region from the context
argument (passed to the invoke / execute / poll method of the operator).
Use the operator's poll
method to check for the right context. I.e:
@classmethod
def poll(cls, context):
    return context.area.type   == 'VIEW_3D' and \
           context.region.type == 'WINDOW'

Just want to add:

The event class
also provides the attributes
mouse_region_x
and
mouse_region_y
The view2d class
provides methods to convert mouse coordinates from region coordinates to view coordinates
The bpy_extras.view3d_utils
module provides methods to deal with 3d-coordinates

Do you mean poll for the operator or the panel?


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Can I choose when animation in animated dupli-groups starts?
I'd like to use some sort of re-usable animations (think little animated effects, simple but a lot of them), that I can play during my main animation, without creating multiple actions, or having multiple nla blocks. I was thinking that animated dupli-groups would be ideal. But can I choose when animation in animated dupli-groups starts? If not, then this way clearly won't work.

Currently this isn't supported
This used to be supported (in 2.49), using the Time Offset field on the empty object instancing the dupli-group.
However support for this is planned. One of the goals for having an improved dependency graph (currently in development), is to have local time for group instances.


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How to access now rendering object from a driver into a material node property?
When defining drivers for Material Node properties, self references the Node itself. While this may have its uses, it would be great to be able to access the object being rendered. This way you can create a single material that produces correct results for a batch of similar objects, all linking to that same material.
I'm in a situation were I had to create 40 copies of an object, all having 2 custom properties of type float. Those 2 properties are meant to control a driver defined in a material node.
The problem: that I needed to create 40 copies of the same material, reference the correct material from the correct object, and edit all drivers to change the object's name.
The process of going into all objects to edit their material slots, to copy the previous one, then unlink the previous one, then go into node editor and edit all drivers only to change the object's name is very inefficient.

You don't need drivers if you're using a more recent version.
You can directly access object custom properties in the Shader Editor, using the Attribute node. Set the Type to Object and type out the name of your attribute.
Example :
Have an object with a color custom attribute named color and a float attribute named roughness.

Using 2 attributes node in the node tree :

Control values individually, with the same material.

As a bonus, check Is Library Override in the custom property.

In a new file, link the object, Right click on it in the hierarchy > Id Data > Make library override. You can now control linked objects' custom properties, and by extension their material.

Just perfect. Thank you. I'm switching to this method. Blender version is 2.93.


text:
Creating CMYK Printing Simulator/Shader
Out of curiosity, I wanted to see if I could develop a quick little CMYK print shader in cycles. So that I could plug different images in to the shader and have it display as if it had been physically halftone printed. Very similar to an RGB screen shader I've seen before that separated the RGB colors and put them back together as pixels/cells...
Below is the basic set up I've started with, but am curious if anyone out there has more experience with printing that could offer any advice to get something closer to a realistic result? As I'm already certain that just separating R->M G->Y B->C is not the actual correct way of doing this, just thought I'd start with that to see if it actually did anything.

Would love to hear any input :)
Thanks!

I guess maybe related.. https://blender.stackexchange.com/questions/102352/blender-halftone-pattern-filter

Compositor has a separate YCbCr node.  I dunno if that's relevant, just tossing it out there.

https://blender.stackexchange.com/questions/99409/how-to-use-halftone-python-shader-node and https://blender.stackexchange.com/questions/175575/creating-this-halftone-effect-using-arrays and https://blender.stackexchange.com/questions/168636/tapering-textures-with-nodes/168642#168642

Yeah I strugged with the making a cmyk simulator to but I stumb across this tutorial on reddit by Gwirk
He went through the process on how to make a half-tone
It pretty much goes like this
Step 1: Offset each color value by -1
generate your color negative channels
this will invert it the color and give us the cyan ,magenta ,yellow color we need
The problem now is that we have the black data mix up with the color data

Step 2: Grab the min value of all the color channel
generate your K/black channel
this will be your K or black value ,and will also help in removing the black data from your color info
K = min(R 1 ,G 1 ,B 1 )

generate your K/black negative channel:
This is the same operation as in step 1 but instead you'll be substituting color with K
K 1 = K - 1

Step 3: Remove the black from the color channel
You'll have to offset the color channel by your black channel
you're just subtracting K from your colors
R 2=R 1- K
B 2=B 1- K
G 2=G 1- K
Then divide by your black negative channel
R 3=R 2/ K1
B 3=B 2/ K1
G 3=G 2/ K1

The next part is to convert it back to rgb
This this simpler as you’re just undoing the conversion you did in the previous section
Just multiply your color channel by a negative version of the black channel
and then add back the black channel you removed

don't forget to undo the offsetting you done to each color channel
sorry about the small image
here's a colored aided

all that's left is to plugin halftone shader of choice.
this part is a creative step so I'm not going to describe. how to do just going to link to a bunch of halftone shader tutorials instead
https://www.youtube.com/watch?v=li2mSnKY194
https://www.youtube.com/watch?v=vnLJmqiBDXI
https://www.youtube.com/watch?v=KjQ37vFLotk
https://www.youtube.com/watch?v=Go8ivK00Y-A
https://www.youtube.com/watch?v=Z-1w4pYdUNQ
https://www.youtube.com/watch?v=dRP1DqShceM

half - tone generator by the original poster of the tutorial on reddit

down below is a article that explains everything better than I can
https://bensimonds.com/2013/02/14/halftone-shader/


text:
Black part when glass touches a surface
I've modeled a glass container with a very simple principled shader (see below).

When the container is in contact with the floor, the lower part of the container turns black. (cycles render)

How can I fix this?


text:
Is it possible to pin distinct Bones of a Model to a Plane while posing?
I need several poses and would like to know if whether it would be possible to pin the feet or hands of a model to a plane (as floor or wall) while animating excercises like squat or push-up ?
If IK would be the answer: Setting an inverse kinematic constraint usually allows me to move the legs by moving a foot, but I want it the other way around. I used rigify and I'm still intimidated by the complexity of this rig, how should I setup the IK chain (without breaking it) ?

A meta-rig created by Rigify is set to forward kinematics by default. With the settings shown in the n-panel on rig-foot.ik.L/R it possible to move the body with the foot on floor by only moving the rig torso (shown in 2nd img).

Naturally, that is how inverse kinematics works. Blender also has an auto ik feature, look for it in the N panel when in pose mode. You can use this to quickly pose models without the need for any constraint setups. I would also recommend that you try creating your own rigs in the future, it is a very rewarding process, even more so if you make it switchable..

@iKlsR Thanks for your response again, I really had a hard time to understand the rig so far. I will probably come up with more questions. I've done my one rig first but it was painful to keyframe without widgets (don't know how drivers for bones are called) rigify introduces another quality of complexity and I haven't found a decent documentation. Do you have a link?

I really wouldn't recommend rigify to a beginner, it is a very complicated rig. However, cgtuts's blender category be of some help to you.

@iKlsR Ouch I totally missed the point, after watching this one (although for maya) http://www.youtube.com/watch?v=pGuR4xyi7MQ I understood the diffference between IK/FK. Thanks for the link I already watched some of them.