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Box Mapping on just X & Y Axis
I'm box mapping a grunge map to add dirt to the bottom of some assets which works great....except it is projected on the z axis as too.
Is there a simple way toto just project on X & Y that I'm missing?

Maybe create a new UV map and use it into a UV Map node before this texture?

Hello :). Just to be sure - you only want the texture projected on vertical faces, but not on the top/bottom faces?

Not just the vertical faces since that would skip some lower but upward facing edges.

Are you sure you want to just project in X+Y?  Notice that the beams on your top have some faces pointing in X+Y.  Do you want to limit by direction, or by position?  If position, you need to paint a mask texture to specify where you want the grunge.  If direction, it's doable in nodes (after you explain what you want.)

This is easier/smarter to do with a procedural texture for the dirt, but I got it to work.

I used Texture Coordinates>Normal>Separate RGB and plugged the Blue into a color ramp to get all the upward faces.
I mixed that using Mix RGB>Multiply with a Gradient Texture, rotated 90 degrees on the y axis.
Together, these make a top to bottom gradient mask that ignores only the very top upward faces.

Little more complicated that I wanted, but maybe useful for texture layering.


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How to apply Cycles modifier in Graph Editor?

Let's say That I need to repeat current keyframes 20 times (it is not a "static" loop, as You can see: there is an offset! (NLA won't work in that case)) and in 20'th copy of the keyframes I would like to change something. So I need to apply the modifier.
It is important becouse I want to export the animation to external programs, so I can not leave this with active modifier: I need real keyframes.
Second thing: I know that there is a "Bake Action" option, but I don't want to generate different keyframes that the only ones that I really need.
So is there any way to apply the "Cycles" modifier in Graph Editor ??? Or do I really need to copy and place keyframes by myself?

What you're looking for is keyframe baking, which does exist. There are two baking operators on animation curves: bake curve and bake action. What you want to use is bake action. They are both terrible operations, in my opinion, but they get the basic job done... I will explain why later.
Select the object or bone in question and take note of the distance between your cycled keyframes (in my example I used 22). Make sure your curves are editable and do a spacebar search for "bake action." This will pop up an option window.

Set your start and end frames accordingly, then change the frame step to the distance between your keyframes (22 here). Click OK and your action will be baked. If you leave "Overwrite current action" unchecked, it will automatically add and activate a new action for the object/bone. This is basically what you're asking for, but here are some snafus:

Tangents are destroyed

This is my biggest pet peeve of this operation. So you spent some time scaling your tangents to get the right kind of curve and cycled it. Great, now you want to edit the positions of some of those keys. Well, too bad, because baking destroys tangents. It will automatically set tangent types to automatic. Again, this totally destroys your work and takes control away from the artist. The only case where this is OK is when all your tangents are completely flat and automatically weighted. Then all you have to do is select all, change pivots to individual centers and scale to 0 on Y. It's a terrible solution.

All channels are baked simultaneously

This would be fine if you're doing pose-to-pose keying, where all keys are aligned to the same frames, but totally useless if you have offset curves.

Automatically cleans keys

Automatically cleaning keys is bad because you want keys on each bake step, so this is not expected or appropriate behavior.

"Bake curve" locks curve from all editing

Obviously locking the curve is out of the question.
You should try both baking operations to see for yourself what they do. They're pretty nasty if you ask me. Unfortunately, these are the only two options I could find.

Thanks for response. As far as I could understand your post, your solution will work if you have animation based on keyframes that are placed beetwen eachother in the same amount of keyframes (in your case it was 22).
But my animation is based on few keyframes, and there are different amount of spaces between those keyframes.
Please write back: is your solution work in my case?

Well... I kind of found out work around to solve that problem but it is so ridiculous!
It is only going to work on single animation channels (so you need to redo this steps).
First you need to find out what is the difference (in X and Y positions of keyframes on the graph) beetwen first and last keyframe of the cycle. Then You copy them, but it is not possible to speciffic precisly Y coordinate, so you can leave new copy of keyframes whatever and than you hit F6 button to specify precisly the offset.
Then you hit SHIFT + R button to redo copying with precise offset.
Any better solution? :((

I wish there was. I can't think of anything off the top of my head. I can play with baking more, but I won't hold my breath.

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How to edit curve, but not ruined tilt settings?

Here I have Roller Coaster set up correctly, but let's move only one random handle and let's look how the whole roller coaster set up is getting ruined.

Everything is ruined, do I really need to set again every tilt for every handle again? And If I again will need to change something, Will I have to change tilt everywhere again?
Help please ; (

What is the curve twisting mode set to?

Minimum. Is there a lot of difference  between those options?

I'm not a big fan of curve modeling, but in general whenever I see this weird things happening, I always make sure to apply scale for both curve and path, and always use Ctrl + T to control tilt in Control Points, do not use Rotate.

Check that proportional editing is disabled.

This behavior is crazy and should be treated as a bug in my opinion...

I think you might want to change tilting to Z-Up under the Properties Window > Object Data Tab > Shape Panel
Although it is not perfect it will probably be the closest to a correct "always up" tilt. You can then manually adjust whichever parts are not supposed to point up, which I believe are probably a minority compared to the tilting curves.
From my admittedly limited testing with Z-Up changing other parts of the curve has no effect on the already established tilts

I tried to do so, but the problem was when the Roller Coaster was drivin' straight down and doing spiral at the same time (You can not see it from the Top View). So I think that for now, I need to do adjust tilts by hand every time I change position of any handle, which is really a big pain in the A.

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How to set distance of Freestyle line rendering?
I would like to have thicker lines near camera and a lot of thinner in some range of distance from camera.
How can I achive this?
I tried 'Distance from camera' modifier (I tested all settings. Including "Invert" checkbox) and the only results I'm getting is the opposit effect: thicker lines far from camera and thinner near camera.

What should I do?

The Distance modifier scope is to control the line's thickness with its distance from camera. The main parameters are four:

Range Min: the distance of the camera's nearest object from the camera itself
Range Max: the distance of the camera's fartest object from the camera itself
Value Min: the bottom value of the graph
Value Max: the top value of the graph

The values
Notice that I'm talking about the graph and not the resulting thickness (that is the curve itself) because I would like to suggest that is not a good idea to set a Max value lower than the Min value.
The values should be defined in order to set up the graph (if you choose Linear insead of Curve you are just forcing the curve to be straight, but the concept is the same), then you can tweak the curve to get the desired result.
The range
To quickly get the correct Range Min&Max value you can use the built-in function Fill range by selection. Basilcally you'll just have to pick two object, push the button and you'll automatically have the fields filled up.

Once the four parameters are set up, you can focus on defining the curve. In your case you should draw a top to down strahight curve to get higher values at the beginning of the range and lower at its the end as shown in the image above.

If you would like to use the Linear option, you should activate the invert option in order to flip the straight curve.

Conclusions:
Start from filling the four parametrs with appropriate values.
In your case you left the default Range parameters (0-1000). I can't see the scale of your model, but I can guess that they are not appropriate. Give it a check.
Start from using very different Min Max values (e.g 1-50) to see the effect clearly and then lower them once you are sure that all works...
...and make sure the modifier is ENABLED FOR RENDER or you'll not see any of its cool effects! :)


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How to increase precision of color ramp affecting model?
I created color ramp with 10 colors. Every color point has typed position as multiplication of 10%. Values are: 0.1, 0.2, 0.3 and so on.

The plane was divided 9 times, so the results are: 10 faces with the exact same size.

The colors don't appear on a model precisly.
Typing 0.6 at the blue color point position don't make blue color appear on model at exacly 60% objects width - it gives close representation, but it is the same final result on model as typing 0.598 or 0.601.

I want my color ramp to have higher precision representation on model. How to change that?

Probably an issue with the origin location. This is not enough information to solve it outright through. But try moving your object in edit mode. uploading the blend file is the best way for help.

Color Ramp is implemented with a 256x1 texture, so you can replace it with your own texture of whatever width you want.

It is a known issue, ColorRamp marker positions are rounded to the next higher multiple of 1/256, leading to unexpected output, especially when set to 'Constant' interpolation. There is nothing you can do about it except adding burninate token here:
https://developer.blender.org/T74198
If you want to be precise, you should switch to math nodes:

It depends what you need, but it could be as simple as this ..

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How to change curve type?
I've created a bezier curve but now I want to change its type to path.
How to achieve this?
And btw. if I can animate both: bezier curve and path, what is the practical difference between those?

Okay, so there are two main kinds of curves in Blender. Bézier and NURBS. A path is a NURBS curve and you want to convert a bezier curve to it. To do this is really easy:

Click on the bezier curve in question.
Press Tab
Select the bezier curve by pressing A
Press Space and search for "Set Spline Type"
Click "NURBS"

Now you have a "path" or NURBS curve to work with. I found this solution in reverse on here.
As for the practical difference between the two, as far as i can tell, the NURBS curve is more accurate and precise than its bezier counterpart. I hope this helps.


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Why constraints ruins material set up?
I'm creating a scene with planets, and I wanted one planet to track to the camera (but not in 100% percent). But when I want to render it the "fresnel node" is acting weird. Why constraints ruined my set up, and how to avoid this?
Of course I want planet to rotate in directon of my camera, but fresnel must behave the same as before (it should outlines the object, not creating some line via center of object). I tried different constaint settings, nothing worked.
Simpler Example (both screens are from camera perspective):

Hi is it possible to save an e.g blend file with just one of your planet in question so we could look at it closely?

The solution is to disconnect the normal input connected to the fresnel node.
The cause is the order that things get calculated. In your example the normal value is calculated to fulfil the material needs, then the constraint is applied and the result is sent to be rendered. Without the normal input, cycles uses the normals of the object during the render, which means the normals are calculated after the constraint is applied.


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Multiple Curve Guides act wird
I have set up Curve Guide. It will be used for showing how particles are moving inside of pipe.

The particles need to be insisde of 'pipe' object, so I thought that the best particles behaviour would be achived by Curve guides, as particles are good girls in this scenario and they don't fly away or something like that .
The set up works wonderful until I don't Duplicate Collection to create another CurveGuide System... Particles are being 'distracted' by the close Curve Guides...

In final animation the particles in the pipes will be close to eachother, and each particle system needs to be inside of his 'pipe object', it will be something around 36 pipes. The pipes will be slightly different so instance copy won't work.
How to set up these Curve Guides to only effect one particle system for one Curve Guide?

Ok, I found the option. We need to "Use Max" (Curves' Force settings) in this kind of situation (for all Guide Curves in the scene) :)


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How to hide light overlay in viewport, but keep visability of lightness, curves and camera in the viewport?
I know that I can hide light objects by: "Viewport Overlays / Objects / Extras", but it is hiding camera objects too! :(
In my project I have many lights, and now, when I'm done with lighting of the scene, I want to work on camera animation, but the light objects overlays make that very inconvenient.
Is there a way to see in viewport camera objects, curve objects, mesh objects, but not light objects (but keep the lightness)?

The general solution to this is just to hide the blocking objects regularly (with H), and work in material preview mode or solid mode. Will this not work for you?

No, it is not the answer for the question, especially when you have dark scene lited up by many lights, and you are "hunting with camera" for best, cinematic speculars created by your lights. What about hiding all overlays (perhaps you'll say)? It wouldn't help either, especially if your camera is rigged, following curve and has empty as target.

Oh, I see! Yes, that would indeed require all the lights to be rendering . Sorry . Are you sure you cannot still go into camera view while the camera is hidden? One alternative would be to have two 3D viewports next to each other… I’m gonna see if the other guy’s answer fixed this. PS: it’s not lited, but rather “lit.”

Hey! Check out the Animate tab. There’s a camera aligned viewport in the corner that doesn’t show overlays somehow. Also, you can have two viewports next to each other, one with overlays in solid mode and one without in render mode, so you can see what you’re doing.

@TheLabCat Sorry about "lited" :) In complex scenes playback animation can be slower if you have 3D viewport opened few times, even in solid mode. Yes, I can go to camera view even if it's hidden, but I want to have empty (the target for the camera) shown, as well as paths. Thank you very much for all your trying, but I just wanted to know if there is an option to have rendered mode without lights overlays.

@vklidu Eevee. Baking is not an option when you're dealing with animated camera and speculars.

@evilferber Right ... seculars ... I'm going to delete my comments to clear it a bit here :)

I hope this is better: Another way I just found is to deselect the "Show overlays" button in the top right corner of the 3D-viewport window. Yes, you can't see the cameras :(, but when you want to see a specific camera or show keyframes or something like that, you can just select it in the "outliner" window (the one that has all the objects listed in it). Although this may be a little hard to work with, you still get your lighting and you can still see your cameras outlines when you select them.

I know all the stuff you wrote about. Won't work so well in my scenario.

I thought the same thing, but actually really needs full lighting, cuz he’s trying to get the camera position just right for a cinematic shot.


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How to set transparent property per object for fade in/out, without having redundancy of materials?
Before you comment:
I don't want to have 200 materials of the same metal just for fading out at different times.
Render layers are out of the question too of course.
I bolded it out because I found here several quite similar questions and almost everytime someone who doesn't understand the problem of redundancy in complex projects advise to have the same amount of materials as fading in/out objects in scene.

I am working on couple of animations where lot's of objects are needed to be fade in and out at different times.
Since the projects are quite complex to manage for me (and I already have plenty materials) it is not effective to, for example, have 200 different materials of the same metal just for fading them in/out at different keyframes.
Is there any way to do it using maybe Custom Propterties in object panel?
I've tried using drivers on Custom Properties, but it always fading out all object sharing the same material.

maybe Animation nodes are the way to go? Also, do you have to control when the fade out happens for each object or can it happen randomly?

The animations ment to be an explanation of how mechanical devices work. Timing is very important here, it can not be done randomly (as it can be done via particles however).

You can use object viewport color to have per-object fading information. You can keyframe the viewport color of any mesh object. See : https://blender.stackexchange.com/a/163699/86891

wow great, this Object Info color seems to be a new thing

So the answer is in this video:
https://www.youtube.com/watch?v=WWwS-0AHotY
Here it is how it can be done (in eevee too!):

Select an object (from outliner or 3d view, doesn't matter).
Go to the 'Object Properties'.
In "Custom Properties" panel click "New" (In my case "Custom Properties" Panel is at the top of all Object Properties Panels because I moved it - you may find 'Custom Properties' in your layout in different place)
Click the gear icon to configure your custom property.
The Pop Up will came out.
You can rename 'prop' to 'Alpha' or something else for better organisation of the project.
Click OK or Enter (if you click outside of the pop up panel, the panel will close without saving your settings).

Add 'Attribute' node in Shader Editor.
Change Type to Object, type name of your Custom Property (in my case: "Alpha").
Now every object with this material and with Custom Property "Alpha" (in my case) can have it's own value of the Alpha parameter of the shader. Custom Properties' values can be change in side panel. If you use Eevee be sure to change settings of Blend Mode of the material (I prefer "Alpha Blend").

You can use the object viewport color to force variation per-object, even if they share the same material.
The setup is quite simple :

If you are using Eevee, don't forget to tweak the blend mode and uncheck "Show Backface"

Add some keyframes and play :

Further reading on viewport color

Thank you very much :)

Little update:
Because the object color has 3 inputs that make difference in this soultion (Red, Green and Blue channel, the Alpha Channel is useless here), I also drivered these three inputs to Custom Propterty (called by me:)"Transparent". Now it is really easy to work with :) Thank you again <3

Objects with material's Blend Mode set up as: "Alpha Blend" are not being reflective in other surfaces. And their shadows aren't fading out... but just stay.
Not a perfect solution for everybody, but it will work for me, as I'm not aiming at photorealism in current projects.

Did you try Alpha Hashed ? I'm afraid this is a limitation of Eevee

I tried but that creates very specific effect that I do not want in my 'clean' 'technological' , so sort of "kickstarter animations".
I really hope that Blender Developers would figure that out one day <3.


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How to create simple Fade In effect with transparent material, but without rendering X-ray backfaces in Cycles
I'm working on an animation where lot of objects needs to fade in to the scene. I know that I could achieve it by rendering hundrends layers and passes and then spending hours an hours on composition, but I want to do this clean with just materials.
I need material with transparency in Cycles without any X-Ray or back faces effect

With Geometry -> Backfacing we can tell the shader to use a Transparent BSDF if the ray strikes the inside of the mesh.  This causes some noise that has to run a few samples to resolve (64 - 128 samples should be ok).

Ah... Totally forgot about back-facing. Anyways, nice answer.

@YousufChaudhry I like the fresnel answer, though

To my surprise : When I have multiple shapes, which are concave , the X-Ray Effect still exists in this solution. But in simple cases it is great :)

You have multiple shapes, which are concave, and what you write about compositing suggests that this is a problem for a much more complex scene that what you're showing us.  Backface culling, or anything related, isn't going to work here:

It will still give us your "x-ray effect" when we look through concavity, or we look through two meshes.  (It will also affect your shadows when you don't have manifold meshes, which is why these shadows look funny, but that's not a big deal in most situations.)
There is something we might be able to do that will work better:

Here, rather than using a Transparent BSDF to create my basic alpha, I'm using an IOR 1.0 Refraction BSDF.  That turns my rays into transmission rays, so I can make further hits, backface or frontface, this object or another, into full transparency.  To animate, I'd just be animating the mix factor from diffuse->refraction.
Refraction doesn't quite act right in Blender with regards to shadows, so we can improve this a bit by replacing our straight refraction BSDF with "ghetto glass": we'll mix between refraction and transparency on the basis of "is shadow ray":

This technique requires that you not be using refraction elsewhere in your scene, because these materials will be invisible to any kind of refraction rays, not just the rays they themselves generate.  Refraction is not necessarily a frequently used effect, so this might meet your needs.

A little tedious to do every time, but I would say, this is a very nice and detailed answer.

Instead of changing the alpha value, you could use a mix shader with a transparent BSDF and set a fresnel node to the factor:
You can tweak the IOR to differentiate between a solid and transparent look. As you can see, the backfaces are not visible now.

But how to control animation of opacity then? I want to animate opacity.

@evilferber just animate the value of the Fresnel node, press I and set it at 1 for solid, and set it to max and press I to keyframe at the Fresnel node's max value (something extremely high) for transparent.  Just like how you would animate the alpha value.

Looks great! Especially if someone wants flashy fade-in :)


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How to change Render Properties on multiple scenes at once?
I am using EEVEE. I have 36 scenes blended together in other scene (with just VideoSeqenceEditor) to get fade-in animations between collections (in one scene a collection is disabled, in other scene the collection is active, changing opacity of the second scene will give us fade in/out effect without unwanted X-Ray effect).

Now I want to work on visual aspect, but I don't know how I can change Ambient Occlusion values in Render Properties for all scenes - without need to enter each scene end change individual values of Ambient Occlusion.
How to do so?

maybe an add-on can do this or you write a python script


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What's the Benefit of Using Layer Weight?
I just don't see the difference using Facing and Fresnel, or Layer Weight as a whole in my node editor.
Is it a big difference using it, is it useful for distant objects?

related: http://blender.stackexchange.com/questions/29161/relation-between-fresnel-ior-and-layerweight-blend

There are many big differences, among which are that:

Fresnel depends on the face normals of your mesh - it will not work with inconsistent or incorrect normals;
The Layer Weight node allows for a smooth blend between the two;

Depending on what you wish to achieve, it may be better to use a specific one, but generally, you'll want to use the Fresnel node, as it's more physically accurate.

Is it effective when far away?

@BinaryGreen What, the Layer Weight? It should

@someonewithpc what do you mean by 'between the two' (2nd bullet point) could you add a link?

@stacker Between the two parts of the mask. Both ways generate, basically, a mask to use for controlling mix nodes - black and white - , but layer weight blends the white and the black parts, to give a smoother transition


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How to Add a Shader to a Specific Part/Area of an Object?
So let's say I create a material in Cycles and let's say, I load an image texture onto a sword. It perfectly fits, all good.
Now, the sword I would load in would only be one part, it's just one big mesh.
So how would I select an area of the sword, let's say one part would be steel, and the other part would be (leather)? I just need to know how to add more than one shader on different parts of the object.

You can assign a material to specific veryices

You could do something like this, to control where the two shaders go.

You can assign another material to the faces that should have a different shader. Just go into edit mode, select the faces that should have a different material and assign it to the face:

Otherwise you could mix two shaders depending on a texture:

And I can assign the material to more than one object or only just that face?

A material is a collection of shaders/other nodes that tells Blender how to render a specific surface. They can have as many users as needed, it doesn't change the material at all. So yes, you can assign the material to any number of objects, faces, or a mixture of the two.

When I loaded the sword in, it like, had all these crazy vertices and faces and what not.

Wouldn't selecting materials for specific faces just become known as Texturing, or is that different?

@BinaryGreen Texturing is assigning a color or value to a model depending on texture coordinates, which do not necessarily depend on the faces of your mesh. Textures are usually defined on a sub-face level and thus can help you change materials inside a face.


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Where did object dimensions go in 2.8?
Anyone seen this panel? Essential for precise modeling.


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Make an object invisible to a specific camera? (Cycles)
I'm trying to set up multiple cameras for a scene set in a room. Is there a way to link object visibility to a specific camera? Ideally, a wall or ceiling would not render if it were in the way of the specified camera.
I've tried to get around this by keyframing Restrict Rendering, but that gets difficult to keep track of. I've also tried adjusting the clipping plane, but that clips too much and would also need to be keyframed if the camera moves.
Thanks!

This is not possible as far as I know. Common workflow is to use several scenes instead, each with linked objects but different active cameras. Remove undesired objects on each one.

You can try to use Render Layers. Here's an example: https://www.youtube.com/watch?v=VUETvN-qtvk

This is possible using Drivers similar to the method described in the answer to How to change world background based on active camera?
You should set the Pass Index for each of the Camera objects so as to identify each camera.

Then add the driver to the visibility of the object being controlled - either the eye icon in the Outliner or the Camera icon - depending on whether you want to control the visibility only in the 3D view or in the final render.

Set the Driver expression to :
bpy.context.scene.camera.pass_index == n

Where 'n' is replaced with the pass_index of the camera from which you want that object to be hidden. Repeat for each object, specifying the relevant 'n' for each driver as appropriate.
Changing the active camera should now hide the object from view. Note that the driver will not necessarily update the visibility but will be updated on the next frame change - so animating the change in active camera on a specific frame will now automatically change the visibility of the objects.
Here I had 4 cameras positioned around the objects - with Pass Index of 1,2,3,4 - with the visibility of the objects (Cone, Cylinder, Torus, Icosphere) driven appropriately  and the active camera changing on each marker :

Brilliant! Works perfectly. Thanks for your help!

3 years later (2.9beta) this trick doesn't update the viewport but still works fine for renders

I can confirm that it still works in Blender 3.0 (and only for the render view). Another tip is if you want a particular object to show up only for a particular camera, just change it to: bpy.context.scene.camera.pass_index != n

Works for Render Visibility in Blender 3.2
!= tip by @Totomobile is helpful.


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how to UV unwrap a material
Is it possible to UV unwrap only a material? I have on object with multiple materials and I would like to apply a texture only to one of them.
Thanks for answers

I'm pretty sure you can unwrap only a mesh, because unwrapping is projecting 2D texture onto the 3D object. After unrwap is done you apply materials to a mesh to be able to aaply textures. Then to apply a texture to only one material you simply select adjacent material and add texture / texture node (depends on engine) only for it.

To clarify, you don't unwrap a texture, you unwrap a mesh. UV unwrapping is a way of defining the translation between a spot on a 3D object to a spot on a 2D image.
You can create multiple UV maps for an object and choose a specific UV map to use for a texture image. When you want to use more than one image for an object you don't have to use the same UV map for each image.
When UV unwrapping, the UV layout shown in the UV/Image Editor is the data associated with the UV map highlighted in the UV Map list. The UV map with a little camera next to it is the default layout that will be used if no specific UV map is chosen.

When using Blender Internal you choose the UV map to use in the Mapping panel of the texture settings.

For cycles instead of using a Texture Coordinate node, you add a UV map node and choose the UV map.


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still frame camera solve
I've found a number of how-tos for solving video but I'm just looking to put an element in a photo and can't seem to find a how-to for that.  Is it possible in blender to do a camera solve with a still image?  Thanks.

I don't think I get what you are asking . . . there isn't any parallax or rate of change ratios that can be compared to a constant like that. You shouldn't need it

In cinema 4d they have a camera calibrator tag where you can load an image for the camera and then draw lines that represent the x, y and z axis.  once you have a few lines drawn for each axis that follows lines in the photo you can select 2 lines and use them as a pin which means the world origin.  Once all of that is done, c4d can solve the camera.  It's all based on a single image, not a video.  I'm just wondering if you can do the same in blender.  Here's a video of it in c4d - https://www.youtube.com/watch?v=CIt6jKXEITc

not using the tracker, but there is a great (free) addon that will help you here (sounds like it works the same as cinema 4d).

@David your recommendation is awesome, this should be an answer. (including the github link https://github.com/stuffmatic/blam )


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How do you take reference photos?
I'm trying to model my face on Blender using this tutorial and it gives links to reference photos.
The thing is, as I mentioned above, I want to try and model my face.
So I've decided to take photos of my face. But it doesn't seem to be working well (not symmetrical enough and stuff), so how exactly should I take my reference photos so that it would work well when I try to model it with the Mirror modifier?
Note: I only have the 'webcam' on my Macbook Pro and the camera on my Hongmi phone and I don't want to spend money on a new camera.

I'm voting to close this question as off-topic because it belongs on the Photography.SE site.

I think you can answer this yourself. If symmetry is your problem then take more symmetrical shot or adjust the picture in photoshop. If quality is bad then get better lighting or better camera. Don't know what answers you expect.

Ideally you'll want to take the picture from far away while zoomed in. This will reduce perspective, making the picture more like the orthographic projection you'll be modeling in

Use your phone camera, and hold it as far away as possible to reduce lens deformation. Hold the camera so the lens is at eye's height, as centered as possible. Cut the photo in two using gimp or other 2D software, and mirror it. Even professional taken photos have some non symmetricsl details.
Also take a shot in profile, at the same distance and height, and adjust to keep as close as possible the proportions between the two shoots.
Use the reference just as it is: a reference not a sharp point-to-point grid.

Things you need:

office chair (or any that rotates)
tripod or another thing to hold your camera/phone
good lighting

Steps:

Setup the tripod with your camera/phone.
Setup timer on camera to take multiple shots or take a video.
Sit straight on the chair and rotate around.
Correct minor deformations/symetrics in photoshop


text:
I started rendering a new animation after completely rendering one before. How do I retrieve that older render?
This has happened multiple times, but I would render an image or animation, but would accidentally re-render the image or animation.
How do I go to the UV image editor and find the older render?

Once you've overwritten the old render, there's not much you can do.. There are some practices you can get into to prevent this from happening though

@gandalf3 is refering to rendering to other slots, I think

Screw my life either which way. Blender crashed on me which crashed my PC and lost all seven hours of the render anyways.

That sucks :/ In future, you can save the animation frames to a different folder on your PC (don't use the C:/tmp default)

I know I was also trying to figure that out too like I rendered it but where do I save it? Do I have to compile the png files together to make the avi? Then it crashed. Sadly.


text:
When I import files they "spawn" too far away from the origin?
When I import a model, they "spawn" a bit too far away from the grid, or basically where every Blender project starts. How do I change it so they can be imported closer?

The position of an object is defined by it's origin point. This might help: http://blender.stackexchange.com/questions/23931/move-imported-model-to-the-center-of-the-scene-via-python?lq=1 or this one: http://blender.stackexchange.com/a/24018/3710  ?

For me, it was an option I needed to check when exporting from Solidworks to the STL format:

You can get to this by selecting "Save As" from the Solidworks menu, changing the file type to STL, and then clicking the [Options] button that appears only after you change the file type to STL.
When you check the "Do not translate STL output to positive space," you can wind up with negative coordinates, but if that's what's required to keep your origin wherever it is in the CAD model then that's fine.

Check your object origin on the object in the source blend file. If it's centered on your object, it should link into your new file at the world origin.


text:
Make object glossy, but not reflect other object's colors?
In Cycles, I would like to make a metal object have a shiny, glossy material. The only thing is, other object's colors reflect off of this metal object.
I would like to make it glossy, but not reflect any other colors.
How do I do this?

what do you want it to reflect ?

Well.. nothing, just light, not colors. Like I want to make it have those highlights and reflect light so there is a bit of "white reflection" to this black-colored object, but not reflect colors like purple and red, etc.

you can disable other objects from appearing as reflection if they are not needed in other things

How do I do that?

select the object , go to object tab->Ray_Visibility and uncheck Glossy

You can turn off glossy reflection for each of your other objects but that's not very good practise because you may want them to reflect on each other. In blender internal this can be done though. See this answer, it asks the same in a more general sense http://blender.stackexchange.com/questions/983/exclusive-lighting

One way to do this is by preventing other objects from appearing as a reflection on any glossy material by disabling the Glossy option in :  Properties➩Object➩Ray_Visibility


text:
I Used Shift + L to select all objects in common.. how do I apply a material to all of those now?
I did Shift + L to select objects with the same default material, but now how do I apply a material to all of those?
It will only apply a material to the original one I wanted to compare the other objects with.

You select all the objects that you want to apply material to, with the one that you already applied material to as the last selected one, then hit CTRL+L (make links) and choose Materials from drop down list.


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How to make objects independent?
In Cycles, I imported a car, which a bunch of parts (in .obj format) I assembled together.
For some reason, when I apply a shader to one part, it does the same to  a bunch of other objects, like the ones with the same color or property.
Could be because in this editor where I put the vehicle together, all the object's names are the same or something?

To add multiple materials to an object which I believe will help, do the following:

Select different faces.

After preparing your various materials, select a material and press "apply."

Tadaa!

I really hope that helps. :)

That wasn't what I wanted. I have actual objects, not faces, and when I apply a material to ONE, it does it to all the others for some reason. I only want it to apply to one object

That's because all of your objects are sharing the same material. Add a new one on your objects

Binary Green, all the Objects will have faces when you enter Edit Mode:press the Tab key.  Then use Ctrl+Tab->Face to activate Face Select mode.  There is also a button in the header to do this.  Look at the right side of all the images posted.  They have two materials listed, a blue one and a red one.  That is how you control what materials are attached to the various parts.  They are not assigned per object, they assigned per face.  This was done automatically for you upon import but now it's up to you to re-define them manually.


text:
How to make hair material different from the plane itself?
In Cycles Render, I added hair to a plane (as I was making a grass field) and I don't seem to know how to make the actual flat plane's material different from the hairs themselves, because I'd like to make the plane have an image texture and the hairs have a yellow-like color to them, but of course, if I attempt to make the material yellow-ish, the plane AND the hairs will become yellow. I'm done with the plane, I just want to control the hairs' materials.

Related - https://blender.stackexchange.com/questions/31778/i-cant-get-the-hair-on-my-model-to-render-or-even-apply-color-buzzcut/31784#31784

You can change the strand's material by adding another material slot in the materials pane, then go to particle settings panel > render rollout and select the new material in the material slot dropdown list.
Add a new material slot:

And select it in the particle settings:


text:
IK with pole over subdivided bone chain don't bend
Adding IK constraint with target and pole over subdivided bone chain don't bend
Steps:

Add single bone
Subdivide(W) in two
Extrude from final tail the target and clear parent
Add new pole bone in front of first joint
Add IK constraint with target. With this configuration the ik works well
When pole bone is added in IK constraint the joint don't bend

The bones transformations arent blocked in bone panel. The same configuration with extruded bones work well. Where is the blocking configuration option?
Blend file

Yep. This is a bug with the Armature system and may be worth reporting. I think the issue is that it doesn't know which side of the bone is supposed to face the pole target.
However, if you rotate the IK bone after moving the target bone, the IK bone will snap to position, and work.
Rotate

Snap

Thank you @CharlesL this way fix the constraint. The bug is reported and confirmed by developers


text:
Which engine in Blender should i start with?
I just started learning Blender and I noticed that there are two engines "Blender render" and "cycles render". I'd like to know what is the difference between them in term of Tools, interface (not really rendering time)? I wonder can i first learn Blender Rendering and then switch to Cycles render and use it as easy as trained Blender render? If they do differ so much, please list main advantages and disadvantages. Thanks.

Go for cycles unless you have a really really bad computer. Cycles is far superior, and does many important things by default that are quite complex to do in the internal render engine. Furthermore, hardly anyone makes tutorials about using the internal render engine since it is so in superior.

I got it, thanks. So I shouldn't go with this book http://www.cdschools.org/cms/lib04/PA09000075/Centricity/Domain/81/BlenderBasics_4thEdition2011.pdf it has nothing about Cycles Render? And, yes my PC hardware is ok.

@AitbekMyrzakhmet that is a good starting guide for blender. I would not base my choice of render engine solely off of that book. I'm writing a answer now.

@David I don't see where, other than speed, internal comes close to cycles.

@RayMairlot thank you for that link. I was writing many of the same things.

You can still use that book, but learn cycles as well. BlenderGuru has plenty of cycles render tutorials.

Basically, if you want photorealism, go for cycles.  A lot of people find the material nodes system in cycles difficult to learn and use BI (blender internal) instead, but when you get used to it, it is much more flexible and powerful.  To be fair, there are a few things BI is more suited for, mostly non-photorealistic stuff.  The question that Ray Mairlot linked does a good job of explaining the technical differences.

@PGmath Nodes are harder to learn, but they also force one to think about the properties. When I worked in internal, I always used to use a diffuse shader and mess with the specularity a bit... Now I really study materials...

@GiantCowFilms I totally agree, I am a huge fan of nodes.  Cycles's node system is the main reason I switched from Mental Ray.

As newbies we started with cycles(side note, we still are newbies).  Cycles looks incredible. It seems to be the most common for achieving photo realistic renders in blender. The draw back is that, it is a little slower. And if set for shorter render times, it can introduce noise. The blender internal render engine is a fast and solid render engine. It can take a little more tweaking to get photorealistic results. In some cases photorealistic results can not be achieved. It has some features that have yet to be ported to cycles or in some cases are just now being imported to cycles, i.e. freestyle, halo and volumetric lighting. The blender can be much faster choice for animations as far as render time. We chose to focus on cycles first and work with the internal render engine as needed.  We have been happy with our choice and results. If you need features from one engine that are missing in the other blender has a compositor at its disposal for combining images. We still have so much to learn. We will be looking into other render engines as well.
Summary:
Cycles Pros

Easier to achieve very photorealistic results

Cycles Cons

Much slower than the internal engine
Can introduce noise as artifacts

Blender Internal Pros

Much faster than cycles
Has some features that are not present or not as mature in cycles.

Blender Internal Cons

Not as easy to achieve photorealistic results.

I don't know about halos, but both volumetrics and freestyle have been implemented and are (mostly) fully functional in cycles.

Thank you for that PGmath... We should have been more clear with our sentence.  "It has some features that have yet to be ported to cycles or in some cases are just now being imported to cycles" and "Has some features that are not present or not as mature in cycles."  You are correct with better wording. ;)


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How to align imported mesh to grid?
I've imported a mesh to blender and it's not aligned to the world so to speak and I need the symmetry. How do I get rid of that rotation?.

You can hit CTRL+ALT+Q to toggle quad view mode, showing your model along all major axes.
From there, you can rotate with r for manual corrections. For finer control, hold Shift while you rotate.
Edit: An alternative method to ensure a symmetric mesh when you're done:

1 to view from front
Tab to enter edit mode
z to display wireframe
b+box select the whole left side of your mesh (you may need to Ctrl+r add an edge loop down the mid-line first)
x delete selected vertices
Add and apply a mirror modifier along the x axis

Not sure how this will differ from what you described in your comment, but it's an option

Ok, thanks. I need perfect match for later work in zbrush so I ended up using manual adjustments and then mesh>symmetrize

You can do this with Mesh Align Plus (my addon). After installing the addon, either watch the steps in the GIF or read the text version below:

The feature you're looking for is the Quick Align Planes operator in the 3D View > Tools Panel (T) > Mesh Align Plus Tab, in its own panel.
1. Pick a destination target (stationary plane that you're aligning to)

In edit mode (Tab), shift + right click to select the three verts you want to align your object with (a rotated plane primitive can be used here)
Hit Grab Destination

2. Pick a source target (plane that will be aligned with the destination)

In edit mode (Tab), shift + right click to select the three verts that need to line up with the destination when the alignment is applied. Leave them selected.

3. Apply the operation

Click the checkbox for Enable Experimental Mesh Operations (your object cannot have non-uniform scaling applied, so this is to warn you of that).
Make sure the object you want to move is selected, and (in object mode or edit mode) hit Apply to: Whole Mesh


text:
Mix node to limit value
Can anyone figure out why a mix node with black and white was used in conjunction with the minimum and maximum nodes of this node group? The purpose of the two math nodes (with minimum and maximum) is to limit the input value (in the upper input of the Mininum node) to a smaller range.
Currently the maximum and minimum are set by changing the Fac(tor) input of the mix nodes. However, in my head the result should be the same if I simply control the value by the lower input of the math node?

OK, after some more experimentation, the only explanation I can find is that the author of the node group wished the input to be a slider instead of simply a value. Perhaps this makes sense, since the values should be between zero to one.
Does anyone else find some other explanation?

It seems like that's their way of fashioning a handle for the node group.


text:
Packing multiple objects for 3D Printing
I am looking for an addon/script that packs multiple objects together to take as little scene space as possible, this is for 3D Printing services that charge per bounding box of all objects in a file (objects arranged as neatly as possible without too much empty space in between).
The feature is present in an expensive 3D Printing software called Magics.

I think there's not (yet) such addon, the only 3d printing related one (included by not enabled by default) has not this feature, but I guess it also depends on some printer spec, like the printing area shape, maybe other things, like the printer type (a powder sintering printer can print things in a very different way than a fdm printer, eg).
The only thing you can do now in Blender, if it helps you, is to use the UV map "pack island" tool to simulate the best layout from the objects you have in the scene, maybe.
If you can find out what is the shape for each object that has to fit (it could depend a alot on the objects shapes), you can create a plane for each object shaped like its limits.
Then merge those separate planes together, in a single object and then UV unwrap them. The UV/image has a "pack islands" that can optimize the UV maps on the texture space.
Here I did it with some basic shapes, just to get you the idea:

I just used the largest horizontal face for each separate mesh. I know it could not be realistic, is just to give you the idea.
If you can consider the texture space as your printer printing bed (ie: only square print beds), the UV can be optimized to fill it (you can also scale them).
then the "pack islands" could help you to find the best way to pack them in that space. eg going from

to

then, of course you have to replicate that layout in the 3d view to get the same suggested placement. If this helps you you can also export the uw layout as .svg and then import tht svg into blender, to help you as a reference (eg: snapping)

This is essentially 2D packing what you presented, quite useful indeed. Unfortunately not in my case. My model is a large scale model of a property, to be printed on an SLS machine, I had to split it into parts so it fits on the printer's bed. I've worked on a couple projects like this one and packing objects is always quite tedious but necessary to save money (the service i use charges per bounding box, all 36 of my objects are packed in one STL). some of the objects are L shaped or at an angle so the 2d technique doesn't quite work with them.

I suspected that... is it this kind of thing https://en.wikipedia.org/wiki/Bin_packing_problem ? If yes, it seems to be a NP-complex class of problem...

but probably more complex, as shape has to be taken into account, like http://cimar.mae.ufl.edu/CIMAR/pages/thesis/Pasha_A_CISE.pdf or http://www.researchgate.net/publication/222533158_A_packing_algorithm_for_particles_of_arbitrary_shapes


text:
Blender 3D 2.78b on OS X El Capitan 10.11.6 - CUDA error at cuCtxCreate:
I am experiencing CUDA crashes on Blender 2.78b.
The error given is the following:

CUDA error at cuCtxCreate: Launch failed.

It only happens with 2.78b, I've tried both 2.78 and 2.78a and there CUDA works correctly.
I am using clean versions, without changing any settings/installed addons.
The scene consists of the default cube, a single light and a camera and the Feature Set is set to 'Supported'.
The graphics card I am using is - NVidia GeForce GTX 780M 4096 MB, I also have the latest CUDA version installed, see screenshot below.

More info regarding the system, see below.

Has anyone experienced CUDA issues with Blender 2.78b? I noticed that this version moved to CUDA 8.0, which I am now using.

Had this problem earlier today.. just had to restart my computer. I'm sure you've already tried that buy you never know

I did so indeed.. :(


text:
Texture painting without rendering vertex paint
I need to apply a texture paint to a mesh that already has vertex colors attached to it:

When I want to draw on this mesh in texture paint mode the vertex colors get applied too:

As you can see, the vertex colors make it hard to see anything of the texture paint in the dark areas.
How do I disable the vertex colors during texture painting?
As a less important side question: How do I disable lighting as well?
I just want the pure texture to be displayed during painting.

You can enable Shadeless in your material to remove the shading.

Switch to GLSL shading and enable Shadeless in your material settings:

With GLSL enabled in texture paint mode, wireframe view will display only the vertex colors, solid will display both, and textured will display only the textures.


text:
Transform Effects Strip Real Values
I am using the video editing function of Blender to make a image pan & zoom clip (aka Ken Burns). The image is a chart I made in Photoshop and I want to zoom into an exact point on the chart and a exact zoom level.
In the effects strip controls, there are places to adjust the scale as well as the position, but I can't figure out how the values in these boxes translate to real-world values (in my case I want to go to exactly 300%, centered on the 508x291 pixel spot on the image).

This could be a solution with VSE, but you'll get a blurried image (if you scale 300%)
Some consideration first:
The effect strip will scale always from the center of the image.
If you want to scale from the point A (508x291px from the top-left corner), you have to move the point A to the center first, then scale.
Pan and zoom in VSE

Add the first effect stript to translate the image by the offset you need.
Add the second effet strip to scale (3 = 300%)

Some math:
If your image dimensions are 1920x1080px:
first effect strip (position)
center: xc=960, yc=540
pointA: xa=508, ya=291
translation: xc-xa, yc-ya = 960-508, 540-291 = 452, 249

second effect strip (scale)
scale 3 = 300%
As you can see, the quality of the image is very low.
Since you are scaling 3 times the size, the resolution is 3 times lower.

Note
When you deal with scale in VSE, you have to pay attention to the original size and the render size.
When you add an image (or a movie clip) in the video sequencer editor, the image will be scaled to the render size.
If you want the image to maintain the original size, you have to check the "Image offset" option (transform in pixel).

Doing so, you can pan the image and center the point of interest but you cannot scale it down, because the image will be cropped.
If you want to zoom an image, I suggest you to use the node compositor or a camera moving in front of an image plane in 3d View.
Pan and zoom in 3D View
Using the 3d View, the image texture can be bigger than the render size.

Activate the "import images as planes" add-on, if it is not yet activated

Import the image to stage

Some considerations about the options:

Check "Shadeless"
If you're importing image with alpha channel (png), check "Use Alpha" and "Z Transparency"
If you want the image to have precise dimensions, the best choice is "Plane dimensions: Dots/BU)": it allows you to determine the dimensions starting from the pixel size (eg: 1920 x 1080px at 100 Dots/BU -> plane dimensions: 1.920 x 1.080 BU)

Pan and zoom in Node Compositor
Here a possible node compositing:

Thanks for these hints. I added another "Scene" that only does the animated image transform with the Node Editor as suggested and was able to use this in the original Scene in the Video Sequence Editor (VSE) instead of an effect strip.

In the sidebar for the Transform Effects strip you'll see 2 fields for Scale X and Y. The default value is 1.0 which equates to 100% scale of the clip to be transformed. Animating the XY scale values up to 3.0 should give you the 300% scale effect.
For the position values, the XY values are also percentage, but this time 50 = 50% and 100=100%. To animate the position to the exact spot on the screen, I think you'll have to use the trial and error method and eyeball it to get something that works how you want.

The transform effect strip is what you will be using. Just understand that it has several different operating modes depending on whether you choose Translation = Percent or Pixels, and do you check the Image Offset box?


text:
Render over the previous render result
Is there any way to get Blender to paint a fresh render over the top of the previous render, to make it easier to see the result of changes?
So: I render a scene, then make some changes, then hit render again, and instead of being blank, it shows the previous render result, but gradually replaces it with the new result.

One alternative is to switch to another render slot prior to rendering ("slot" dropdown in the header of the image editor, or by pressing the number keys in the image editor). This way you can rapidly switch between different slots to compare renders, even after the renders have completed.

You could technically do this in the compositor, but you would have to make sure to save each of your renders out as images, and then be diligent to add them all back into the node editor. Then you could use (overlay, add, multiply, Mix, etc...) nodes to see the backdrop change.
It may be a very good way to learn the "Gut Feel" of what your parameters are truly affecting.

Not what I'm after, but good to know.


text:
In 2.8 how can I return the 3D cursor settings back into the Item tab?
Prior to 2.8, the context menu (N) showed both the current selection properties and the 3D cursor properties, which I found very useful. Now I have to constantly mouse up and switch the tabs, and it's frustrating me.
It doesn't seem like I can drag it to the Item tab. Is there any way to return to the old layout, just for this feature?

bl_info = {
    "name": "Additional 3d Cursor Panel",
    "author": "Martynas Žiemys",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "location": "n panel, Item tab",
    "description": "Adds 3d Cursor properties to Item tab",
    "warning": "",
    "wiki_url": "",
    "category": "UI",
}

import bpy

from bpy.types import Panel

class VIEW3D_PT_view3d_additional_cursor(Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "Item"
    bl_label = "3D Cursor"

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

        cursor = context.scene.cursor

        layout.column().prop(cursor, "location", text="Location")
        rotation_mode = cursor.rotation_mode
        if rotation_mode == 'QUATERNION':
            layout.column().prop(cursor, "rotation_quaternion", text="Rotation")
        elif rotation_mode == 'AXIS_ANGLE':
            layout.column().prop(cursor, "rotation_axis_angle", text="Rotation")
        else:
            layout.column().prop(cursor, "rotation_euler", text="Rotation")
        layout.prop(cursor, "rotation_mode", text="")

def register():
    bpy.utils.register_class(VIEW3D_PT_view3d_additional_cursor)

def unregister():
    bpy.utils.unregister_class(VIEW3D_PT_view3d_additional_cursor)

if __name__ == "__main__":
    register()

If you copy and paste that into the Text editor and then save it to a file with a .py extension, you can then install this as an add-on, that adds the functionality:

I'll try this. So if future UI changes make it so that this start throwing errors, would I be able to disable this "addon" like any other?

Sure, it's formed as any other add-on. It is a simple add-on.

Makes sense. Thank you for knocking this out. I am having trouble finding it after installing though. Searching for the name (or partially) doesn't show any results, and it doesn't appear to be working in the interface. There was a little blurb about one or more addons not being UTF-8. I made sure the file I created was UTF-8 encoded, so not sure what could be wrong.

Nevermind! I didn't save the encoding change lol. Works like a charm now.

That's why I meant to recommend to copy it to Blender's Text editor - it saves as UTF-8 by default as far as I know. Anyway, glad it works now.

Sticking to a standard Z over Ž will alleviate that happening.

I like my surname as it is. Luckily, UTF-8 encoding is perfectly suitable to encode it without mistakes and as far as I know, Blender uses UTF-8 for pretty much everything. I am even able to enjoy variable names containing all of my favourite letters such as ą, č, ę, ė, į, š, ų, ū and ž in my scripts. :)


text:
Assign an object to 2 parents with offset for each
I have a game character who uses a shield. Her armature has 2 bones for the shield: the "stowed" position and the "using" position - i.e.: the shield is stowed on an extended back bone, and is used on an extended hand bone.
I can parent the shield to both bones by using the ChildOf constraint, but it only gives the ability to use the parent's position verbatim. I need to position it at the parent, but with an offset. Like, hand bone but rotated on X by 30, and back bone but rotated X by 15.
Is there any way to do this? Something like a ChildOf-plus-Offset?

I've figured this out.
I created an Empty for each target bone, parented each empty to the respective bone, positioned it as desired, then used the empties as targets for the ChildOf constraints.


text:
Prevent splash screen from being shown when using a script?
I'm writing a Python script that creates a Blender scene; I'm running it from the command line with blender -P script.py. However, the splash screen always appears and it's really annoying. Is there something I can do from the script that prevents the splash screen from showing up for just that invocation of Blender? Note that I do not want to change the global preference.
The tooltip over the user preferences splash screen setting recommends bpy.types.UserPreferencesView.show_splash, but changing this from my script doesn't seem to do anything.

Is there a reason why you invoke your script via command line in window-mode? You would typically run a script via a button in the UI if you work in Blender, or run a script via command line with blender in background mode (no window, usually for rendering).

I'm not working in Blender. I'm just using it to look at the results of another tool.

The attribute to change is not in UserPreferencesView type, but in that class' instance. The right instance to modify, currently used viewing data preferences, is the view attribute of bpy.context.user_preferences:
import bpy

bpy.context.user_preferences.view.show_splash = False

2.8: bpy.context.preferences.view.show_splash = False

The previous answer was correct before, but now the interface has changed.
After Blender 2.80
import bpy

bpy.context.preferences.view.show_splash = False

Before Blender 2.80
import bpy

bpy.context.user_preferences.view.show_splash = False


text:
Mangled physics after moving an object
I'm trying to do some simple 2D physics. Here's a working version of the animation (I told you it was simple):
https://imgur.com/a/vWdC54K
I now move the rotating green element a bit to the right; I delete the bake; rebake; render.
https://imgur.com/a/gReFX2Y
It's very wrong. (I don't know how to get the movies inlined, sorry. If any helpful editor knows how, feel free to fix...)
This doesn't just happen when rendering, it also happens when doing normal un-baked editing. In fact, it seems to be completely independent of the bake state. What's really weird is if I add or remove a ball, everything resets and it's working again.
This sounds as if the physics cache is stale, but in the second video the balls are moving differently to the first, so there's something more going on than just using the old position data for the balls. I have seen references that editing the scene causes the physics cache to be flushed, which explains why everything fixes itself when I add or remove a ball, but surely moving the rotating bar should do the same?
Is there any way to avoid this? Even a way to manually flush the cache (if that's what's needed) would be nice...
(The red balls are rigid body active objects. The green frame is a passive object. The rotating bar is a passive object with animation enabled and a driver on the rotation Y property to make it move. The green way have 1u of depth perpendicular to the camera and the balls themselves are discs with a spherical collider.)

The first thing I notice is that in the first animation the red balls are touching or at least get very close to the rotating green bar, while in the second animation they are repelled when they are still quite far... did you change the Collision Margin under Collisions > Sensitivity? Or maybe you changed the Shape to Mesh or something like that, in this case the Collision Margin checkbox automatically disappears and you just have a Margin value which is 0.04 by default....

I did check that, and no. It goes from not working to working if I simply select one ball, to Shift+D to duplicate it, place it somewhere, and rerun the animation. I never touch the collision margin setting.


text:
How to combine 2D animation and motion tracking?
I'm trying to do a 2D animation. I'm compositing a shape on top of existing video footage, and I want a figure to follow the motion of someone in the footage.
Because this is all 2D, I don't want a 3D solve --- ideally I want to be able to create tracks in VFX->Motion Tracking and then make my figure's bones' screen coordinates directly match the position of the tracks.
I haven't been able to figure out how to do this. Most references online are either dealing with full-on 3D camera solving, or with 2D rotoscoping. One of the latter says I can reparent rotoscoping points to the track, which is precisely what I'm looking for; but I don't seem to be able to reparent renderable objects to tracks, and besides, wouldn't reparenting a bone interfere with the way it distorts the figure?
I'm sure Blender can do this, because it can do anything. But how?

Start with a VFX type project in blender.
Do the motion tracking in a regular way.
Once you are happy with it, You assign it to an empty (Reconstruction -> Link Empty to Track).
Then you add a 2d Animation Tab to you project and in the constraints you copy transform from the empty to your grease pencil object.

Perfect! Thanks! (I wish Blender functionality was more discoverable...) I'm actually using the 3D modeller, but in 2D, but the empty appears in the modeller and is locked to the current camera's screen coordinates. This is precisely what I want. If you copy that to an answer I can mark it correct!


text:
How to force bones to follow tracking points?
I'm trying to animate a 2D figure. My figure is a flat subdivided mesh with an image on it. There's an armature representing the figure, and I have a set of tracking points linked to empties in the model which indicate how the figure is supposed to move. (Knee, foot, hand, elbow etc.)
What I want is for each bone to precisely follow its particular tracking point, stretching as necessary. However, I can't seem to make this happen. I've tried the Inverse Kinematic bone constraint, but even with the bones set to maximum stretchiness this is refusing to stretch the bones far enough to reach the tracking points, leading to garbage results and flailing as the solver tries to find a solution.
I've tried Stretch To, but this doesn't work either --- I suspect it does something else entirely. There are no other suitable constraints (and I've tried a number of unsuitable ones).
Is there a way to do what I want with armatures, and if so, how? Or, given that bones appear to be intended to be stiff rather than stretchy, am I using the wrong tool for the job, and if so, what tool should I be using?

Stretch-to is the answer.  If that's not working for you, we need to see the file to be able to figure out why.

After doing some tinkering, yes, stretch-to does work --- but it doesn't work the way I expected. Instead of stretching the bone so that the end coincides with the object being tracked, it applies some kind of multiplication factor based on the 'original length' property of the bone, which is always wrong. So, I have to add the stretch-to constraint and then manually adjust 'original length' until the end of the bone is on top of the tracking point. It then works the way I expect. I'm sure there are reasons for this, but I don't know what they are.

It stretches according to the rest length given; the default rest length given is calculated from the current distance.  If you want to know the exact rest length there are a number of things you can do, but usually, it's simplest just to alt g alt r alt s reset the pose so that the stretch to marker is exactly at the tail of the bone (since you put it there in edit mode, right?) then click the X button next to the rest length.


text:
(VSE) How do I speed up audio by more than 10 times?
I'm trying to speed up some video by a factor of 20, audio included. The video strip is easy: I just add a speed control transform strip. The audio part isn't as easy. Transform strips don't work on sound strips, so normally I use the Pitch Control feature on the audio strip. Unfortunately, it looks like there's a hard-coded limit of 10 on this:
  prop = RNA_def_property(srna, "pitch", PROP_FLOAT, PROP_NONE);
  RNA_def_property_float_sdna(prop, NULL, "pitch");
  RNA_def_property_range(prop, 0.1f, 10.0f);
  RNA_def_property_ui_text(prop, "Pitch", "Playback pitch of the sound");

Can this limit be overridden somehow (without recompiling Blender)? Is there any other way of changing the audio speed more than a factor of 10?

I'm not sure how to do it in Blender, but you could always speed up the audio in another program such as Audacity (which is free and open source).  In Audacity, you just have to drag and drop the audio file into the program, drag to select the entire audio strip, and go into Effects -> Change Speed.  Then you can go into File -> Export to save it and then import it back into Blender.

Yeah, but as I'm dealing with the audio track which is part of a video clip which has already been cut in the VSE, that would end up being a synchronisation nightmare, so I very much want a pure Blender solution.

I don't use VSE, but hardcoded limit of just 10 is a really odd choice... Perhaps ask the devs.

@DavidGiven Maybe you should leave a note on the subject here: https://blender.chat/channel/vse
(If the link doesn't work in your browser, then try https://blender.chat/ click the globus icon and find the vse channel that way)
Sounds like a quick fix patch.


text:
Pointing the camera in a particular direction programmatically
I'm trying to use Python to place a camera. I know the camera's location, and the forward and up vectors for the camera (i.e. the direction it's pointing and its orientation). How do I do this?
I know that it's possible to calculate a raw world matrix from the above information, which I can then apply to the camera, but I was rather hoping not to have to. Is there an easier way?

do you want to set the cameras direction in the game engine?

No, I'm writing a script to create a scene with the camera in a specific location.

Heres a script to make a camera point towards any point in space.
import bpy

def look_at(obj_camera, point):
    loc_camera = obj_camera.matrix_world.to_translation()

    direction = point - loc_camera
    # point the cameras '-Z' and use its 'Y' as up
    rot_quat = direction.to_track_quat('-Z', 'Y')

    # assume we're using euler rotation
    obj_camera.rotation_euler = rot_quat.to_euler()

# Test
obj_camera = bpy.data.objects["Camera"]
obj_other = bpy.data.objects["Cube"]

obj_camera.location = (5.0, 2.0, 3.0)
look_at(obj_camera, obj_other.matrix_world.to_translation())

I'm afraid I don't understand this --- the docs for to_track_quat() are... brief. I don't see how the fixed axis parameters get rotated to point in my desired direction. (When I say I have the location and forward and up vectors, I mean literally I have a Point and two Vector objects.) Can you expand?

The camera starts off pointing along the -Z axis with the top of the camera pointing along the +Y axis. The variable "direction" is the vector from the camera to the point. The function direction.to_track_quat('-Z', 'Y') returns the quaternion that rotates '-Z' so that it aligns with the direction vector. This rotation is not unique because the rotated camera can still rotate about direction vector. Specifying Y gives the rotation quaternion with the -Z vector aligned with the direction vector and the Y vector pointing up.

You might want to call bpy.context.scene.update() after changing the camera's location to make sure the matrix is up to date.

+1 for @Daerst 's suggestion to update the scene, this fixed things for me. However, in Blender 2.8+ you'll need bpy.context.view_layer.update() instead.

Here is a version of ideasman42's look_at function
that also allows you to roll the camera (or any object) about the axis from camera to target:
def point_at(obj, target, roll=0):
    """
    Rotate obj to look at target

    :arg obj: the object to be rotated. Usually the camera
    :arg target: the location (3-tuple or Vector) to be looked at
    :arg roll: The angle of rotation about the axis from obj to target in radians.

    Based on: https://blender.stackexchange.com/a/5220/12947 (ideasman42)
    """
    if not isinstance(target, mathutils.Vector):
        target = mathutils.Vector(target)
    loc = obj.location
    # direction points from the object to the target
    direction = target - loc
    tracker, rotator = (('-Z', 'Y'),'Z') if obj.type=='CAMERA' else (('X', 'Z'),'Y') #because new cameras points down(-Z), usually meshes point (-Y)
    quat = direction.to_track_quat(*tracker)

    # /usr/share/blender/scripts/addons/add_advanced_objects_menu/arrange_on_curve.py
    quat = quat.to_matrix().to_4x4()
    rollMatrix = mathutils.Matrix.Rotation(roll, 4, rotator)

    # remember the current location, since assigning to obj.matrix_world changes it
    loc = loc.to_tuple()
    #obj.matrix_world = quat * rollMatrix
    # in blender 2.8 and above @ is used to multiply matrices
    # using * still works but results in unexpected behaviour!
    obj.matrix_world = quat @ rollMatrix
    obj.location = loc

It can be used like this:
import math
cube = bpy.data.objects["Cube"]
cube.location = (5, -5, 5)
cam = bpy.data.objects["Camera"]
cam.location = (5, -5, -2)
point_at(cam, cube.location, roll=math.radians(45))

One way is to assign tuples directly to the camera object's location and rotation_euler attributes. For example, with the camera selected:
import bpy
from math import radians

camera = bpy.context.object
camera.location = (1.0, 0.0, 1.0)
camera.rotation_euler = (radians(45), 0.0, radians(30))


text:
Creating custom or repeated transition effects in the VSE
Let's say I want to create a video with a large number of fairly complex transitions --- for the sake of argument, let's consider an old-fashioned carousel project slideshow. On each transition, the image needs to be moved off to the left, with the new image moved on from the right.
Setting this up once isn't too bad; I spend a few minutes fiddling with the keyframes and curves, and it's done. But now I have 150 more images to apply the same effect to. What's worse, once I render and send it off to my boss they're likely to send it back to me telling me to speed up every transition by 5%.
What I'd really like to do is to create a custom effect strip which applies the effect; then whenever I want my effect I simply overlap two images and apply the custom transition. Crucially, I would then be able to edit the transition strip to change the timings throughout the video.
Is such a thing possible, and if so, how?
Things I've looked at:

I've looked at metastrips, but I don't think they're usable as effects. Plus, I don't think I can create a linked duplicate (Alt+D doesn't appear to work in the VSE), so I'd still need to go through and edit each one manually to adjust the timings.
I know about mask effects, which look great, but they can only overlay one strip on another, and can't apply effects like translations or scales.


text:
Where is the implementation of the Cycles image-nodes sampling?
Where is(are) the function(s) that, in the image node, transforms a point in UV space (vector that goes into the node) to a color (color of the pixel of the texture)? I can't seem to find such. Thank you very much in advance.

do you mean the texture coordinate Input --> texture coordinate? and mapping node Vector --> mapping?

No, I mean the Image Texture node. ("ShaderNodeTexImage", if I remember right.)

Texture>Image Texture

UV coordinate is a X/Y coordinate for an image. There is no transformation.

Sorry if I'm unclear. Let me rephrase: I am talking about the code that takes in the vector / UV point / whatever one wants to call it and returns the color of the pixel at that place.

What you are looking for is in
\scripts\addons\cycles\shader\

You want to look into:
node_texture_coordinate.oso
node_image_texture.oso

You will find there links to appropriate .osl or .h files.
In those you will find the code and implementation.

Texture > Image Texture, then connect it to the Diffuse Shader


text:
Using mathutils outside of Blender
I have installed mathutils 2.81.2 in my Python 3.8.5 install to use outside of Blender. However, nothing seems to work. E.g. I cannot create a unit matrix m = mathutils.Matrix() and find its components by subscripting it m[0][0]. I get TypeError: 'Matrix' object is not subscriptable.
Printing it simply returns the default <mathutils.Matrix object at ...>.
And trying to multiply two matrices using @ or a matrix with a vector gives a TypeError: unsupported operand type(s) for @: 'Matrix' and 'Matrix'.
Isn't mathutils supposed to work outside of Blender? After all, I can install it fine using pip.
By the way, I have also tried the same on Python 3.7.4 (which was the version used in Blender 2.81). I get the same problems there.

It is working for me. I think you have problem with installation.

OK! Thank you! That was indeed the case! Reinstalling python completely solved my problems!

Actually, reinstalling everything, it turns out that there was an incompatibility problem. The fake-bpy-module (which is used to get syntax autocomplete outside of Blender, apparently overrides import mathutils and instead just imports a fake version that does nothing.


text:
Exporting cycles rendered models to be used in opengl

The cube in top left corner is the default cube with change in view port color. I added checker texture to it using nodes and got it rendered using cycles render. When I exported them to be used via opengl API, the cube in top left corner,i.e. without texture, gets displayed.For any model, the only effect I observed is the change in viewport color in the model, which gets displayed via opengl. Is there a way to use rendered model or models with texture and other details added to it?
P.S I have Open Asset Import Library to load scene and GLSL for implementing shader source.

Do you want to bake the light and materials to a texture you can use with OpenGL? There are multiple tutorials on Cycles baking, including this one by Blender Guru. Have a look, it might help you.

Seems you need baking. https://www.blender.org/manual/render/workflows/bake.html Carsten

Even after baking the textures, it's likely that the exporter will not recognize the textures since exporters tend to be written to work with the Blender Render(Internal) material system.  To export, you pretty much have to make a copy of the .blend and delete every material from Cycles then re-add materials using Blender Render for the exporter to function conrrectly.  Simply disabling the Cycles nodes may not be enough since the exporter may detect them and then fail the way the SketchFab uploader does.

I used the cycles baking and got a textured mesh in Material Viewport Shading, yet I cant get it to load completely,i.e. with texture, when I export it as collada file, .ply or .obj type files. To be precise I need it for game development but cant seem export model along with textures.

The main problem is that baking with Cycles is still fairly new, less than one year at the time of writing.  Blender's various exporters were designed before this and they are built upon the older Blender Render(Internal) Material system.  Here is a print-screen of the main Blender Render Material System.  Although BI has nodes as well, I'm not so sure they will work well with exporting either.

So let's go back to Cycles for a moment.  Here is a setup that has a texture which was baked using Cycles bake.  The baked texture is chosen by a node as seen in the node editor but the current problem is that this node will not be recognized by the various exporters as being a texture that should be exported along with the model.

Here is an example of one difficulty that can make upgrading the various exporters to work with Cycles a bit complicated.  There are three textures in the following node setup.  One bake-to texture, one texture for the diffuse color input and one normal map.

Now it could be decided that the texture which is not attached to anything should be the texture to be exported as the main color texture, however, Cycles nodes allow for more than one node group as shown in the following image.  The setup shown would make consistent and reliable exporting very difficult but it makes the Cycles material system very flexible.  These two ideas conflict.  It's not at all clear for this situation which baked texture(s) should be exported.

So for now what you can do is switch to Blender Render and deactivate the Nodes as shown in the following image.

Now click the tabbed icon for textures that is to the right of the Material tab icon and add a texture slot.  Next, assign the baked texture to this slot.  (Now you should be able to export without too many problems.)*

*as I mentioned in the comment earlier, leaving the Cycles nodes intact but deactivated can still cause the exporter problems.  For simple scenes it doesn't always happen but with a complex scene that has 100 models and hundreds of textures all linked into the Cycles nodes system, things can get hairy for the exporter.
The textures may be detected but the exporter may not know what they mean and it could fail because of this.
The SketchFab exporter was doing this to me this past spring.  It's probably better to save the .blend and create a duplicate of it and then just delete all the Cycles materials and build them up again using Blender Render(Internal) from the start.
It's a nuisance but until someone with coding skill finds the time to deal with it, this is what we are stuck with. (unless someone knows something I don't and they would like to share.) :)

thx, I think this explains the same btw, I am too new on this anyway, so I am reading both :)

Since other renderers (except maybe Strata 3D) don't have a Cycles renderer or equivalent, it won't make sense to export that way because the other software cannot interpret Cycles proprietary data such as Nodes. The file would have to be exported as only the model itself and the UV map, and specular attributes applied in the receiving software.

authors: Вовочка Викторович


text:
Import key configuration error -- simple problem?
I'm interested in using Blender as a video editing software.
I found a decent tutorial introducing that topic and providing really useful key configuration file, which helps using Blender with a workflow similar to Final Cut Pro.
My problem is -- importing that particular configuration file ends each time with this error:

Here's a transcription of the essentials:
File "...\Blender\2.72\scripts\modules\bpy\utils.py", line 509, in keyconfig_set
    {"_file_":filepath})

File "...\FCP_KeyPreset.py", line 118, in <module>
   kmi.properties.left_right = False

TypeError: bpy_struct: item.attr = val: expected a string enum, not bool

Known facts:

I run Blender 2.72b on Windows 8.1 x64.
My Blender is fresh and clean -- I tried to import my key configuration moments after I installed Blender.
Author of the file is a Mac user and he definitely used older version of Blender, but I don't know which version.

The file can be found here: download link for key configuration file.
It might be worth noticing, that this preset is a part of a video tutorial, which can be found here: Video Editing in Blender - Introduction
halp plox :)

This is a change made in blender 2.72.
The select operator in the sequencer used to use a boolean value (True or False) to select before or after the current frame.
Now in 2.72 it can use 'NONE' 'LEFT' 'RIGHT' or 'MOUSE'. While the boolean values can be entered as True and False the enumerated values need to be in a quoted string.
I believe to get the closest match would be -
Find instances of
kmi.properties.left_right = True

and replace them with
kmi.properties.left_right = 'MOUSE'

and replace
kmi.properties.left_right = False

with
kmi.properties.left_right = 'NONE'

Of course you may want to experiment and adjust it as desired.


text:
How can I get Blender to just do Matcap shading for the selected object?
I have noticed that the behavior of MatCap shading has changed in recent versions of Blender (at least by 2.72b). When I turn Matcap on, all objects are shaded with the same Matcap texture. For sculpting, I only want the selected object shaded with Matcap (as in numerous tutorials).
How can I get it to just do Matcap shading for the selected object (primarily in Sculpt mode)?
Even better would be if we could select a different MatCap material by object or vertex group.

I am afraid you can do it now only in blender internal in GLSL shading. But that shouldn't matter if you want it for sculpting. You only need some matcap textures. Here is what to set:

Good thing is you can setup as many matcaps as you want for your objects:)

Brilliant.  Thanks very much.  After a little searching I found the Blender matcap .jpg files and your setup did the trick.  Now I need to find more matcaps and figure out how to convert ZBrush matcaps for use in Blender (I don't currently own a copy).


text:
Can someone definitively describe the difference between the sculpt flatten, polish, and smooth brushes?
Documentation for the sculpt brushes seems to be a bit spare.  In particular, I'm having trouble properly understanding the difference between flatten, polish, and smooth.
Also, hitting Shift seems to cause one of those to take effect when other brush types are selected.  This is convenient but I'm not sure I'm always getting consistent results.
It would be nice to have all brush types and options properly described somewhere.  I'm starting to learn the code base but I'm not far enough to really tell what the brushes actually do.
Thanks in advance.

Flatten tries to make all vertices align on one plane, smooth tries to align vertices to the average mesh surface, and polish is basically a mixture of the two. This is what I have observed from use and gathered from the Wiki. When pressing Shift while using the Brush tool, you switch from Add to Subtract mode, and the opposite as well.

Flatten tries to make all vertices align on one plane:

Smooth tries to align vertices to the average mesh surface:

Polish is basically a mixture of the two:

This is what I have observed from use and gathered from the Wiki.
When pressing Shift while using the Brush tool, you switch to Smooth mode, and while pressing Ctrl you switch from Add to Subtract mode, and the opposite as well.

Actually, at least on a Mac, it is Ctrl that seems to reverse the sense of Add and Subtract.  Shift seems to switch to smooth but with some of the settings of the current brush.  Thanks!

Interesting! I'm using Windows 7, so it might be different.

@NoviceInDisguise That's peculiar, I use Windows 8.1 pro and used to use 7 HP, and I have always used Ctrl to switch add/subtract.

I updated the answer. I think I might have changed some of my settings, not sure. The default settings act as you said.

Ctrl switches the add / subtract mode to whatever it's not currently set to. If you have subtract selected in the tool shelf, then Ctrl will use add. If you have Add selected in the tool shelf, then Ctrl will use subtract.

That is what I said . . .

This reads like an Abbot and Costello routine.


text:
Adding pole bone to IK ignores IK constraints
I'm trying to rig my character's legs with IK. The way I set it up seems pretty standart, and I see it in many tutorials: I have a foot controller (IK) bone near the foot, which controlls the shin bone with the chain of 2. I have some constraints so that knee doesnt bend sideways, and for the hip joint as well to limit it's movement. When I test it just like that all constraints work like a charm.
However I need some way to control knee orientation, so I add a pole bone to my IK which works out nice, except that the hip constraints are ignored now. Knee constraints still work, but the hip can now bend at any angle imaginable - I can pose character's leg straingt up and so on.
Would really love to hear how I can avoid that problem. Also I'm a programmer, so maybe there's some script or something I should look into, I just dont know where to look because I'm new to blender and modelling in general.

Your problem is limiting Ik bones ranges with constraints. You need to use this panel for Ik:

A simple leg Ik rig is here: How to IK rig legs
How to handle pole bones and their angles precisely is here: How to Set/Calculate pole angle of IK constraint so the chain does not move?

No it's not, because that's the very menu I add constraints with, no? I didn't even know there were other ways. I add constraints here. They work if I just use IK bone. But if I add pole bone as well, then this constraints are ignored.

Well if you add pole bone then these IK limits are ignored, thats correct behavior and only logical.


text:
Why is this mantaflow fireball giving bad quality?
When I render high-res with 450 resolution divisions, the result is completely different from the preview at 64.
I'm using 2000 particles that result in quantized dots of fire, rather than liquid, so I want to blur the particle and have vague swirls of fire like the preview render.
Should I subsample the particle steps or the domain steps?
Why is it so different?
How can I work with previews if the 64 render is completely different to the final render using 450?
hi-res:

low res:

did u bake it both times?

Yes it's properly baked just without noise for the moment I'm going to add the shader controls and see if it helps.


text:
Connecting body parts or clothes problem
I need help guys, I kind of need this for a project or something.
First picture is when I haven't connect everything but when I press " Ctr + J " the result is the next picture. I'm really a noob in blender so what seems to be the problem or are there other ways to connect all the body parts / the clothes?
The problem is the eyes and the goggles.

you have to apply all modifiers (or make sure all objects have the same modifiers) before joining the objects.

One last, PS: In your images you could just crop out the windows UI instead of taking the time to black out the file path.

you could parent them. I would add an empty and place it in the center of the object. Then select all the parts of the object and clothes, select the empty last. Then ctrl + P --> object. If you select the empty and move it, the rest will follow.

Can I ask again another question. If I add an armature in it will it be completely fine? and if I add an armature where should I parent it like the automatic weights.

@kyouma I don't know much about rigging and armatures, so I can't help you with that.

authors: Артур Дедюля


text:
Blender game engine graphics
I know this may be a stupid question but how do I make the background look more realistic or 3d like
here is the game file http://www.pasteall.org/blend/37831

You should pack the textures into the blend file. Right now, none of the textures are available, because they are only on your computer.   2.Could you be more specific about what you are trying to do? You can make the building look more realistic, by:  using a different texture; using more than one background and employing some parallax effect; actually using 3d buildings to create the background plane.   It's a little hard to see what style your going after with the mix of soft, round-character, and hard-edged, pixelated bg art.

How about using 3D objects as background?


text:
How to make an infinite landscape or the floor like in games like temple run in blender game engine?
We have a project in school either we make an animation or game so I decided I would like to make a game like temple run. How do i make the infinite landscape and any suggestion? Thanks :)

You could make several segments that match up to each other, then spawn in these segments randomly as the player progresses

Sorry, I'm not that good at those things. Does that spawning thing need python?

i did something similar in a car game. (Infinite road) If you want to you can download the blend and see how i did it. The file of the Track generator is: TrackGenerator.py
The idea behind the concept is, that you create all kind of objects with the same start and ending. So they have seamless connections. Than you add a new random object when the player gets close enough to the end of your path (or in my case the end of the road).
To controll where to add the next part of the track I created an empty. This empty always is at the end of the path. It is also the object where the script is connected to.
Alway when a new track part is added this empty gets an new Position and orientation. To get this information you need an other empty which is parented to each end of a track part. (those parented objects will automaticly  be added to your scene if you add the track Part, you than can acces them by writing: trackpart.children[0]).
you also need to make shure that the origine of the trackPart objects is at the beginning of the trackPart.
here is an overview what the script does:
it chooses any random trackPart
it adds this part at the and of the Track (with the help of the empty)
than it repositions the empty to the new end of the track.(with the help of the children from the trackPart)
and than it will wait until the player is relativly lose to the end of the track. When he is close enough it will repeat the Process.
here is the code :

from bge import logic as l
from random import randint

def main(co):
    trackGenerator = co.owner
    scene = l.getCurrentScene()
    auto = scene.objects["auto"]
    if trackGenerator["trackLenght"] < auto["distanz"] + 40:
        trackNr = randint(0,anzahlanTracks()-1)
        spawnNext(trackNr, trackGenerator)

def spawnNext(type, trackGenerator):
    scene = l.getCurrentScene()
    name = "TrackPart_" + str(type)
    nextTrackPart = scene.objectsInactive[name]
    next = scene.addObject(nextTrackPart, trackGenerator)
    trackGenerator.worldPosition = next.children[0].worldPosition

    print("size ",next["size"],"   trackLenght: ", trackGenerator["trackLenght"])
    trackGenerator["trackLenght"] = trackGenerator["trackLenght"] + next["size"]

def anzahlanTracks():
    scene = l.getCurrentScene()
    name = "TrackPart"
    anzahl = 0
    for o in scene.objectsInactive:
        #TrackPart_
        if o.name[0:10] == "TrackPart_":
            anzahl += 1
    return anzahl

If you need more information to understand just ask.
CarGame with infinite Road

Link only answers are discouraged as if the link goes down, then so does the answer. Please include some information within the question itself as to how to achieve this.

Guys, thank you for your answer. Maybe I'll try it tomorrow or the other day since I still have some homework to do. BTW thank you very much for responding.

have no time right now so ill will create an description later. but maybe the code in the.blend already helps...


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Why isn't parent offset visible? Any tools to help?
Parent offset in Blender is difficult to understand, because there are obscured values that determine the outcome of user operations. See this question.
Are there any tools/addons to help with this? For example, a replacement parenting/reparenting function, or even a tool to simply display the internal values, to aid in understanding what is going on?
Secondary question, is there a stated or obvious reason for this seemingly intentional operational obfuscation? Is it something worth my time in seeking to drive change or offer to help change?
If you've worked with it for a while, and it now makes perfect sense to you, let me remind you of where others might be coming from. Here's a sample .blend I'm currently looking at:

All of these are simple, visibly identical plain cube meshes with identical rotation, and the object origin at the mesh center of each.
For starters, note that both D and C report translations of 0, 0, 0, and yet are in different locations, both in world space AND relative to their parent. How odd, I think. However, the real confusion is when I try to actually make parenting changes.
We know that there are various operations to unparent, keep transform, clear parent inverse, and set parent. However despite my goal of transferring the child relationship of D from parent A to parent B, nothing results in a destination of H. Various operations result in G, F, and E.
That means that if, historically I've moved something, I might be building objects with defects that cannot be measured through the UI. I had just this scenario recently. Rotations and multiple duplicates were involved, and I had to redo lots of work to get things properly aligned.
For me it was a cautionary tale of "be very paranoid of where things were historically", but that doesn't seem like an ideal lesson for me to learn. Or, maybe I'm just doing something else wrong.


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Can one control a property using real time microphone input
I believe it to be doable, but what would be the most intelligent way? Does using a scripted driver reading from a sound stream make sense? Is there some easier way to do the trick?

Possible duplicate of Controlling drivers with data received via TCP/UDP

Ok, it seems that it can be done with this type of tech.


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Where did the Python UI OpenGL API hide?
Twenty-ish moons ago there was hype about addons being able to do their own OpenGL UIs into panels. This was around the time custom icons became a thing. Now that I happen to need it, I can't find any trace of it. Did I just hallucinate the whole thing? I can find lots of tutorials about OpenGL in the 3D view though.

since blender 2.60 we have the bgl python module. Are you looking for that? https://blender.stackexchange.com/questions/61699/how-to-draw-geometry-in-3d-view-window-with-bgl

Nope. I mean drawing into panels (or nodes to be even more specific) with some sort of custom gl, not into the 3D view. Or is there some way to draw into panels with bgl?