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How to i add a gradient to particles, normal to the emitters surface?
This is a very special question i'd imagine ;)
I have a base shape, that uses a particle system with pyramids on it.

Im triyng to add a gradient to the pyramid-spikes.
This efffect by itself can be easily done in a material for the particle.

BUT: The fade on the pyramids will only be a part of a more complex material for the whole shape.

Currently i convert the particles into a mesh and then join them into one object to achieve this.
I currently have no way to achieve the gradient on each pyramid, but also have control over the material of the whole shape.
So im emulating it with this node setup, someone shared with me.

But this only works partially, since i dont have a sperical shape.
Any ideas on how to solve this problem are well appreciated.
Thanks in advance :)

dynamic paint proximity to the emitter mesh might be worth a try.

What effect are you actually looking for on the whole shape,( ignoring the particles, for a moment,)  that you're only partially achieving with the gradient setup that you show here?

i will add a iridescent effect to the whole thing sort of like this: https://78.media.tumblr.com/02780d0cb02185243e6fe4df2602041f/tumblr_pbikmov0ad1wwb2aso2_r1_400.gif

Gradient texture upon Generate coordinates
To assign a gradient texture to the single particle object you can use the built-in node available for cycles. You can control the gradient with a color ramp node as well.
The tricky part in your setup is that you would like to access the data of a different mesh that doesn't belong to the particle. One possible way is to take advantage of the Object option in the Texture Coordinate node.
You didn't share your setup for the colored shader (the one you show with particles baked and joined), so I'll assume by guessing that you are using the Generate texture coordinate of the object. We can't access that data, but we can try to transform the Object's texture coordinate from an empty object.
In the following example I'm using the Mapping node to translate the empty's (which was created in the same location of the object's origin) coordinates.

An altenative would be to simply move the empty in one of the corner of the object's bounding box and scale it appropriately:

The following image sequence is showing the node in action. The shape on the right is the mesh with particles baked with a shader showing the Generated coordinates to use as reference.

Note: accessing data from other objects may not be possible for all the attributes. Object's texture from another object can only provide location, rotation and scale of the object.

The "from dubli" looks very very promising. i'll try it out and get back with results. Thanks so much already.

It's just a trick that works for this case, don't expect to ba able to do thing much different than what shown. Also it is probably not necessary the "From Dupli" option, you could get the same effect by playing with the vectors... it's just easier to understand in my opinion.

I have no idea what im doing wrong but it wont work. i cant get the from dubli to work. How do you get the particle-material onto the particles ? Cause the material setting in the particle is greyed out as soon as i use objects or a group.  You write that on the left has the particles applied ?

Sorry, I meant "on the right", the one who stays still. I edted the answer. The material is applied to the partcle object that ios being duplicated (the little pyramid on the top in this case, you cen see it also in the image sequence).

ok thanks for clearing that up. But i have no idea how to get the from dubli to work. I even tried a very basic test in a new file. Could you share the blendfile with me ?

Forget the "from duply" option and focus on the external object. I've added a blendfile you can inspect.

This is how it looks for me: https://imgur.com/a/Flkf1Rf i have no idea whats happening

You have to go in Rendered view. Not all the node features are supported in Material view yet .

ohhh god. that has been my problem all along. Thanks again for your patience


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Combine two normal maps and control the strength of each
I use this node setup to combine my two normal maps.

I adapted this method from here.
How to Combine two Normal Maps?
It works perfectly to just combine the maps.
But now i need individual contol over the strength each of them.
Is there a way to do this ?

If you want to adjust each map individually instead of against each other like in the other answer you need to default to straight normal that is (0.5, 0.5, 1). That means with values you need to find difference to 0.5 and multiply it with your weight before adding it back to the 0.5 for each R and G channel.
(the weight field of normal map is placed under the respectful image node)

Another option is to mix the colors, again mixing both with the straight normal color (0.5, 0.5, 1) individually with adjustable factors.

Both methods should do the trick but in the color example the input values' magnitude is halved because of the way the colors are combined.

Thank You :)) This works perfectly when i use the Texture with Non-color-Data

A more precise result can be found using these formulas...
Here's an adaptation of it including a Factor value for mixing:

some more details can be found in this thread in BA
And the nodegroup can be found here.

"More precise" than what?

I' not sure this solves your problem, but do you see that in the Normal Map node on the right of the image there's the strength bar? I would try to use two of them, one for each normal map and then do the whole setup to combine them.
See the image below for reference. Keep in mind that this setup I made is not the correct one, I just made it really quickly as an example of what I was thinking about, you probably need to "combine" it with your solution, just apply a Normal Map node for each normal map you want to control the strength of.

no the two sliders dont help they one change the overall colorshift.

I think this is close to a solution but needs a Normalize node after the Mix to ensure the result is a properly formed normal (with magnitude of 1.0). However, rather than using the Strength to adjust the balance between the normals you should be adjusting the Factor of the Mix node - 0.5 will be an even mix between the two, 0.25 will have the first one 3 times more prevelant than the second one (ie, 0.25 / 0.75 = 1/3... or, more generally, “factor / (1-factor) = proportion of second normal when compared to first).

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Create the circular distorion from an anamorphic lense
I try to recreate the circular distortion of an anamorpic lense
like here

I know about this way to strech the bokeh vertically.
Bokeh - From Horizontal to Vertical
and i have seen this one were a fisheye lense is used.
https://code.blender.org/2014/08/anamorphic-bokeh/
and im using a lens distortion node in the compositor to achive additional realism.
Is there a way to create this circular distortion in the bokeh without a fisheye camera?

This was an inspiring question for me to come across. I spent a darn long time trying these aperture methods without liking the results. This past week i released what i think is your solution, buddy. Four some years later. So sorry i didn't think of this sooner. https://www.blendermarket.com/products/jackimorphic-camera-pack-v1 -jack

You can probably use radial blur to simulate the effect of lens aberration in post-processing.
But the effect is also surprisingly easy to achieve in Cycles with the camera. Just add a black, circular aperture object in front of the camera:

Here is the setup from the camera's perspective. The more closed off the circle is, the heavier the vignetting:

Blend file Download

I dont get this to work somehow. Do you let the camera clip through the object or not ?

Added more detail to the answer, hopefully that answers your question.

Thanks for the Blendfile. It works. :))) But you have to put the aperture really close to the camera

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Volume Scatter Causing More and More Fireflies with More Samples
I am trying to create a cloud of dust, and the volume scatter is creating a large amount of fireflies. However, unlike the other posts I've read, increasing the samples creates more fireflies, and as the accumulate, they create shiny, reflective spots around the edges of my mesh. I have a single spotlight and a blue background to light up the volumetric mesh, and changing lighting features such as "Casts Shadows" and "Multiple Importance" seems to have no effect.
Here's an example of the problem with 50 samples:
one with 200:

and finally one with 500

As you can see the fireflies get more and more concentrated around the edges as the samples go up, and create weird highlights and reflections in the end.
I will note that I am an advanced Blender user, and I am very familiar with eliminating fireflies, but these ones seem to defy logic. I've never seen a problem like this. Any help would be appreciated. Thanks, Graves.

Try increasing and decreasing the size of your spot light, to see its effect.
Consider adding a large plane with emissive light settings and a "go between" opaque plane with a hole in it to substitute for a spot light.
Also consider setting your rendering "clamp indirect" to 0.1 or 0.2 to clean up the fireflies.

I found a work around for the problem, but thanks for your answer!

Please share your solution for the benefit of others that will find this post in their search.

Sorry, I'm kinda new to this forum, I didn't know I should post my solution. Alright

In the Render tab and under Light Paths, try increasing the Max Transparency, or the maximum number of mesh walls that can be transparent before returning any further polygons to a solid color. I do believe this fixes the problem even with an opaque film:

I found a work around for my problem. It appears that when the film is set to transparent this isn't a problem. It still seems like a strange problem, and this solution won't work for everyone, because I'm sure most people use opaque film. But others who stumble upon this problem may want to try this answer!


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How to combine Views of a Multi-View Camera in Composite
I am trying to create a single stereoscopic image in which two camera angles are laid side by side, so that a Google Cardboard lense would converge the two. I have set up two Multi-View Cameras, (one for Left and one for Right), to create the two different views needed. I can use Switch View nodes and translate each of the views to their respective sides of the screen, and should theoretically be able to use Overlay to combine the two as shown below:

However, there seems to be no way to actually combine two views into a single image. If I try to save the resulting composite, it saves it as two files with Left and Right suffixes, but I want blender to do the work and combine the views into one single composite side by side. (I could go into photoshop and change it, but it seems like blender should have this functionality).If I go into the Composite Render Result, the image I get out still depends on the view that I select at the bottom. It appears that there is no Node that combines two views into one in this way.
Here you can see how I get two completely different results by choosing Left:

compared to Right:

even though it seems like the overlay should simply make them one. Also, hooking the Overlay result into both sockets of a Switch View Node does not combine them into one image, either.
I know there are several workarounds, such as setting up Render Layers with two completely different object orientations or two scenes, but I would like to know if there's any way to achieve this simple effect natively. Any help would be appreciated,
Graves Broderick.

You might have the intention of the node confused. The View Switch node is intended to combine two stereo images in compositing, not to split them. In the current Compositing Pipeline (which isn't suited for 3D Compositing) you have to save the images or use renderlayers to make unique changes for the left and the right side.
However you can easily view images side by side and save them.

in the non stereoscopic view mode, you can view the images individually by selecting their channels in the image editor

this button toggles individual image display and stereo image display mode

to view a stereo image side-by-side directly from Blender, make Blender fullscreen AltF11 then choose window > set stereo 3D and choose your desired viewing mode; Blenders whole interface will be side by side

with the "display the image in stereo 3d" toggle button you can switch to individual image display, while in side by side view

in other modes (e.g. anaglyph, interlaced) we don't have to make Blender fullscreen

All these viewing settings don't affect how the two images are handled internally. Once you want to save your image, you have to enter the method (with which the two images are combined) again.
Press F3 in the image editor to open up the save dialog. Under Views Format choose stereo 3d, then select the stereo mode (e.g. side-by-side).
(If your working in side-by-side you have the additional option to squeeze the images horizontally, so that the original render dimension will be respected.)

Wow, that "Side by Side" saving works perfectly! I figured it had to have had a feature to automatically do that for me, but I had no idea where to look before you came along! Thank you for your help!

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


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Unselectable options when creating a new mesh
Good day!
Blender 2.79.
When I create any new object by Shift+A (for instance, torus), I have panel "Add torus" unactivated. Can't click  Generate UV's, Allign to View, Location, etc.
What's wrong?
Thanks for answers.

Global undo needs to be enabled. See this answer


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Exporting a Wet map image in Blender 2.8
Yeah I know how to export a wetmap in Blender 2.79 but I do not find the option in 2.8. I'm talking about the physics tab in Dynamic Paint there used to be an option to save your wetmap. In 2.8 that is just a wird symbol where you can write a title.

With my 2.8 blender built Dynamic Paint only works in the viewport wth the render display mode and the surface canvas. Then I can export it as well and use the resultung images in an image node as a sequence to plug into my material's shader node. It does not work in eevee or in workbench or in the Look Dev mode in Cycles. It really only works in Rendered mode in Cycles with a surface Canvas. Wish I would have gotten that memo. I mean it's supposed to be a major release not a beta. Yeah I'm grumpy about this.


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What kind of topological structures are there?
This is a more open question about the best practices for topology. I couldn't find much about it in tutorials. I want to know what kind of topological patterns are used depending on the object that is being represented. I found this topology online where you have six diamond shaped quads ordered in a hexagon. Are there more patterns like this and what are best practices for topological patterns depending on the material you want to represent?

Consider that topology only matters if you want to deform the mesh.

Your example shows geometry with Subdivision Surface algorithm on top.

Subdivision Surface works with quads, and when they're not there, it transforms the geometry.
Your image shows Subdivison Surface applied on top of triangles.

Further reading (for the sake): https://en.wikipedia.org/wiki/Catmull%E2%80%93Clark_subdivision_surface


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How to properly place Geometry in Geometry Node
I am looking for a way for the cutout object to be displayed on the vertical edges of the cubes in the blend file. I achieved this for now by creating a vertex group and by moving the cutout shape manually until it is more or less at the edges of the cubes.
But I want this to happen in the Geometry Node, so it is easier to control.
I am using the current 2.92.0 Beta Version of Blender.
Glad for any ideas on this.

do you mean that you can move it like this? https://youtu.be/DTSKkG6HvFo

if the answer to my comment is "yes"...here is the solution for geometry nodes:
just add a transform node before the boolean operator and connect the translation to your group input node. Of course, if you need rotation too you can connect them as well.


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Black Spots and Corruption During Mesh Edit
When I operate on my mesh, black spots and glitches appear. All the normals are aligned correctly and the UV is clean with everything in the right place. Here is an example of what happens when I seperate some faces;

Notice the triangular blotches on the edges.
Here is an example of subdivision on the mesh;

And again, similar corruption occurs when I delete doubles. I have no idea what could be causing this. Can anybody help please?

Interesting. If I clear custom split normals data, then subdivide, then press add custom split normals again, the effect goes away. I've still no idea what's going on. I shall have to read the docs on split normals (whatever they are).

All right I don't know. I guess the problem bred from the software I used to extract the model (Ninjaripper). It created a weird data layer of normals information (sharp-edge, smooth-face, etc) which doesn't show up in the viewport edit. It makes precious little sense to me, and the man-pages aren't very clear on the subject at all.
The fix as I mentioned above is to remove the data layer before editing, then replace it again afterwards.
Run it up the flagpole...


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My mesh freaks out when I rig it, i think because it's made of separate pieces
I'm having a problem with the rigging in my mesh. I made it by adding cubes in edit mode to make the different body parts.

So anyways, when i made the armature for the mesh, an error popped up. It said "Bone heat weighting: failed to find a solution for one or more bones". I can't manage to make it work.

In this next picture, i rotated his left leg back 90 degrees and his right leg 45 degrees. The left leg moves both and the right one stretches the body. The head and arms stay where they are no matter what i do, also do the hair and cap

Any tips? I've been looking for answers but none of them seem to help with my particular issue

Its possible you have the weights assigned twice. I would recommend separating your object out into its constituent elements as well. extremely related

Before you apply the armature, make sure your character has no modifiers. You can check this by selecting the entire character and hitting [alt]+[c] and convert to mesh from curve/meta/etc. If you're getting an error message about bone heat weighting, make sure you remove all doubles (select all verts in edit mode and "remove doubles" in tools panel) and clear the normals [ctrl]+[n] in edit mode.
This is explained very well in the following video
Blender-Fixing Automatic Weight Errors
If none of that worked, try separating the mesh into loose parts (select the entire mesh and [ctrl]+[p] in edit mode) and apply the armature while all the loose parts are still selected.

Did you check whether the mirror modifier is applied or not and if the armature modifier comes first in the modifiers tab of the object?
If there are any modifiers active except the armature modifier I would try to apply those first.
Also, you can change to weight painting mode and assign the bones manually to certain vertices. But you might know this already.


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Assigned material has jagged edges
So basically when I assign a material to selection, because of the faces being grid-like, the material will have a really jagged zig zag edge. How do I get around this?

Use a texture or some other method, then just materials based on the mesh.

Please see @Qutorial 's answer here: http://blender.stackexchange.com/questions/516/add-different-materials-to-different-parts-of-a-mesh The best way in this situation is to use a b&w texture as a mask for mixing two materials as David said.

One way you could work around this is by using the knife tool. this can cut the white squares around into triangles that can be used to make the material flow a little better. you can do this by pressing k and then cutting out the shape. This should make it so you can have a better looking object. If you need any help with any of these steps, just ask.


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Smoothing out angular object in blender?
I imported this object from an .stl file which I created in SolidWorks. I need to export it in a .raw format for further use. But the object is a bit too angular. Is there any way I can smooth it out using blender?

Thank you

In the object mode select the object then there is option "subdivide surface" in the "Add Modifier", as shown in figure at right by red color point 1, after selecting it,
Click the view untill "view 2" as you can see I have View 1 in point 2 written in red color
At left you will see the smooth the press that smooth option

I was looking for something like this! Thank you.

This will introduce far more geometry than is needed. See my answer below for a better approach.

Even if you don't want to do this much just go to "object mode" select your object then just click "smooth" at left. No much work needed. BTW I am new to blend therefore provided you what I used with my experience. ;-)
Thanks @pycoder, this is really good to know!!

There is no need to introduce additional geometry here. Use smooth shading, then turn on auto smooth in the mesh settings.

Download the blend file

I don't think that would work. The file is going to be exported as a .raw file which doesn't support smooth shading, let alone Auto Smooth.

@ScottMilner Just adding geometry is not the correct way to accomplish this. If you are sure that the .raw format doesn't support normals, then the proper solution would be to adapt the shader used to render it from the end of whatever imports it. The "more geometry" solution won't fix the problem...it just makes it look better. Incidentally, the other answer uses smooth shading as well ;-)

I'm not sure what @menrva's purpose with this is, but the .raw file is just a list of 10 numbers per face: three coordinate points and a normal vector per triangle. If they are wanting to render it, then your solution would be fine. For 3D printing, though, more geometry is the only solution. Also, smooth shading doesn't change the outline of an object, and the sharp edges could still be seen in close up rendering.

@ScottMilner Interesting about the .raw format...I've never used it before. Regarding 3D printing, that is correct, but the two scenarios that you gave are very specialized, so my answer still works as a way to do this. On the other hand, a plain subsurf modifier will not have the correct form at all. You need bevel or edge split, etc. to make it work.


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Is there an addon or a trick to prevent objects from being placed inside of each other?
I was trying to make a big cluster of balloons but it toke to much time to place every balloon in a random position without them intercepting. Is there anyting that can prevent this, like an addon that prevents objects or vertex groups of objects from intercepting?

Do you mean in the final animation, or while you're editing the scene?  I don't think there is a limit distance constraint for groups. I agree with @HybridLizard, simulation will be the way to go, if it's a large group of balloons. Alternatively, you could use balloon as particle, and set the particles to no-intersect.

You can use Rigid Body simulation, maybe combined with some forces to distribute balloons. That may take some time and experiments to make it right.

You can automate that by mass copying rigid body properties from one balloon to others. Please check Blender docs to know more about Rigid Bodies and Force Fields.
You can automate your work by writing small python script. Please note that a lot of commands you need can be taken from the console.

Depending on how "big" number of balloons you want using a particle system for instancing balloons can be quite good solution. To make balloons more diverse, there can be made several versions of them and grouped. Then you just need to use that group for instancing and adjust settings like number, size variation, etc. Unfortunately Blender currently does not directly support Rigid Bodies for Particle System instances so they need to be converted to objects first.


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Where is the UV vertex pane located?
I would like to follow a tutorial video. In this tutorial, the author uses the UV vertex pane:

However, I don't find it.
How could I bring this pane up?
Thank you very much.

Just press N key

@DuarteFarrajotaRamos When I do that, a pane does pop up, but I don't see the "UVs" section in it. I do see the "Display" section, but unlike the screenshot, above that I see ""Item", and above that "3D Cursor". I'm in edit mode, and on the left side I have selected "UV/Image Editor".

In the UV window on the left side, it's necessary to press N again.
Unless I do, the window on the left side doesn't have any pane.
What I thought was "the" pane was a pane of the 3D view window on the right side.


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Unity 3D RMB / Flythrough in Blender
When I hold down the right mouse button in Unity 3D, I can rotate around the current view. I THINK (this may be wrong however) that this is called "Flythrough".
I haven't found the name of this function in Blender so I couldn't change the "shortcut" for it.
I wanted Blender to navigate like Unity.
How could I make the right mouse button in Blender act like the right mouse button in Unity?
Thank you.

There is a Github project located here:
https://github.com/niusounds/Blender-Keyconfig
I followed the instructions given on that page, and I had an 1:1 navigation in Blender as in Unity.

I haven't used Unity for years but I believe this is what you are referring to.
It's here in 'User Preferences'(CTRL+ALT+U) -> 'Input' :

Do this:

Then WASD for movement forward, left, back, right and Q & E for up and down. Shift will make movement faster and ALT slower.
You will have to click the Left Mouse Button to accept the movement and not return to starting point.
Hope that does the trick for you. But the tmighty's answer looks more complete in terms of mirroring Unity navigation, if that is what you are after.

Scroll up/down in fly mode will increase the speed permanently, I important a big world once and wondered why the fly didn't work... it just was so miniscule, that not even "shift" made it any better


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I want to do -Back to the future- like flame stripes
Im currently trying to recreate the flame stripes from Back to the future.
I only need a still frame.
This is what i want:

And i only get this working with a basic fire sim:

Is there a good way to recreate these specific flames ?
Maybe even without a fire-sim ?

I think you're on the right track with a fire sim, but you might want to bump up the resolution. Also a wind force field might not be a bad idea. See the manual for some examples.

Final:

Emitter:
For Emitter/Flow I've used two Planes with some Loop Cuts sized differently to have random fire width. Important thing is here real world scale. Both of them are 10m long and ~15cm width. Scale applied (!).
I've assigned Transparent material to them so they are not visible in render.

Domain:
Domain has pretty high Resolution along with Smoke High Resolution. Settings like below.
Material is simple, without smoke.

Wind:
Last part is Force Field > Wind with some Noise.

If you need any specific explanation, please ask in comments.

this already looks really great. Thanks you. Is there to seperate the flames even down to the emitter ? In the BTTF-Photo the flames are clearly seperated. And in the fire sim they always fuse to one glowing blob near at the emitter. Also they emit from everywhere. Is there a way to add maybe a noise texture to control the emission  ? Or will i need to do multiple separated emitters for that ?

@JensClar sadly this blob is a "feature" and only way to reduce it is to set Flow source > Surface to minimum (0.5). You can also change width of the emitter to something really low, like 1cm or even less to have it smaller. Another method would be to just lower emitter below ground plane. Sadly again you can't use textures with smoke/fire sim to have some noise. I've showed you the way to vary thickness of it, but you can make more emitters if you want. Mantaflow simulations are pretty close to be in Blender 2.8, this should help with those issues. For now we have what we have...

ok i have not worked on this since you posted your answer. But how do you get the transparent input in the color ramp ?

@JensClar when selecting color in Color Picker, use A value to change alpha (transparency). https://docs.blender.org/manual/en/dev/interface/controls/templates/color_picker.html


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Zooming in dope sheet. Change to zoom at current mouse-position?
In 2.79 in the Dope Sheet editor.
Is there a way to change the mousewheel-zoom style from: "Zoom to the middle of the track."
to
"Zoom wherever the mouse currently is ?"
Coming from video editing, this seems much more intuitive

This function was added in 2.8


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Texture paint stops working at shallow angle
Texture painting stops to work when the angle to the surface you are painting on is to shallow.
Shallow Angle:

Larger Angle

Can i deactivate this ?
Or decrease the angle, after that it doesn't work anymore ?

You can turn off Occlude and Cull and Normal and then you will not have a problem painting at any angle, but that may or may not be what you are after.


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Reduce the brightness of a lit area

This room is currently lit, with a sun light and to a large part by the resulting bounce light.
I currently like the amount of bounce light, and how it shapes the light in the room.
BUT:
I want to reduce the brightness of the directly lit areas.
So i can whats happening in the areas that are directly lit.
Like that: (reduced sun-srength)

Is there a way to reduce the brightness of directly lit areas without reducing my sun-strength ?
Yes im usic the Filmic colour space.

You could render it with passes enabled and reconstruct the image with compositing. You then have the control of how much direct or indirect light you add to the compositing result:

you are my hero. I knew this had to be an essentiell feature. Thanks so much :)

this doesnt allow for denoising tho :( and since im doing an animation im kind of reliant on it

It is possible to de-noise with nodes. Since Blender's de-noising isn't something miraculous I think one can achieve similar results with Bilateral Blur node used on noisy passes. That would even have some benefits - de-noising after render is complete, so less experimentation, also does not need to use as much memory at render time with big tiles. But that's another question.

The easiest way is using some post-processing in the blender's compositor. There are nodes there like curves, color balance, which can easily isolate the highlights. Consider that in the compositor you have your "overexposed" areas really bright, but not clipped, because of 32 bit pixel color range, so you can map your colors along with the filmix mapper the way you want.
Also to isolate highlights you can use direct render passes being separated, darkened, and then combined back to the resulting image.
And another way is to cheat the renderer itself, with no compositor. You can add to your scene another sun, almost the same as your main sun, with the same settings, but make it to emit darkness instead of light. Setting its energy to a negative value will do the trick. And to keep the scene's indirect light unaffected, you have to set Max Bounces for this dark sun to zero. Here is how it looks like. (no dark sun; 50% darkness; 80% darkness respectively):


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Make Object emit light & be reconizable
i want an object to emit light, but still be recognizable as the object, like in this picture.

i tried using Luts in the colour management and tried to make only a second, weaker emitter be visible to the camera.
The problem is, that as soon as the object is emitting light, doesnt matter how strong, its not recognizable as 3D-object anymore.

I also tried to plug the node into volume and not surface, but then, it gets  transparent.
please halp
much thanks

It seams for you as 2D object (not recognizable as 3D as you wrote) because only one Emission shader plugged into the Material Output will emit light evenly from any surface point which is unrealistic. Provide other shaders mixing them with some factors and you will get more uneven lighting which will be more interesting. Final shaders mostly depend on the desired result

Here's a variation on Jens Clar's answer.  You can connect the output of the Emission shader node to the Volume input of the Material Output node.  Here's an example using the Translucent BSDF node connected to the Surface input of the Material Output node:

Here's the node setup:

Final:

Overview:
This method is based on Ray Length and Translucent shader. It's basically fake SSS shader. You can think of it as "light edge detect".
Exaggerated result:

Node setup:

Math > Add node control edge width.
White Emission shader control edge color.
Greenish Emission shader control light and mesh color.
Translucent shader is needed to calculate Ray Length, also could influence light color.

This is a great answer, but wouldn't the edges be darker than the rest of the object usually?

@MicroMachine well I've just made it as in the OP example. And as for physically accurate result I think it depends on how the light source itself is made.

have you tried to mix emit shader with a regular one, perhaps?
Here is a very basic example:

only works with simple objects and low emission

If its possible to put a lamp inside the object, you can also put a lamp into it and use translucent shader.


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Setting up UV direction
I have created a hallway in Blender, and then I applied "Smart Unwrap":

The unwrap doesn't look absolutely perfect, but I thought it would do the job.
Then I exported the model as an fbx and imported it into Unity.
In Unity, I applied a material to it which has a texture assigned.
For some walls it looks fine, but for some walls, the direction of the UV map is changed for some reason, and the texture doesn't look right:

How could I set up the "direction" of the UVs in Blender and not just hope that it will work out alright (which it obviously doesn't)?
Thank you very much!

You can use unwrap with project from view since your object is perpendicular, with view from specified angle and orthogonal view as well.

@Hikariztw Could you perhaps elaborate on what I should do to make that work? When I'm in side-view, it unwraps the side-view. How could I get the rest to get unwrapped, too?

I'm using Sure UVW Map (with UVW Box Map) to unwrap my architecture, it works great:
How to UV unwrap a wall to get a consistent texture?

When you do Smart UV Project you can generate UVs with islands.  Then you can select the pieces that need to be rotated and rotate them by pressing R 90 Enter.  You can also scale the pieces generated by pressing R 90 Enter.


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Rotating an object according to geometry
I have purchased a model.
This model is rotated for a promo rendering.
I have tried to rotate it to a zero position manually, but I find it both time taking and just not perfectly accurate.
Does Blender provide any way to automatically rotate an object to its geometry?
Thank you!

There isn't an 'automatic' method, because we don't know what rotations have been applied when importing a model.
But there are a bunch of different methods for aligning a model in some way. Here is one:
Identify a face on the model that you want aligned facing one of the global axes. Select that face and align your view to the face in the orientation you want it using the Shift+Numpad short cuts or the view menu. Aligning your view to the Top of the face (Shift+Numpad 7) will result in that face being aligned to global Z when you're finished (use Left and Front views if you want to align to X or Y).
Snap your cursor to selection and keeping your view aligned switch back to object mode and add an object (a cube is fine). Make sure to choose 'Align: View' before messing with anything else.

Aligning the new object to View will give it the transformation rotations that the face would have to have gone through to be where it is compared with the global 'world' orientations. You can now simply select your original object, then the new object and join them (Ctrl+J). Then clear rotations and it will be aligned to what ever global axis you wanted. Obviously you then delete the cube in edit mode.
There is some way to do this using custom transform orientations (2.8: The + button in the transform orientations drop down) instead of adding an object. But I don't remember how, so maybe someone else can post that method.

I'm using Blender 2.8. When I add a cube, I don't see your "Align" property anywhere. Where would I find it?

I got it according to this answer: https://blender.stackexchange.com/questions/149566/where-is-align-with-view-for-new-objects-in-blender-2-8/149575#149575

Can you have a look at how I could do it with a grouped object? I have uploaded my grouped model here, and I don't see how I could apply your answer in this case. Thank you! http://pasteall.org/blend/index.php?id=52238

@tmighty I think you mean parented (grouped is something else)? You should be able to use the same method, but instead of joining the objects you would set parent. In your example file you would parent your top level empty to the new object, then remove the rotations from the new object and clear parent on the empty making sure to 'keep transforms'.

Thank you, but it's hard to understand what I should do. Would you mind describing the required steps in a new question? This would help me a lot: https://blender.stackexchange.com/questions/149745/aligning-a-grouped-object-on-the-global-axes   Thank you!

Kinda depends on what you mean.  A model is composed of a lot of geometry.  Is there a specific face you want facing front?
If so, try this:
Select a face.  Ctrl-alt-space to create a custom orientation on the basis of that face.
Object mode, snap cursor to selection.  Create an empty.  Duplicate that empty.  Move that duplicate 1 unit in the custom Z.  Give the original empty a locked track (lock Z, probably) targeting the duplicate.  Parent your mesh to your original empty (keep transform).  Delete or mute the empty's constraint.  Unparent the mesh (keep transform.)

That's assuming you're already oriented properly up/down (Z axis).  If you're not, you can use similar techniques, combining a damped track and a locked track.

Hey, that's clever!

@Nathan Thank you, but I'm using Blender 2.8. The shortcuts don't work this way anymore.

They do if you chose "2.7 interface" at initial startup-- that's a 2.8 screenshot I gave above.  Can't tell you what your particular hotkeys are, but you should be able to figure it out with a bit of googling.  The only one I gave a hotkey for was "create custom orientation" anyways.

We have no context for what kind of "geometry" your model has because you have told us nothing about it. So the best we can do is offer examples that might not be relevant to you.
First consider a plane. A plane might be considered in "zero-position" (as you are implying) if its normal is parallel to the Z-axis. We could rotate any plane in arbitrary orientation to "zero-position" by measuring its X and Y rotation offsets and rotating about both axes by the negation of those values. But this is challenging because Blender's default floating point precision for measuring tools is only 4 decimal places (if I recall correctly). Blender's internal precision much higher though. I am pretty sure you can change your preferences to get more digits returned at the front end.
No tool native tool exists to automatically "undo" rotations but it shouldn't be difficult to implement one for somebody already experienced writing Blender scripts. We would just need to identify a line segment (or two vertices) to be aligned and an axis to align it to (the Z-axis, in the previous example).
The above criteria should work for objects with distinguishable poles (like UV Spheres) or planar features, but "right-side up" would be relative to the edge/vertices the user chooses to align.

This video helped me perfectly: https://www.youtube.com/watch?time_continue=87&v=NEUa1IA7NBQ


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Creating a polygon plane with different sections / components
I'm trying to build a polygon plane exactely as in this video at 5:28, but in Blender, not Maya.
I haven't found any convinient way to do that. I select the edges and extrude it, but I don't think that's a good way.
Could somebody suggest me an efficient way to do that?
Thank you very much!

do you mean several successive extrusions? you can do one extrusion the repeat the operation with shift R for example.

Create the plane, Edit Mode.. 'W' menu > Subdivide?

@moonboots Thank you, I would only like to subdivide in "one direction". For example, my 2x2 plane should become a 2x4 plane.

you can use ctrl R to create new edge loops, or select an edge loop and ctrl B to create bevels, each time use + or - to add or subtract the number of edge loops... there are many ways of doing it... you can also do as they do in the video, duplicate and snap

perhaps what you want is to keep squares?

...another way, in Edit Edge Mode, Ctrl-Alt select an edge (which will select the ring of parallel edges) and Ctrl-E 'Edge' menu > subdivide

I suppose you want the extrude part to be strict squares. Here are some ways to do it (among others):
1)

Create a plane and create an edge loop in its middle with a ctrl R.
Scale your plane on the same axis, for example 3 times (S Y 3).
ctrl Rand + to create as many edge loops as necessary on the orthogonal axis.

2)

Create a plane and Subdivide it for example 5 times (use the parameters on the bottom of the left menu).
Delete a part of the plane so that you have the length you want.

3)

Create a plane, subdivide it, enable the Snap option and its options.
Duplicate the first subdivided plane as many time as you want, the Snap option allows you to stick to the previous copy and to merge the vertices.

4)

Subdivide a plane
Add an Array modifier and choose the Count you want
Apply the modifier in Object mode


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Can an object be automatically rotated?
I have a pistol model whose rotation is a few degrees off:

Does Blender have a function that would automatically fix the rotation and "align" it according to the object's geometry, perhaps like the 3D cursor to Selection option?
Thank you!

Related https://blender.stackexchange.com/questions/63506/set-object-local-axis-based-on-face-orientation

Palkonimo has the basics of it right, but you can accomplish the same thing more quickly using Blender's built in snap options.

Begin by picking two points on your model that you want to line up with an axis. Move the 3D cursor to one of those points.
Duplicate that point, and move it away along the axis you wish to align to.
Select the other of your chosen points on the model as the active element, expand your selection of the model using L or Ctrl +.
Rotate, using vertex snap to active element, and target the vertex you duplicated earlier.

Neat... You could also add that you can define the axis you want to align to, (if it's not conveniently world X,Y or Z,)  by creating a Custom Orientation from an existing edge, and  moving your snap-target-vertex in Y of that orientation.

I think there's no way of automatically doing it. Yet would be a nice addition, though you'd still have to select an edge and an axis that ought to be aligned.
Nevertheless, you can do it manually. As you can see in the image, there's a plane rotated a bit. I want to align it "according to it's geometry". This means that I have to select an edge and an axis that I want to align. In my case I want to align the selected edge with the y-axis. And from the drawn triangle we can derive the angle that the plane has to be rotated.

We just need to know the lengths of two of the triangle's sides. Since you know the position of the vertices, which are also two of the corners of the triangle, we can just calculate them:
In my case the length of the red vertical line is the difference between the y-coordinates of the vertices: 0.759317 - (-1.193079) = 1.952396
The length of the red horizontal line is the difference between the x-coordinates of the vertices: -1.193079 - (-0.759317) = -0.433762
Now we just have to use some trigonometry. With a being the angle we are looking for: a = arctan(-0.433762/1.952396) = -12.525905490885°
In this gif you can see that it is now aligned after rotating it that exact amount:

Now, this is just an example. In your specific case you'd probably choose an edge on the pistol's side and align it to the z-axis. Then do the same math: get the difference of the z-coordinates for one, the difference of the x-coordinates for the other side. Then use the arctan to get the angle and rotate your weapon along the y-axis.


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"Baking" spline
I have downloaded a great model of a chainsaw.
The author of this model seems to have created the "teeth" of the chainsaw with a spline, at least that's what it looks like to me. Here is a screenshot:

I would like to use the model and its teeth in a game, so I would need the shape to be "baked", I think.
When I delete this object, the teeth look like a flattened line::

Could anybody please tell me how to "bake" the spline so that the teeth stay in the bent position even after I exported the chainsaw as an obj or so?
I have uploaded the project here:
http://pasteall.org/blend/index.php?id=45905
Thank you very much.

Teeth selected, look at the right in the property panel and in the "modifiers" tab. You will see a "curve" modifier. Click the "apply" button on it.

Alt+C and convert to mesh.

Both work great, thank you, you two! I don't know if both do exactely the same, but they both did the job. Thank you again!

@tmighty - using convert to mesh on a mesh object will apply all modifiers, so yes it should give the same result as manually applying them.

So, as @sambler said, In your case, this is not exactly the same as your object has two modifiers.

Can  anybody tell me how to animate this in Unity 3D? I guess that extends the scope of the question, but I thought I might ask anyway...


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Merging all materials
I have a project where several materials use the same texture.
I would like to have only a single material.
I have uploaded my project here:
http://pasteall.org/blend/index.php?id=45922
Could anybody please tell me how to do that?
Thank you.

Your materials are not all the same here. "rubber" does not have the same specular value. But except that, if you only keep the material named "body and teeth", that should make the job. Use the "minus" sign on the right of the materials list to delete each.

Please use http://blend-exchange.giantcowfilms.com/ for blend file uploads. It is more permanent that pasteall.


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Follow Path Constraint with Object with Array and Curve modifier not working properly
I can't get the stars to follow the path. Tried everything I found in other questions to no avail.
here's the file

You've given a Follow Path constraint to your object as if it would act as a third modifier but it won't, it will just move the object along the path and the object will be affected by the modifiers independently. So I guess you have 2 possibilities: Either remove the modifiers, convert your star to mesh, give it modifiers again, and keep the constraint so that it moves along the path. Or, if you want to keep your star as a curve, remove the constraint and, in order to move along the path curve, just move the star on the X axis.


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Snapping multiple vertices from one mesh to the z axis of another mesh's vertices
I have a mesh that is mountenous terrain. I also have an svg dataset with the houses that belong on that terrain. But that second dataset has no height invormation. Now I got my mountainous terrain as one mesh in blender and I imported the svg data as one mesh.
Is there a way to snap all the vertices from the buildign data set mesh to the surface of the topographical mesh without doing one by one? There are tousends of houses.

Related https://blender.stackexchange.com/questions/174727/place-objects-on-mesh-using-snap-with-python-script  Since houses are generally level to ground a method is to set origin of house to ground and shrinkwrap it and a "skirt of verts" to surface, to make it look like it is on a flat foundation,  rather than overhanging.

The Problem is, my houses are not objects, It's one entire mesh. So I would need to tell the vertices of the buildings-mesh to place themselves on the z axis where to topographic meshes vertices are. But I am not that well versed in Python for Blender.

Can they be separated eg P Loose Parts ?


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Is is possible - Refraction Shader without returning black?
So I`m trying to create fake refractive material without any reflections in Cycles, and I have already tried all tricks, is there really no way to get rid of these black zones?
I used Vray and Corona before and never had problem with that
For comparison - simple scene with a solid single color background, in Corona object is totally transparent so I had to add box behind to see it, while in Blender Cycles thosee black zones always appear
I`ve already tried increasing bounces, different mixing options but nothing gives the result at least same as corona or vray with 0 reflection/full refraction

I think there is a physical point of full refraction (or absorption) unless you turn the refractive index down to 1.0. If Corona already works like you need it to, I would stick to Corona.

Ray depth greater than desired number -> transparent bsdf, but in this environment it's going to be hard to see what refraction is doing


text:
Micro displacement not rendering with motion blur. (Blender 2.79 )
Most of the bee is animated, specifically the wings, each flap is around 3 frames so there should motion blur happening at least with the wings.
I've attached the pertinent screen shots of settings as reference.
I've also tried rigging a primitive object with bones and animating it next to the bee with the same settings which does render with motion blur.

I don't think that rigged animation gets motion blur at the moment only over all object motion. Perhaps if the wings were separate objects? Also with such extreme blur, its better to fake it. That's what happens with helicopter blades and plane propellers. Maybe a volumetric shape would work and render quicker? Only issue would be lack of glint from surface of wings in a volume (no reflections)

I've tried it with another mesh it does render motion blur on deformations, just not on this mesh.

Attached a primitive example above, made in the same file.

motion blur in blender is calculated based on the previous frame positions. so blender should load the scene for 2 frames to calculate motion blur, essentially to calculate motion. Adaptive subdivision is a heavy process and i believe happens only on the frame you are rendering so it has no data for the previous frame.

As of 2.79, Cycles does not support adaptive (micro) subdivision and deformation blur on the same mesh. You should uncheck "adaptive" on the subdivision surface modifier if you need deformation blur.
See this documentation page from the main developer of this feature: https://wiki.blender.org/index.php/User:Maiself/Micropolygon_Displacement

A reference would make this answer much stronger...

I would suggest to change Shutter type to None. I'm not sure why, but from my experience, Top-Bottom doesn't give blur with motion based on rig bones movement (like flapping wings f.ex.).

Forgot I turned that on, was an attempt to get a result when None was producing none lol, still no go though

Weird. Why would one object produce blur and other not in the same circumstances? Are the origins of the armature and fly there or in center of the scene (0,0,0)?

I got it to go by turning adaptive subdivision off in the modifier stack, is that not supported?

You should probably answer your own question with your solution so that others can benefit, sometimes these replies are hidden from view.

Yeah, you definitely should place your solution here as an answer. It's pretty unusual problem, and knowing it surely will be useful for someone else too.


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Embedding vertices onto a plane
Say that I have a collection of points, as shown below with the circle, and I have a plane that I want to merge them onto. The points and plane are perfectly parallel, and the end goal is that the plane I'm merging onto doesn't move. Is there a way to do this? I think it could be done in a roundabout way with a boolean modifier, but there must be a better way.

Related https://blender.stackexchange.com/questions/15687/making-holes-in-a-mesh/ or https://blender.stackexchange.com/questions/50538/how-to-cut-an-object-along-a-curve


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Once mirror mesh is made - how to remove its data from the original mesh
I have downloaded a female model
https://www.blendswap.com/blends/view/26755
from net and it is made with mirror. so when I try to rig it the left side will only follow the right side. How can i make the left mirror side its own mesh - and not follow the right side.

apply the mirror modifier?

I have tried turning off the mirror modifier and it removes the left side.

Try this : Go to modifier tab setting you will see 'apply' button on the mirror modifier setting.

WhenI try to click apply it says "modifier can not be applied to mesh with shape keys."

After using shape keys, your mirror modifier can't be applied, unfortunately. There's a way to recover from this situation, maybe, I'll try to describe it with a simple "cube" example.
Here is a simple half-cube with X mirror modifier, and a shape key setup.

The shape keys affect only the "real" part of the mesh, and the mirror cannot be applied. So, I'll

remove the mirror modifier
duplicate the half-cube (SHIFTD)
scale it over X with -1 factor (mirrors over X the duplicate half-cube) using SX-1
note that each half-cube retains its shape keys, mirrored

Finally, I:

join the two half-cubes (CTRLJ)
they became a single object (you could remove duplicate vertices at X = 0)
fix, in edit mode the normals, recalculating  them outside (CTRLN)

And now you have a single object, symmetric over X, with shape keys acting as if they were mirrored...
Of course, if you wish your model to behave differently on the left and right side (which was the primary reason to apply the mirror modifier), you could not need the shape keys of one side to be "duplicated mirrored" on the other side... in this case, before joining the two half-cubes, remove the shape keys from the duplicated half-cube...
I hope that this can be easily applied to your half-model too!

Thank you m.ardito this fixed the problem i was having.   :)


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Dynamic generated json file read
I have an external script that generates a json file with rotations. I want to read this json file with blender, but it seems there is a problem with the json reading functions in blender.
import json
from pprint import pprint

with open('blendjson.json') as data_file: #This line throws this error : "Python script fail, look in the console for now..."
    data = json.load(data_file)

coordx = data['coordx']
coordy = data['coordy']

#This works as long as I can get values for the varibales coordx and coordy :
bpy.ops.transform.rotate(value=coordx, axis=(-1, -0, -0), constraint_axis=(False, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='DISABLED', proportional_edit_falloff='SMOOTH', proportional_size=1)

bpy.ops.transform.rotate(value=coordy, axis=(-0, -1, -0), constraint_axis=(False, False, False), constraint_orientation='GLOBAL', mirror=False, proportional='DISABLED', proportional_edit_falloff='SMOOTH', proportional_size=1)

This script works in itself when launched through the terminal (python blendjson.py), except for the bpy objects of course.
Is there a way to read the json file, or a better way to get these two variables ?

Obvious follow up question.... have you tried looking in the console for the actual python error being thrown (as it says in the error message)? In Windows you can open the console within Blender via the menu. For Linux you can launch Blender from a bash shell (or similar) and the output will be shown there. For Mac, I presume it's similar to Linux. That console output will tell you the reason.... most likely it's looking in the wrong place - depending on how Blender is started it could be running from within a directory you're not expecting... try using an absolute path to the file.

Indeed, the path was wrong... I changed for an absolute path, it worked "perfectly".

Instead of using operators to transform an object, it's better to just change its rotation_xxx properties directly. It'll be faster, you'll have more control over which objects to rotate, and it won't create unnecessary undo steps.

Thanks! I have another problem now. I want to check the file every x milliseconds. I can't seem to find a way to make threads or sleep work...

That is another question, so please ask it in another question. We'll be happy to answer that too.

As Rich has pointed out, the file you are trying to open does not reside at the location Blender starts up from.
By running os.getcwd() you can see, that you are working in the folder where you installed Blender to.
To open the file (which I guess is residing in your homefolder), you can use the os.path module:
os.path.expanduser('~')

This will give you your homefolder, which you can then combine with other directories using
os.path.join(direc1, direc2, file)

Another option is to use os.chdir(directory) to move to a new working directory first, before opening the file (e.g. you can use os.chdir(os.path.dirname(__file__)) to move to the folder where your python file sits)
Happy coding, Mr. Anderson!
Hint: When using different operation systems, make sure you always use the os.path module, as it can handle the differences in path separators ('\ for Windows, / for Linux and so on). E.g. os.path.abspath(filepath) to get a proper absolute path for the provided filepath.


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Blender running very slow
Blender is running extremely slow for me. I am just in the edit mode in the 3D-Viewport and just moving a few vertices takes like 4-5 seconds. I am working on very simple models and when I look at the performance in my task manager my GPU stay under 10%, my CPU is around 20% and I am using around 30% of my memory.
The same project ran fine just yesterday.
What I have tried:
- Restart Blender
- Restart PC
- Check for updates of basically everything
- Activate CUDA
Running:
v2.79
gtx970m
i7-4710HQ
16 GB

Do you have any modifiers on your project? If so try hit the little eye icon, so you cant "see" it. It will still be rendered, but your pc wont have to work so hard while you are still working on your project.

Double check if you're not running through an animation (hit Ctrl + A to pause play animations if you don't have the timeline up).
If that doesn't work, grab DDU uninstaller from guru3D here (http://www.guru3d.com/files-details/display-driver-uninstaller-download.html) and uninstall all your NVIDIA drivers. This thing wont erase the CUDA toolkit, so don't worry about that!
Let me know if it worked, otherwise we can go from there


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How to make material from multiple objects appear as one. Ignore interior faces?
I'm struggling with a what seems like a simple task, both in an animation sense and a 3D printing sense. I'm attempting to create a model similar to what I'm showing here that would allow me to take a point source of light and run it along the interior of a "blue glass" material. Here's my steps so far...

I created the circles with the circle curve.
Added depth to them, made them full, etc. in the object data panel.
I converted them into meshes.
I joined them all into one object.
Used edit mode to remove and doubled vertices.
Created a larger square and did an intersect boolean to attempt to
get only a single layer of mesh...didn't work.
Created my material and added lights.

You can see when I have the light in a part of the model that has no interior faces then it fully shines down the tube. When it's behind or in an area where there are interior faces they occlude the light.
Is there anyway to make Blender behave as if the whole object is solid even if it isn't? I understand the best way to achieve the look I'm wanting is to have no interior faces, but that seems to be an impossible task given the modeling that I'm doing. This example is a heavily simplified version and the full model has many more layers of circles at descending sizes.
I'm also running into this problem with creating these models for 3D printing. The interior faces are a real problem that I can't seem to overcome.
I've got two images attached, one showing the lighting issue, the other showing a fuller version of my model. TIA

In any of these attempts, did you try to use the Select menu (in the header) to select Select All by Trait -> Interior Faces and then delete the selected faces?

This should probably have been a comment, but I can't create those for now...
If you want to combine objects while eliminating the interior surfaces, the boolean 'union' operator seems the most appropriate to combine your circles. This operator removes internal faces (creating vertices where needed).
It's probably going to be quite fastidious to do, unless you can do it in stages where you combine a few tori, and then duplicate those units (e.g. create units of 4 red circles and one purple).

Yeah, boolean was my first attempt. Utterly fails in most of the unions I need.

there are two algorithms for the union operator, one of them removes interior faces, the other doesn't


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Snapping doesn't work when moving UV Vertex to 1001/0-1 range
I'm trying to move a group of vertices to the 1001/0-1 range.
In a tutorial I've read that I could make the vertices snap so that I can't move freely. This is what I tried to enable.
To do that, I checked the option "Display->Normalized".
However, I can still move the vertices freely, in the screenshot you can see that it's for example at X: 1.313, Y: 0.325
How could I make it snap well? I think a snap of 1, 1 could be good.
In the screenshot you can see that I tried other values, for example 100, 100, but that had not effect, I think.
Could anybody tell me how to enable the snapping that I'd need?

Do you want to make UV islands locked in the texture space boundaries? It's not clear how Normalize is related here

Yes, that's what I would like to do. The UV islands are already well organized, but they're for example in the 1002 range, so I need to shift them to the 1001 range. I read that "Normalize" would allow me to do so more easily. Is that not what is required here? Is there a better way to do what I want to do?

I can't tell for Normalize, it will just convert displayed values for position of UV vertices, not avoid any movement anywhere, but you can use UVs > Constrain To Image Bounds in UV editor. Scale islands a bit down while they are inside texture space and then scale up until they are locked from scaling more


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Scaling directly in obj file
I can scale my model in Blender at export, and that works perfectly fine.
However, I need to do this automatically as I have many models which should all be scaled to 0.01
Can anybody tell me which values I need to change in the obj file to apply for example a scaling of 0.01?

Ok, I got it:
I simply go through each line, and if a line starts with "v ", I mulitply each of the 3 values with the desired scale.
It should be noted that a scale of 1 is "100%", a scale of 10 would be "1000%", etc.

Code for @tmighty solution would be something like this. Can confirm it works:
def rescale_obj(obj_path, obj_scaled_path, scale):
    with open(obj_path, 'r') as source:
        with open(obj_scaled_path, 'w') as target:
            for line in source:
                taget_line = line

                if(line.startswith('v ')):
                    coordinates = [float(coordinate) for coordinate in line.split(' ')[1:]]
                    rescaled = [c*scale for c in coordinates]
                    rescaled_as_str = " ".join([str(c) for c in rescaled])
                    taget_line = f'v {rescaled_as_str}\n'

                target.write(taget_line)


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Get count of selected vertices in UV pane
I would like to know the number of vertices that I have currently selected in the UV pane.
The stats bar on top of Blender only shows me the overall vertex count.
How could I show the number of currently selected vertices?

If you enable UV syncing, selected UV coordinates will be echoed onto your 3D view, and the header will show you how many you have selected.


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Showing Hierarchy / Project view during UV editing
When I switch from "Default" to "UV Editing", the "View" pane on the right always disappears.

Is this intended for some reason, and if yes, for which reason?
Can I simply show it again? I haven't found any key combination for it yet.
Thank you.

You can re-arrange workspace layout areas at anytime. See https://docs.blender.org/manual/en/dev/interface/window_system/areas.html

That is intended behavior. The default UV Layout is set to have no outiner visible. As Carlo mentioned you can personalize it at will and save it in the default startup file.

But there is no easy shortcut to make the view visible again, right?

Blender's UI allows us to split the window into multiple sections, each using a different editor. These window layouts are saved as a list of Screens which we can switch between and add to. The default UV editing screen does not provide an outliner, or a graph editor or a properties editor or dopesheet...
There are three places that screens can be defined, the default screens programmed into blender, the startup blend that has your settings or each blend file that you use. When you open a blend file there is a Load UI option which decides if you want to use the screens in the file you are opening or keep the screens you are currently using. You can set the default for this option in the preferences.
Every time you adjust the window layout you are altering the current screen and that adjustment is kept in the current screen and saved with the blend file. If you don't like the default screens that blender provides you can define your own screen layouts.
You define custom layouts by starting blender, create and adjust as many screens as you want and then save your startup blend. This makes them available every time you start blender, if you also disable the Load UI option in preferences and save that you will use your layouts unless you choose to use the layouts in the file as you open it.


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Re-UV with SmartUV after scaling UV island
I have used SmartUV to unwrap my model (a dog cabine) in Blender. It works perfectly fine.
However, the "interior" of the dog cabine occupies a large area of the UVs.
I don't want them to take up so much space as the interior will have very little color details. A square of 24x25 pixels would do.
When I scale the islands manually, I would have to scale each other part of the UV as well.
Is there perhaps a function that would re-sort / scale the other UVs (which I have not scaled down manually) according to my changes?
I hope it's clear what I want:
I want to tell Blender that the interior should not occupy so much space, but it should still use SmartUV (which is such an amazing time saver for me).
Thank you.

If you have already interior unwrapped like what I assume is done on the screenshot then select UV islands corresponding to interior and move those islands away on UV map, then scale them down

Perhaps you could:

Select everything except the interior, then U Smart UV Project.
Select the interior and again U Smart UV Project.
Scale down and move this second unwrap where you want, or even, if you don't want to manage 2 UVs overlaying, give it a second material (with the same Image Texture).
Note that you could use Vertex Groups to facilitate the selections.
Also, in the UV/Image Editor, enable Keep UV And Edit Mode Mesh Selection In Synch so that you can see both the 2 UVs.

Oh man, you are a genius!!!!!!!!!! Exactely what I wanted. Thank you sooooooooooo much!!!!


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Moving in a straight line
For testing purposes, I have selected a face of a cube.
Then I dragged the face down using the green arrow.
It seems to have worked fine at first.
However, when I then rotate the view, I can see that it didn't work straight.
How could I ensure that using the green arrow will move the face down in a straight line?

I don't know if there is a way to achieve this with the green arrows, but it is done easily using the movement hotkeys. If you press G, the vertices will move freely. If you press x, y, or z after that, they will only move in that direction. But if you press G + Z + Z, it will not move in the global z direction, but in the local z direction, which is what you want here. For example, in the image below, I have a rotated cube, and I move 1 face not upwards, but in the direction that is it facing, by pressing z twice after pressing g.

I hope this helps!


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making a volumetric XYZ array in geometry nodes
How do I make a geometry nodes setup that does the following WITHOUT using the array modifier,

volumetric grid, of evenly spaced instances of a collection (containing two objects that need
to retain their transform data from the collection) in xyz space
the instances need to have random position transform introduced over time the value of which
needs to be animatable to give them the appearance of a wiggle, that's it.

I'm losing my mind over this seemingly simple aspect of a gig, its been days, I'm kind of at a loss over how complicated this has become, it seems like such a simple straight forward thing, is this possible?

I get worried by "how to do x without using y" questions.  There's a reason you don't want to use an array modifier.  What reason is that?  Because it's entirely possible I could give you an answer that doesn't use it, but that doesn't address that reason, and then I'd have wasted my time.

I'm instancing a alembic of a fluid sim, the array makes the instances duplicates and makes this impossible, I've found tutorial that kind of does this by building a width and a height node and then multiplying that but I cant figure out how implement the random movement I need,
https://www.youtube.com/watch?v=GD5n27m7_Yo&t=519s

Geometry Nodes has changed quite a bit since that tutorial, with the introduction of Fields, but the logic of creating a 3D array is still much the same.
The array is created by

Creating a subdivided line
Instancing a grid on each point of the line.

In this example, the count and dimensions of the grid and the line are controlled by the same parameters, so the overall bounding-box and the cells remain cubic.
The Grid-Instances are Realized, so the layers do not share point-IDs. This allows random distribution of the collection elements through the volume, not just per-layer.
In this example, - the available controls in the modifier interface are:

Count - The number of cells to a side of the cube
Cell Size - The length of the side of each cell
Element Bias - The proportion of each of the 2 elements in the collection represented in the array
Jitter Amount-The amplitude of translation from cell-center when the element locations are randomized
Seed - The seed of that randomisation.

This may not exactly meet your specification? You may want more control over the distribution of elements, or send a continuous noise-ripple through the array, rather than a random jitter.. etc. But perhaps this is a start.

(Blender 3.0b)

This is 99% of the way there! Thank you!
problems, I'm still having, my alembic instance now just show up as an empty, is there a way to instance the whole collection is it appears in the collection (a small mesh placed inside the alembic, in the shot its a particle of dust inside a rain cloud) instead of each object in the collection appearing as its as its own object per grid point?

excuse me a particle of dust inside a raindrop

I'm probably being dim, not very experienced with alembics. Do you mean each instance contains its own animation? You can certainly instance [whole collections] at  each point, rather than [picked children of collections], if that's what you mean.

that is correct, I'm definitely dim on the mechanics of how any of this works, what input node would I use to do that and where would it plug in?

I'm using an alembic export of a flip fluids sim with a static model nested inside of it, hope that clears that up

To get [Whole Collection] per point, that would be unchecking 'Separate Children' in the Collection Info node.. not sure about the animation.  You may have to provide an in-principle, 'toy'  example of what you're referring to, to be completely unambiguous.

I got it! Thank you so much! I'll post screen shots of the mod I did to your setup when I finish the project.

@o88 Great! It's nice to see results of suggestions :)

Let us continue this discussion in chat.


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Outliner locked me out, layers highlighted green, and many layers are hidden cant unhide
I accidently did something to my outliner that I can't find or figure out how to undo.
All of my layer trees are gone except one but all objects are in the 3D viewport. I also can't do anything in my outliner except go into edit mode for the visible layers and toggle their 3 options.

All layers are highlighted green.. I can't contract the layer trees that are visible and the other layers are there but are invisible.
I know they're there because when I go to object in properties, the drop down menu shows all my layers that are hidden from the outliner.
When I select one of those layers or object I mean, the outliner doesn't show the layer for that object. What does layers highlighted green in outliner mean?
I want control of my outliner back, how do I undo this?
thank you

There aren't any layers in Outliner, it shows object datablocks present in your scenes (in this case in the parented hierarchy).
Highlighted in green means results of the search:

Above green highlight shows everything which fits letter "M" in the search (which can be anywhere in the word).
Remove the search keywords and search filter won't be applied anymore.
Aside from that some objects in your scene are set as non-editable (White Arrows to the right from the object datablock name), which means they will be visible but not selectable. You might need to turn them on for further editing.

OMgosh... I feel so silly... thank you, I didn't remember that I had used the search.. I didn't see it either, on a 4K screen and is easy to miss. Thanks a bunch! You saved me from a lot more stress, thank you


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How to add a texture color specificed "glow" to a HUD panel?
I've been trying to figure this out,
I'm using Blender 2.79 and the new Principled shader but it doesn't have an  alpha channel or an emissive channel built in (yet?). I can accomplish what I'm trying to do below in C4D but I'm trying to switch entirely to Blender. I have a material that's called "glow" that gets applied to HUD and LED
type panels in a spaceship which has an alpha channel.
Here's a wide image of my node setup

I'd like to have the emissive match the color of the diffuse map (minus any black) and have the alpha applied so only the color in the diffuse is emitting light for this material.
If I have to create a modified tiff from the diffusion with alpha texture to make one specifically for emissive that's okay.. just want to know how best to accomplish this?
Thank you very much!
I'm new to blender and it's absolutely amazing!

Figured it out

Just had to plug the texture directly into emissive color instead of trying to use the output from the principle BSDF into emissive color. This works! Problem solved.


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Which Boolean Math mode should I use?
I always find the description within Blender interface or in the docs confusing:

Mode
And: True when both inputs are true. (AND)
Or: True when at least one input is true. (OR)
Not: Opposite of the input. (NOT)
Not And: (True when at least one input is false. NAND)
Nor: True when both inputs are false. (NOR)
Equal: True when both inputs are equal. Also known as “exclusive nor”. (XNOR)
Not Equal: (XOR) True when both inputs are different. Also known as “exclusive or”.
Imply: True unless the first input is true and the second is false. (IMPLY)
Subtract: True when the first input is true and the second is false. Also known as “”not imply”. (NIMPLY)

...And for how ridiculously few combinations there are for 2 binary operands and one binary result, I just draw myself a table, decide which results I want in the table and see which mode achieves that. So I decided to prepare a tidy cheat-sheet to make this process easier for myself and others in the future.
Node tree used:

Nice cheat sheet, although I don't find the descriptions confusing (admittedly I have never read them before). But studying maths and IT surely helps with understanding the variations.

@GordonBrinkmann As for the "confusing" part - a typical situation is where I want to combine two boolean settings, like "use simple algorithm" and "make convex", and then decide to do something based on those two settings... The reasoning from design perspective alone can be non-obvious, so by far the easiest approach is to consider all 4 possible combinations of inputs. Once I have that, it's not obvious which option to pick, because the mapping in my head goes in the opposite way :D

Some possibilities are missing. Two of them you can achieve by reversing A↔B:

And the rest is trivial because it's either a constant value (no boolean math) or a NOT of either A or B:

These "cheat sheets" you have made are simply truth tables. Here is a diagram I found online:

I suggest you learn the correct terminology and get used to reading truth tables, it's very easy with a bit of practice and will save you a lot of time. Looking at these tables for each gate is slow and should really be a last resort. Also knowing how these tables work allows you to construct your own if you have a particularly complex output you need to construct an expression for.
I'm also not sure what's confusing about the Blender explanations, they are straightforward explanations in prose and could hardly be easier to understand!

Just because those are truth tables, doesn't rule out that it's a cheat-sheet of them. Also you seem to contradict yourself in two consecutive sentences: "[...] get used to reading truth tables, it's very easy with a bit of practice and will save you a lot of time. Looking at these tables for each gate is slow and should really be a last resort." - so get used to doing it, or avoid doing it? And why would you need to construct your own truth table, do you mean more than 2 operands? Otherwise I literally assembled all possible combinations so no reason to construct more.

I honestly don't see a reason for this answer as it does not show anything new compared to the previously existing answer - only that your truth tables are designed differently...

@MarkusvonBroady I'm not contradicting myself. Learn how to read truth tables, memorise them, then never use them again, because using them is slow. I have never used such a diagram as a cheat-sheet because they're stored in my head, the diagram is purely to demonstrate that such diagrams already exist. As for making your own, if you have four input variables and two outputs then the easiest way to construct your boolean expression is via a 4-input/2-output truth table and/or a Karnaugh map. For this reason, learning how to read truth tables is valuable. But using them for 2 inputs is slow.

@GordonBrinkmann Well I don't see a reason for the question as it's answered by Googling "truth table" or "Boolean logic", or within the first five minutes of any logic class, which is what I was trying to get across (albeit more politely).

Okay, because you thought the question and answer were not worth posting you saw the need to post another answer instead of just commenting on it...


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Access previous field value using "Accumulate Field" node
I want to access the field value under the previous index (previously evaluated value).
The "Accumulate Field" node requirement is due to my need to access the value within the pass that it is evaluated; in other words, I want to access it before the last value of this field has been evaluated.
A simple example of the problem is randomizing the values, but making sure no two same values are neighbors:

A separate pass changing the duplicates using "Field at Index" node, would not only unnecessarily change all marked "2", but with random replacement would again risk some or replacements to be repeated, as well as risk the last "2" to change to "0", converting the second last digit to a duplicate.
In this specific case perhaps a workaround could be made: iterate over duplicates (if field at previous index = field at current index), adding accumulated 1 to each, and if the last duplicate turns out to equal the following field value, add 1 more. This would produce an excess of incremental sequences (3, 4, 5, 6, 7; 12, 13, 14, 15 etc.) which could be passed through some shuffled translation (e.g. {0: 5, 1:3, 2:0, 3:4, 4:2}) but this would still create a repeating pattern and turn out to be much more complex than simply accessing a previous field value, if even possible… As well as the problem doesn't always involve random numbers or isn't always as simple (problem inspired by this question, where I need to access 3 previous brick colors).
So, is there some combination of chaining and subtracting "Accumulate Fields" to get the previous field value?

Just now realized ( debugging) this ultimately only works if the resulting, fixed number can be accessed by the next evaluation, ultimately meaning the Accumulate Field node would need to access itself. This is not possible. Maybe I'll redact the question later to allow for some workarounds… I can't count how many times I struggled with this variations of this issue only to figure out it's impossible and then forget and struggle with it again…

If I understand correctly, you are still working on a solution that prevents the Random Value node from generating two equal consecutive values, right?

I thought about it. I don't quite get the "chaining and substracting" part. Do you have another example of this?

@quellenform the problems comes down to: have a function applied to a field, which can read the previous output of the same function. Unsolvable problem in geonodes so far…

Ah, thank you, now I understand. We have been at this point a few times :)

Of course since Blender 4.0 introduced Repeat Zones, you now can run things sequentially:

For the actual "accumulate" functionality simply add the current value to the former one, though in this case you have to resign from the -1 kind-of sentinel value and just use zero:

the purpose of this Q&A is to show that you can alter the value, based on previous value, within the accumulate field logic.
Of course you can both save "this" and "total", also because a node like "Store Named Attribute" contains a loop on its own, it's probably not efficient to use it like this on a big geometry, so consider implementing it by producing geometry (no idea if it's actually faster for any size of data):

And then you can sample by index from that geometry.


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Combine Texture Paint With Normal Map From MultiRes Bake
I have a Texture Painted Model that still has a MultiRes modifier active, and a normal map I baked from the multires. I'm trying to find a way to keep my texture painting and also incorporate my normal map.
So far my attempts have resulted in having one texture or the other (when "Use Nodes" is not selected in the material node window); see below:

When "Use Nodes" is selected with just about any combination of input and output connections I can think of, I just get a non-shaded figure like so:

What I want my model to look like is shown below:

Any ideas where I'm going wrong?

Turns out you simply need to make sure you apply a few options under the texture tab for the normal map image. With your normal map highlighted under "Texture," in "Image Sampling" make sure you check "Normal Map" and select "Tangent." Under "Influence" make sure "Color" is deselected and "Normal" is checked.

I back up Tyler on his advice.
Your node materials don't seem to be right for Node so I'd say ignore Node for the moment. One thing I learned just now while fiddling with texturing is to NEVER mix Node and non-Node materials and textures or Cycles and Blender render engine materials. It will give totally unpredictable results.
Anyway just in case you really have to use node for more complex effects, here is the pure Blender Renderer Node version of simple texture UV mapping with Normal maps. I advise not to build it on top of the material you have already created but rather start from scratch:

PS: sorry not really an answer but I can't post comments yet...


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How to Save OpenGL Viewport Animation in Blender 2.8?
I am able to create the viewport animation, and then play it back from the render menu, but there doesn't appear to be any option to save it. When I render from the camera I have, it saves to the path specified in the render options in the properties panel. However, viewport animations don't show up there. Very confused as to where that file is going to allow playback from the render menu at the top of the viewport.

I can't reproduce the problem. Both viewport render options save to the path specified in the Output tab in the Output panel.

You have to specify where the file is gonna be saved before you render it from the viewport! Otherwise it doesn't work, I had the same issue.

But how? What is the button/menu I need to click

@Ben Winding go to Properties->Output Properties->Output and define a folder

just like normal  animation  select the output file and hit render
and u will find the animation there its being playing from the output file


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Apply Transform and Rest Pose Not Working After Restart Blender
I've been working on a character model, and all seems well during a single session. However, after exiting and restarting blender, my model is scaled several thousand times larger than it was when I saved it, and the pose always defaults to this strange pose:

When it is supposed to look like this:

I can still use "ALT+G" AND "ALT+R" in pose mode to fix the pose issue, but "ALT+S" does not fix the scale issue. And in object mode, when I try to scale the model and armature back to the original size, the changes are not saved the next time I re-open blender (the pose reverts to the undesired pose as well). Even if I goto "object> apply> Location / Rotation / Scale."
Any help would be much appreciated. Thanks!

I determined the cause of the problem! I must have accidentally set a keyframe for the the armature scale and rotation! The strange part is that I never once placed the armature in that strange position, but I checked the graph editor and found keyframes on all joints. Once I deleted the keyframes everything looked good after saving and re-opening blender.

As mentioned in your question. Applying Transforms on the bones, would have actually been very harmful. Good thing you didn't do that.

Ah yes, I suppose I wasn't totally clear. You're right that it's harmful to apply transforms to bones while in pose mode or edit mode. I was applying the transform in object mode to the entire armature.

Don't worry, I understood. Just making it extra clear for future readers.


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Transparency Issue I've never seen [Blender Render]
So I'm using a mesh with a blushing texture that I hide in my character's head to create a blushing face with a shape key. I've done this before with no problem. This time I've run into a problem I've never seen. Parts of the blush mesh seem to cause any mesh behind it to become transparent when I turn on alpha settings, as seen below:

The only difference between this time and last is that I'm using a single texture for both the face mesh and the blushing mesh. Could that be causing the issue?
Here is the texture:

Here are my transparency settings:

I'm flat chat at present, but on the face of it you appear to be seeing the Viewport/OpenGL masking effect, in that a 'younger' & semmi-transparent object is masking out an 'older' object.  See here for the mechanics of this. (text under the 1st image)  I don't fully understand what it is you're doing here, but if you've got two different material slots for the same object, make sure the semmi-transparent one is at the bottom of the slots list. (use the little triangles to step them up and down in the list)  Any slot below the transparent one will be rendered invisible when the 2 are together.

Link for the above - https://blender.stackexchange.com/questions/117572/how-to-put-a-mask-into-3d-space/117941#117941


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How do I apply Movie Clip edits to my video sequence?
I did some stabilization using the Movie Clip Editor and tracking. I understand that what I have done is just in memory. How do apply the changes I have made in the MCE to my strip in the Video Sequence Editor?

@cegaton Thanks for the response. Is there no way to apply the MCE changes to the VSE? I am stitching together several videos, and will have to do this several times.

OK. I can understand that. If you post your comment as an answer, I will mark it as correct, after I have gone through the process.

I followed this video: https://www.youtube.com/watch?v=nU8zqn091rM rendered the video as you suggested, have no sound and the video is constantly zooming in and out very rapidly. It looks like an earthquake.

I used the Stabelize 2D node - I did make sure I pulled in the correct video in the node

In the VSE a Movie Clip from the MCE can have its 2D stabilise effect turned on.


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Change active selection from one object to another, with Python
I'm making a script to automate some steps I do quite often. In the script I need to change the active selection from one object to another to work on that object and then return the active selection to the first one, e.g. I have a cube and a circle, both separated objects, I do some things with the cube and then I have to select the circle to do some other operations, then when I'm done with that, I want to select the cube to keep working with it, thanks in advance.

see if this helps https://blender.stackexchange.com/questions/44382/blender-python-select-an-object-with-the-sequence-of-letters-in-a-name

That helps to select it, but I want to change the "active" property, so when you go bpy.context.active_object the object is now the second one. In other words I need to convert a secondary selection into the active and the active into the secondary, thanks for the reply nonetheless.

I found the answer here.
The way you make an object active is through the overwrite of:
bpy.context.scene.objects.active

so if you have a Cube named 'Cube', and you want to make it active, you will do:
cube = bpy.data.objects['Cube']
bpy.context.scene.objects.active = cube


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How does blender convert a color's value to a numeric value?
I've been creating procedural materials in cycles likewise creating roughness textures but recently something's been bothering me. The Value showed in the HSV do not match with an actual numeric value, thus creating unexpected results.
In my current scene I have a gray color which has 0.5 as Value in the HSV sliders, but then if I connect that into roughness or any other slot that needs values I get a different result than if I input a value node with 0.5 as value (hopefully this paragraph made sense). So my question here would be, how to treat colored textures (roughness for instance) in order to get the correct output values (or at least the desired ones), meaning that if I have a texture with HSV showing 0.5, the actual value be 0.5.
Thanks in advance :).

A math value of 0.5 is like assigning RGB values of 0.5 each, which is a HSV value of 0.735.
I don't know the logic underneath this choice, I think it's about linear and logarithmic perception of light.

I didn't now RGB was the way to go for values, thanks a lot!


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How to create a custom voronoi diagram with cycles nodes?
I've been looking for a way to create my own Voronoi diagram using cycles nodes, I've seen scripts that do just that but I wanted to create it using just math nodes within the Shader Editor, besides I know nothing about scripting shaders or textures. Anyway, the reason behind this is that I want to have control over the points location, this to recreate the patterns seen on reptile skins, like the example below.

Having control over the points location could allow me to vary the scale, flow and evenness of the scales which is just what I'm looking for.
Also, if someone could show me the way to assign texture coordinates to each cell, so I can put unique textures for each cell, I would highly appreciate it!

I'm open for workarounds but I really want it to be for procedural texturing without doing many manual actions. Thanks in advance

I don't think that can realistically be achieved with procedural approaches. Also giving texture coordinates to each cell won't necessarily enable you to assign unique textures for each.

@DuarteFarrajotaRamos I already solved the texture coordinate point, and it works, it's not as fancy as it sounded. The main problem is still unsolved. I really thought it was possible, since everything at heart is math calculations. Thanks anyway, I'll wait hoping someone can point me in the right direction :)

Speaking about unique textures. You can use image with different textures and then make unique uv-shift for each cell by random or bu positions
Zero position for each:

Then add rule for position-shift.
in this case it is stepped random add (color):

So if your texture contains tiles, that bigger than cells you can fill it.
Also you can choose texture by mix like if cell size is bigger than X, put another texture (or shift UV)


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Dealing with teselated models
So I've been modelling Kylo Ren's lightsaber on solidworks to later make a render in Blender.
The problem is that when I export the model into blender in .stl format it has been teselated, which means that I can´t really apply any modifiers
or smooth shading and makes it look kind of bad.
Using the remesh modifier doesn´t help because its a really complex model.
Do any of you have any advise?
Thanks.

"Do any of you have any advice?" Model it with proper topology  from the start if you plan to use subdivision based techniques and modifiers

Maybe AutoSmooth or EdgeSplit will help for Smooth Shading otherwise read again @DuarteFarrajotaRamos comment.

Modeling a mesh with good topology is an art form in and of itself. I'd recommend modeling inside of Blender with attention to topology from the beginning. Salvaging a bad mesh is extremely difficult and usually harder than making it correctly from nothing.


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Cloth texture not rendering properly when animating
I have created a character, rigged it and added clothes. These clothes are rigged to the armature and the skirt has a cloth modifier added at the end so it moves properly.
The problem is that in the viewport the texture looks fine but when I render the texture is all messed up. This only happens in the frames where the cloth and the rig starts to move. All the textures are mapped form the UV of the skirt. I don´t really know why this only happens on the final render but not in the preview.

It looks like your "Viewport" and "Render" subdivisions are set differently. Depending on how you're rendering, that can make a huge difference at values that low (0-3 really). It may also be affecting baked cloth simulations.
I recommend setting them to the same value. Possibly also bumping it up to 3.


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Missing parts or texture when importing sketch-up model in Blender
Disclaimer: I am everything but a Blender expert.
When I go to https://www.shapenet.org/taxonomy-viewer to the car category and click on a model and click on Source I end up on 3dwarehouse.sketchup website where I can download a collada file (readable by blender).
For instance https://3dwarehouse.sketchup.com/model.html?id=2d096d5dc0e0eeb370a43c2d978e502e shows a 2006 Honda Civic.
After importing it in Blender (File -> Import -> Collada) I end up with different results depending on the model I clicked on:
Either:
-I cannot see anything except the two extreme points
-I can see the body of the car and wheels in two different places
-I can see the body of the car without the tires
-I can see the whole thing normally
In every case whenever I render it I also get black texture artifacts everywhere.
However in shapenet viewer everything is perfectly normal in every case !
How to import it correctly to blender to render it and obtain approximately the same kind of render shapenet displays ?

sounds like z fighting (caused by faces occupying the same exact space) but can't tell just by a description

3D Wahrehouse models and sketchup models are well know for very poor quality, inverted normals and don't generally cooperate well with other applications. Also read https://blender.stackexchange.com/questions/57531/fbx-export-why-there-are-no-materials-or-textures/57541

I will update my question with some concrete examples


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Camera direction and `view_frame()` - How to calculate the direction vectors that describe the corners of the camera frame
The camera origin is:
scene = bpy.data.scenes["Scene"]
camera_origin = scene.camera.location

The camera direction is calculated with
camera_direction = scene.camera.matrix_world.to_quaternion() @ Vector((0.0,0.0,-1.0))

The view_frame i.e. camera_corners are:
camera_corners = scene.camera.data.view_frame(scene=scene)  # camera corners

At this point camera_corners contains 4 vectors.
Question:
From the camera_origin, how do I calculate the direction of the view_frame/camera_corners similar to the camera_direction?

See links I posted in previous question re using these.  The view_frame method gives local coords of camera bounds.  Convert to global just as have with camera -Z axis.