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Blender cycles volumetric rendering bug
Closed, ResolvedPublic

Description

System Information
Windows 8 GTX 760

Blender Version
Broken: 2.78/2.79

Short description of error
Blender cycles showing artifacts of volumetric shaders when objects are in front of each other before the camera.

Exact steps for others to reproduce the error
In order to reproduce the effect, just open the blend file and hit render or preview render in order to see the concerning artifacts during rendering.

Thanks in advance,

Kind regards,

Event Timeline

LazyDodo (LazyDodo) triaged this task as Confirmed, Medium priority.

thought this might be fixed due to recent work in this area, but can still reproduce with latest master

Hello LazyDodo,

Thank you for your quick view on this. If i may ask, what would be your prognosis for this bug to be solved?
I am asking since i am working on a project and this bug is disabling me to continue.

Thanks again.

Kind regards,

I only do the initial triaging, someone from the cycles team will have to take a closer look at this point.

Ok thanks LazyDodo, I will just wait and see what happens

Here Linux, just making observations. In Blender 2.79 official release I can see the black hole and a lot of noise around it. Increasing light paths > Max Transparency to 16 the black hole improves a bit, still a lot of noise around.

From master/buildbot the black hole does not appear in scene. But that area with strange strong noise still needs very many samples to improve compared to the rest.

Hi there,

I can also confirm the bug on Linux Mint 18.3. Very strange. The only setting that kind of changes anything is the "Step Size" of the volume sampling.
I know how it feels like to hit a brickwall during a project. If you can live with ~3 times the rendering time but get a result you might be able to live with, you can change the step size from the default 0.1 to something smaller like 0.01.
Here's the result:

I know it's not the final solution, but it might be enough to get the job done.

I need to look into it in detail, but reducing the step size may end up being the correct solution.

If the step size is significantly bigger than the features in the volume, most samples will miss those features. Things get worse if you have many such features behind each other, as is the case here.

It seems this is not possible for me because i have to render other renderlayers, i will however increase sample and crank up the denoiser for that layer, which seem to work ok for the scene. Thanks for your help and i hope that the noise issue could be solved in the future.

Thanks again.

Kind regards,

Fixed now in master, there was a bug.

BeforeAfter

Render looks great and using only 47 samples. Thanks Brecht.
It seems that Roger will be able to save a lot of render time using default value of step size.
Unfortunately it seems that Buildbot is having problems to build Windows versions.

Wow thanks you guys for all the effort. Unfortunately i only have windows :(
Well I hope that maybe the windows version can be build as well.

actually even the overall render looks better even for the singular blobs.

Many thanks :)

Best regards,

Wow you guys, you actually did it. looking at a perfect 50 samples render of the concerning bug file. You guys are awesome. Actually this stuff is for a blender course i am making. Be sure that i will talk about the awesome work and support you all are giving to the blender community.

You guys have my graditude and support :)

All the best