Thanks, I will report it. I’m using CUDA
I’m not sure if volumetrics is still an incomplete feature in new Cycles. Just in case here’s a simple example where render result in 3.0 is noisy than 2.9:
https://pasteall.org/blend/e4532ac77f9e4285b57d93f0e4fa1c20
Not sure if it’s me, but with the latest two releases, switching from view port shading rendered, to solid, causes Blender to close
blender-3.0.0-alpha+master.26dac33ce18f-windows.amd64-release
blender-3.0.0-alpha+master.439c9b0b8478-windows.amd64-release
If it helps, here’s part of the log (I can post the full log if needed)
backtrace
Exception Record:
ExceptionCode : EXCEPTION_ACCESS_VIOLATION
Exception Address : 0x00007FFA9BAA14D3
Exception Module : VCRUNTIME140.dll
Exception Flags : 0x00000000
Exception Parameters : 0x2
Parameters[0] : 0x0000000000000001
Parameters[1] : 0x000001D8AB2D6000
Stack trace:
VCRUNTIME140.dll :0x00007FFA9BAA12F0 memcpy
blender.exe :0x00007FF6358B3EE0 ccl::PathTraceDisplay::copy_pixels_to_texture
blender.exe :0x00007FF6358BCC20 ccl::PathTraceWorkGPU::copy_to_display_naive
blender.exe :0x00007FF6358BC960 ccl::PathTraceWorkGPU::copy_to_display
blender.exe :0x00007FF6358ADD80 ccl::PathTrace::update_display
blender.exe :0x00007FF6358AD170 ccl::PathTrace::render_pipeline
blender.exe :0x00007FF6358AD0B0 ccl::PathTrace::render
blender.exe :0x00007FF635754C60 ccl::Session::run_main_render_loop
blender.exe :0x00007FF635754890 ccl::Session::run
blender.exe :0x00007FF6387591C0 ccl::thread::run
blender.exe :0x00007FF6351A8F90 std::thread::_Invoke<std::tuple<void * __ptr64 (__cdecl*)(void * __ptr64),ccl::thread * __ptr64>,0,
ucrtbase.dll :0x00007FFAA0FC1B20 configthreadlocale
KERNEL32.DLL :0x00007FFAA1867020 BaseThreadInitThunk
ntdll.dll :0x00007FFAA30A2630 RtlUserThreadStart
Hi, I cant verify on Linux with build: October 07, 02:17:56 - master - 439c9b0b8478
I will test on Windows and edit here.
EDIT:
No crash on: 3.0.0 Alpha, branch: master, commit date: 2021-10-04 07:43, hash: 8c55333a8e80, type: release
build date: 2021-10-04, 08:23:56
Maybe you check from CMD with --factory-startup switch.
Cheers, mib
Thanks for checking @mib2berlin
I see you tested the build from October 4th.
The builds until Oct 5 work fine on my end as well, the issue is happening only on the latest two builds that I mentioned above (Oct 6, and 7):
blender-3.0.0-alpha+master.26dac33ce18f-windows.amd64-release
blender-3.0.0-alpha+master.439c9b0b8478-windows.amd64-release
I also tried with the default factory settings, and the issue is still happening.
Yes I see that it is noisier.
The first image is with 2.9 and 3.0. I don’t think it is a bug it may be some differences in the path tracing algorithm. However, it would be good to log is as a bug so that it gets looked into.
1 Like
You should use blender to report this as a bug. That way we get all your details.
Hi, I tested now with
3.0.0 Alpha, branch: master, commit date: 2021-10-06 22:38
hash: 439c9b0b8478, type: release
build date: 2021-10-07, 00:04:42
I render default scene on CPU, GPU, CPU+GPU, Cuda and Optix in the viewport and switch back and forth solid and render.
I5, RTX 2060.
No crash.
You can report it to the bug tracker, maybe a developer can reproduce.
Create info text file from Help menu and past it to the report.
If you start the report from the Help menu Blender fills many information automatically to the report form.
Cheers, mib
I think it’s actually an issue with CPU rendering in 2.93. If you compare cpu and gpu rendering there, cpu is much cleaner. But on 3.0 both devices produce identical results, and noise level is similar to gpu rendering in 2.93. Also it’s more than 2x faster.
Now that you mention this, I think I remember that volumetrics on GPU had some limitations compared to CPU. Even the .blend file of this old report of mine still gives problems with hybrid GPU+CPU render in 2.93 and 3.0 (Black tiles in 2.93 and Black bands in 3.0)
https://developer.blender.org/T52013
and now I see where the node configuration I was using came from
@YAFU and @slowburn
With regard to the volumetric situation and differences between Cycles in Blender 3.0 and 2.93 and GPU vs CPU and such, here’s some information that might be useful:
In Cycles there are two ways to sample a value. “Distance” sampling and “Equiangular” sampling. Cycles by default uses the “Multi-importance” sampling method which means it picks the sampling method that is believed to be the best for the object in this scene.
With Cycles in Blender 2.93 the CPU supported “Distance” and “Equiangular” sampling. The GPU only supported “Distance” sampling. This means you might render a scene in Blender 2.93 on the CPU and it’s relatively noise free at a low sample count due to “Equiangular” sampling. But if you render the same scene with the GPU which only supports “Distance” sampling, it might look noisier at the same sample count. (Note: Neither “Distance” or “Equiangular” sampling is better, they’re better in different situations)
In Blender 3.0 with the Cycles-X merge, both the CPU and GPU support “Distance” and “Equiangular” sampling, so now the difference of CPU vs GPU with different sampling methods shouldn’t be an issue (there still appears to be some small differences though). But, as @YAFU has pointed out, volumetric objects in Cycles with Blender 3.0 does appear to be noiser than 2.93. And it’s not because of the sampling method difference.
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So hybrid GPU+CPU render with that “Volumetric World Texture.blend” file from that old report shouldn’t give problems in 3.0?
Can you reproduce that black bands in 3.0 with GPU+CPU in that file?
(it is the GPU that contributes the black part)
Yes I can.
GPU: RTX 3090
CPU: Ryzen 9 5950X
This should be reported as a bug.
1 Like
Thanks, @leesonw @mib2berlin
Bug submitted: ⚓ T92015 Renders don't work, and viewport bug
For the record, it doesn’t render, but it also quits when switching from shading rendered mode to solid.
1 Like
@YAFU I have made a bug report for the issue you talked about here: ⚓ T92036 Cycles: Certain Volumetric World Shaders render differently with the CPU and GPU
1 Like
ShaderNodeLightPath not work properly.
result of (cycles-x.342cdb03ee06) and (master.a78d3c5261b5)
result of (master.26dac33ce18f) and (master.439c9b0b8478)
Yes please report this, with a sample scene if possible 
A general info: Please report bugs to the bug tracker (Use Help → Report a Bug from within Blender). We cannot keep track of issues reported here.
1 Like
OK, I will report this with a sample scene. And here is another thing, transparent bsdf seems have a fixed refract ior like 1.45 or 1.60 which is much higher than I wanted. Is this possible to reduce this value by using graph/node tree? If not possible, I may change the source code, but I only find blender\kernel\shaders\node_transparent_bsdf.osl.
#include “stdcycles.h”
shader node_transparent_bsdf(color Color = 0.8, normal Normal = N, output closure color BSDF = 0)
{
BSDF = Color * transparent();
}
No idea where transparent() function comes, it is not in stdcycles.h.