Cycles brightness difference between CPU, GPU and CPU+GPU #101816
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Reference: blender/blender#101816
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System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.59
Blender Version
Broken: version: 3.3.1, branch: master, commit date: 2022-10-04 18:35, hash:
b292cfe5a9Short description of error
Seems a noticeable difference on how cycles render depending if you use GPU, CPU and XPU and you use transparent materials.
GPU
CPU:
CPU+GPU:
As you can see, there's a visible line at the top of the render-
Trying to encapsulate the bug i get this result.
Create a interior scene, add a glass material and try to render with both CPU and GPU.
**i guess the problem is related to the material.
Here is the scene..
GlobalIllumination2.blend
Thanks.
Added subscriber: @Musikdoktor
Added subscriber: @OmarEmaraDev
What does XPU mean here? CPU + GPU?
Yes.
That difference on "brightness" creates the line at the top.. i think is a difference on how it calculates how many light pass through a transparent material. and i think the problem is in de GPU side of the code.
Changed status from 'Needs Triage' to: 'Confirmed'
Cycles brightness difference between CPU, GPU and XPUto Cycles brightness difference between CPU, GPU and CPU+GPUAdded subscriber: @LukasStockner
I can't reproduce any issue in the attached scene, neither in 3.3.1 nor in the current master. CPU, CUDA, OPTIX and CPU+CUDA all give an identical render.
Tested on Linux with an RTX 3090, driver version 515.76 and CUDA 11.8.
Added subscriber: @Fernando-Alcala
Reproducable on Windows 10 on GPU.
The problem is with respect to the Principled BSDF.
If the Alpha is greater than 0 and less than the Transmission, then the scene becomes darker.
Alpha .001 and Transmission 1
Setting the Alpha to the default of 0 is better but still incorrect.
Setting the Alpha to 1 produces the same image as the...
Reference image with CPU and glass BSDF
Thanks for testing guys.
Btw, im using Windows 11 not 10..
Here is another example of issue.
Principled v2 seems to have fixed the gross inaccuracy, but there is still a slight difference in color.
GPU
CPU
Again, setting both transmission and alpha to 1 creates an exact render as a glass BSDF.