Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using hidden CPU Branched Path Tracing samples and not the Path Tracing samples #84872

New Issue

Michael Klein · 2021-01-19T23:04:55+01:00

Michael Klein commented

2021-01-19 23:04:55 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2070 Super/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.89

Blender Version
Broken: version: 2.92 Beta, 2.93.0 Alpha, branch: master, commit date: 2021-01-18 23:28, hash: 09c7c63890
Worked: n.a.

Short description of error
Adaptive Sampling with GPU+CPU is using the hidden CPU Branched Path Tracing samples and not the samples set in GPU mode. I found this bug by random because I wondered why hybrid rendering takes so long and looks good with 128 samples while GPU only was fast and noisy as expected. The reason was that CPU sampling was set to BPT and 4.096 before I switched the device from CUDA to OptiX and GPU will not support BPT in this case. Rendering will not use the visible 128 samples but the hidden 4.096 samples.

Exact steps for others to reproduce the error

Set Preferences>System>Cycles Render Device to OptiX
Select CPU device
Set to BPT
Set high samples eg. 4.096
Select GPU device
Set low samples 128
Disable CPU in Preferences>System
Render in GPU mode: Result is fast and noisy
Enable CPU in Preferences>System
Render in GPU mode: Result is slow and less noisy

Reason: The hidden CPU BPT samples of 4.096 will be used here and not the GPU PT samples of 128.

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce RTX 2070 Super/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.89 **Blender Version** Broken: version: 2.92 Beta, 2.93.0 Alpha, branch: master, commit date: 2021-01-18 23:28, hash: `09c7c63890` Worked: n.a. **Short description of error** Adaptive Sampling with GPU+CPU is using the hidden CPU Branched Path Tracing samples and not the samples set in GPU mode. I found this bug by random because I wondered why hybrid rendering takes so long and looks good with 128 samples while GPU only was fast and noisy as expected. The reason was that CPU sampling was set to BPT and 4.096 before I switched the device from CUDA to OptiX and GPU will not support BPT in this case. Rendering will not use the visible 128 samples but the hidden 4.096 samples. **Exact steps for others to reproduce the error** - Set Preferences>System>Cycles Render Device to OptiX - Select CPU device - Set to BPT - Set high samples eg. 4.096 - Select GPU device - Set low samples 128 - Disable CPU in Preferences>System - Render in GPU mode: Result is fast and noisy - Enable CPU in Preferences>System - Render in GPU mode: Result is slow and less noisy Reason: The hidden CPU BPT samples of 4.096 will be used here and not the GPU PT samples of 128.

Michael Klein commented

2021-01-19 23:04:55 +01:00

Added subscriber: @Renderbicks

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Extreme different behaviour between GPU or GPU+CPU (because CPU sampling is used)~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU is using hidden CPU sample rate and not the actual one

2021-01-19 23:14:45 +01:00

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU is using hidden CPU sample rate and not the actual one~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU is using CPU sample rate when set to Branched Path Tracing

2021-01-19 23:20:47 +01:00

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU is using CPU sample rate when set to Branched Path Tracing~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using CPU sample rate when set to Branched Path Tracing

2021-01-19 23:24:44 +01:00

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using CPU sample rate when set to Branched Path Tracing~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using CPU Branched Path Tracing sample rate and not the Path Tracing samples

2021-01-19 23:28:52 +01:00

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using CPU Branched Path Tracing sample rate and not the Path Tracing samples~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using hidden CPU Branched Path Tracing sample rate and not the Path Tracing samples

2021-01-19 23:31:37 +01:00

Michael Klein changed title from ~~Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using hidden CPU Branched Path Tracing sample rate and not the Path Tracing samples~~ to Blender 2.92/2.93 Adaptive Sampling: Hybrid GPU+CPU (OptiX/RTX) is using hidden CPU Branched Path Tracing samples and not the Path Tracing samples

2021-01-19 23:31:56 +01:00

Alaska commented

2021-01-20 04:02:27 +01:00

Added subscribers: @pmoursnv, @Alaska

Alaska commented

2021-01-20 04:02:27 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Alaska commented

2021-01-20 04:02:27 +01:00

Can confirm.

CC @pmoursnv as I believe you're the most intimate with the code affecting this area.

System Information
Operating system: Linux-5.10.0-1-amd64-x86_64-with-debian-bullseye 64 Bits
Graphics card: GeForce RTX 2060 SUPER 460.27.04

Blender Version
Broken version: 2.93.0 Alpha, branch: master, commit date: 2021-01-19 22:43, hash: 6290091bac

Can confirm. CC @pmoursnv as I believe you're the most intimate with the code affecting this area. **System Information** Operating system: Linux-5.10.0-1-amd64-x86_64-with-debian-bullseye 64 Bits Graphics card: GeForce RTX 2060 SUPER 460.27.04 **Blender Version** Broken version: 2.93.0 Alpha, branch: master, commit date: 2021-01-19 22:43, hash: `6290091bac`

blender-admin commented

2021-01-20 13:03:09 +01:00

This issue was referenced by 10d2cbfa36

This issue was referenced by 10d2cbfa369a512730a53192ccfe2473c9d96035

Patrick Mours self-assigned this 2021-01-20 13:34:30 +01:00

Brecht Van Lommel commented

2021-01-20 15:00:37 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Brecht Van Lommel closed this issue

2021-01-20 15:00:37 +01:00

Michael Klein commented

2021-01-20 22:45:43 +01:00