Different Render Results Between CPU and GPU #89351

New Issue

Rick · 2021-06-22T06:47:42+02:00

Rick commented

2021-06-22 06:47:42 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.77

Blender Version
Broken: version: 2.93.0, branch: master, commit date: 2021-06-02 11:21, hash: 84da05a8b8
Worked: (newest version of Blender that worked as expected)

Short description of error
I've noticed when rendering an ocean scene in cycles, using optix with 1 GPU and a CPU, I get little discolored squares all around the visible portions of the ocean, and the only way to prevent that from happening is to render on either my CPU or GPU alone, switch to a different render device, or just make sure that the ocean isn't visible in the render. Upon writing out this letter, I've also noticed that Optix seems to produce an odd shadow across the object that Cuda does not produce. This shadow also vanishes when rendered in Optix with only my CPU. My graphics card drivers are up to date, and I also tried restarting my PC, but it didn't change anything. I can render with CUDA instead, it's not a problem, but figured I should report the bug anyway.

Exact steps for others to reproduce the error
Render the attached .blend file, with optix as the selected render device, using a single GPU and CPU.Bug Sample blend file.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.77 **Blender Version** Broken: version: 2.93.0, branch: master, commit date: 2021-06-02 11:21, hash: `84da05a8b8` Worked: (newest version of Blender that worked as expected) **Short description of error** I've noticed when rendering an ocean scene in cycles, using optix with 1 GPU and a CPU, I get little discolored squares all around the visible portions of the ocean, and the only way to prevent that from happening is to render on either my CPU or GPU alone, switch to a different render device, or just make sure that the ocean isn't visible in the render. Upon writing out this letter, I've also noticed that Optix seems to produce an odd shadow across the object that Cuda does not produce. This shadow also vanishes when rendered in Optix with only my CPU. My graphics card drivers are up to date, and I also tried restarting my PC, but it didn't change anything. I can render with CUDA instead, it's not a problem, but figured I should report the bug anyway. **Exact steps for others to reproduce the error** Render the attached .blend file, with optix as the selected render device, using a single GPU and CPU.[Bug Sample blend file.blend](https://archive.blender.org/developer/F10187380/Bug_Sample_blend_file.blend) ![Optix CPU and GPU.png](https://archive.blender.org/developer/F10187423/Optix_CPU_and_GPU.png) ![Cuda CPU and GPU.png](https://archive.blender.org/developer/F10187424/Cuda_CPU_and_GPU.png) ![Optix CPU only.png](https://archive.blender.org/developer/F10187425/Optix_CPU_only.png) ![Optix GPU only.png](https://archive.blender.org/developer/F10187426/Optix_GPU_only.png)

Rick commented

2021-06-22 06:47:42 +02:00

Added subscriber: @Arcomade

blender-admin commented

2021-06-22 06:47:42 +02:00

#91570 was marked as duplicate of this issue

Kévin Dietrich commented

2021-06-22 08:04:59 +02:00

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

Leon Zandman commented

2021-06-22 15:00:43 +02:00

Added subscriber: @Zandman

Leon Zandman commented

2021-06-22 15:00:43 +02:00

Isn't it perfectly normal to get different results between rendering on CPU and GPU? They use different algorithms. In general GPU is faster, but CPU supports more rendering features and produces better results. I think I read somewhere that when you want consistent rendering results, you have to either render on GPU or CPU, but not mix both.

Now, there could definitely still be a bug here. Just wanted to add my two cents.

Isn't it perfectly normal to get different results between rendering on CPU and GPU? They use different algorithms. In general GPU is faster, but CPU supports more rendering features and produces better results. I think I read somewhere that when you want consistent rendering results, you have to either render on GPU or CPU, but not mix both. Now, there could definitely still be a bug here. Just wanted to add my two cents.

Aaron Carlisle commented

2021-06-23 01:28:56 +02:00

Added subscriber: @Blendify

Aaron Carlisle commented

2021-06-23 01:28:56 +02:00

@Zandman CPU and GPU should give the same results.

Leon Zandman commented

2021-06-23 01:55:08 +02:00

In #89351#1181105, @Blendify wrote:
@Zandman CPU and GPU should give the same results.

Google says otherwise:

But since this isn’t a discussion forum and it’s not my expertise, I don’t have anything more to add here :-)

> In #89351#1181105, @Blendify wrote: > @Zandman CPU and GPU should give the same results. Google says otherwise: * https://www.reddit.com/r/Amd/comments/65h4py/eli5_why_is_gpu_rendering_lower_quality_than_cpu/ * https://renderpool.net/blog/cpu-vs-gpu-rendering/ * https://blog.cherryservers.com/cpu-or-gpu-rendering-which-is-better-one But since this isn’t a discussion forum and it’s not my expertise, I don’t have anything more to add here :-)

Kévin Dietrich commented

2021-06-25 14:19:24 +02:00

Closed as duplicate of #85078

Kévin Dietrich closed this issue

2021-06-25 14:19:24 +02:00

Leon Zandman commented

2021-06-25 14:23:31 +02:00

What makes you think this is a duplicate of #85078? This issue is about mixing CPU and GPU, right. The other one is just using one variant.

Alaska commented

2021-09-18 08:48:34 +02:00

Added subscriber: @Alaska

Alaska commented

2021-09-18 08:48:34 +02:00

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

Alaska reopened this issue

2021-09-18 08:48:34 +02:00

Alaska commented

2021-09-18 08:48:34 +02:00

In #89351#1182663, @Zandman wrote:
What makes you think this is a duplicate of #85078? This issue is about mixing CPU and GPU, right. The other one is just using one variant.

The reason why these reports were probably merged is because the report is talking about a issue with the GPU rendering differently from the CPU. In this specific case, that OptiX is rendering differently from the CPU.
#85078 (OptiX GPU rendering artifacts with large plane) is a bug report for the issue that's causing OptiX to render differently from the CPU in this case. So once #85078 (OptiX GPU rendering artifacts with large plane) is fixed then this specific bug report will also be fixed.

> In #89351#1182663, @Zandman wrote: > What makes you think this is a duplicate of #85078? This issue is about mixing CPU and GPU, right. The other one is just using one variant. The reason why these reports were probably merged is because the report is talking about a issue with the GPU rendering differently from the CPU. In this specific case, that OptiX is rendering differently from the CPU. #85078 (OptiX GPU rendering artifacts with large plane) is a bug report for the issue that's causing OptiX to render differently from the CPU in this case. So once #85078 (OptiX GPU rendering artifacts with large plane) is fixed then this specific bug report will also be fixed.

Brecht Van Lommel commented

2021-09-22 18:58:52 +02:00

Closed as duplicate of #85078

Brecht Van Lommel closed this issue

2021-09-22 18:58:52 +02:00

Brecht Van Lommel commented

2021-09-22 18:59:35 +02:00

Added subscriber: @brecht