Textures mapped on UVs with very high location values appear emissive when rendering on CPU #99795

New Issue

Karl · 2022-07-17T16:20:51+02:00

Karl commented

2022-07-17 16:20:51 +02:00

Textures mapped on UVs that have vertices with very high location values appear emissive or black with CPU rendering. The UV vertex location values are around the range -3960966.

Original Report

System Information
Operating system: macOS Monterey 12.4
Graphics card: Apple M1 Max

Blender Version
Broken: In every version I can find but for example in 3.2.1 2022-07-06 and 2.80 2019-07-29 as well as the nightly alpha 3.3.0 2022-07-17
Worked: Cannot find a version in which it works.
system-info.txt

Background

I'm generating images in python using a script and I load objects from a dataset called SceneNet. Some of these objects have poor UV mapping, which is not a big deal, but it's causing rendering artifacts which are a problem.

The Bug

When a surface has incorrect UV mapping and has a stretched out texture, it leads to the surface becoming extremely bright. It does not emit light, the issue only occurs when there is a light source, emissive surface, or world background in the scene. The surfaces with stretched textures seem to multiply the reflected light by a high factor.

In the viewport the issue only occurs when rendering on CPU. When rendering on GPU, the texture looks stretched out but with the correct color and not bright.
Example 1:
GPU ONLY CPU
Example 2:
GPU ONLY CPU
Example 3, the same scene but with UV mapping fixed for part of the wall:
CPU
Example 4, blender 3.3.0 2022-07-17:
GPU CPU Replaced problem faces with 100% white diffuse material

When rendering to file, I have seen two cases:

The image looks like in the viewport while rendering, but when finishing the render the image becomes black.
When rendering with mixed CPU+GPU in Blender 3.1.0, the upper part of the image has the lighting issue from the CPU, and the rest of the image looks fine.

Desired behavior:
The result from pure GPU rendering is the desired behavior.

Exact steps for others to reproduce the error
Open attached .blend file, change viewport to render, switch between GPU and CPU rendering to see the difference. Try render to file using CPU/GPU/Mixed.
bug-textures.blend

Textures mapped on UVs that have vertices with very high location values appear emissive or black with CPU rendering. The UV vertex location values are around the range -3960966. ### Original Report **System Information** Operating system: macOS Monterey 12.4 Graphics card: Apple M1 Max **Blender Version** Broken: In every version I can find but for example in 3.2.1 2022-07-06 and 2.80 2019-07-29 as well as the nightly alpha 3.3.0 2022-07-17 Worked: Cannot find a version in which it works. [system-info.txt](https://archive.blender.org/developer/F13297201/system-info.txt) **Background** I'm generating images in python using a script and I load objects from a dataset called SceneNet. Some of these objects have poor UV mapping, which is not a big deal, but it's causing rendering artifacts which are a problem. **The Bug** When a surface has incorrect UV mapping and has a stretched out texture, it leads to the surface becoming extremely bright. It does not *emit* light, the issue only occurs when there is a light source, emissive surface, or world background in the scene. The surfaces with stretched textures seem to multiply the reflected light by a high factor. **In the viewport** the issue only occurs when rendering on CPU. When rendering on GPU, the texture looks stretched out but with the correct color and not bright. Example 1: GPU ONLY ![ex1-gpu.png](https://archive.blender.org/developer/F13297203/ex1-gpu.png) CPU ![ex1-cpu.png](https://archive.blender.org/developer/F13297202/ex1-cpu.png) Example 2: GPU ONLY ![ex2-gpu.png](https://archive.blender.org/developer/F13297206/ex2-gpu.png) CPU ![ex2-cpu.png](https://archive.blender.org/developer/F13297205/ex2-cpu.png) Example 3, the same scene but with UV mapping fixed for part of the wall: CPU ![ex3-fixed-partially.png](https://archive.blender.org/developer/F13297204/ex3-fixed-partially.png) Example 4, blender 3.3.0 2022-07-17: GPU ![original-gpu.png](https://archive.blender.org/developer/F13297289/original-gpu.png) CPU ![original.png](https://archive.blender.org/developer/F13297287/original.png) Replaced problem faces with 100% white diffuse material ![white.png](https://archive.blender.org/developer/F13297291/white.png) **When rendering to file**, I have seen two cases: - The image looks like in the viewport while rendering, but when finishing the render the image becomes black. - When rendering with mixed CPU+GPU in Blender 3.1.0, the upper part of the image has the lighting issue from the CPU, and the rest of the image looks fine. ![ex4.jpg](https://archive.blender.org/developer/F13297218/ex4.jpg) **Desired behavior:** The result from pure GPU rendering is the desired behavior. **Exact steps for others to reproduce the error** Open attached .blend file, change viewport to render, switch between GPU and CPU rendering to see the difference. Try render to file using CPU/GPU/Mixed. [bug-textures.blend](https://archive.blender.org/developer/F13297275/bug-textures.blend)

Karl commented

2022-07-17 16:20:51 +02:00

Added subscriber: @karl_12345

Karl commented

2022-07-17 16:35:32 +02:00

Additionally, in the Blender render window the problematic faces look darker than in the renders

Additionally, in the Blender render window the problematic faces look darker than in the renders ![interface.png](https://archive.blender.org/developer/F13297305/interface.png)

Omar Emara commented

2022-07-17 19:39:04 +02:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-07-17 19:39:04 +02:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Omar Emara commented

2022-07-17 19:39:04 +02:00

I can confirm that, but this could be a known limitation, because UVs have very high values, in the range around -3960966, so they could be prone to limited precision computations. So tagging the module for more information.

Omar Emara changed title from ~~Incorrectly mapped textures reflects light incorrectly only when rendering on CPU~~ to Textures mapped on UVs with very high location values appear emissive when rendering on CPU

2022-07-17 19:41:57 +02:00

Philipp Oeser removed the

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Textures mapped on UVs with very high location values appear emissive when rendering on CPU #99795

Original Report