UsdPreviewSurface does not respect normals texture bias and scale #106326

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Eric-Haines · 2023-03-30T18:36:35+02:00

Eric-Haines commented

2023-03-30 18:36:35 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 528.02

Blender Version
Broken: version: 3.6.0 Alpha, branch: cycles-light-linking, commit date: 2023-03-30 09:25, hash: 741a5bc734d2
Worked: (newest version of Blender that worked as expected)

Short description of error
The UsdPreviewSurface material includes a bias and scale value to modify normal textures. Blender's USD importer does not interpret these input values, leading to rendering errors.

Exact steps for others to reproduce the error
I have put the Blender files needed as attached files. I will also explain below how to load the NormalsTextureBiasAndScale.usda in Blender and set up the test conditions, in case there is a problem with my .blend save file.

The normal texture bias and scale values and their importance is explained in depth on the USD Assets repository site on this page.

Short version: load normal_bias_and_scale.blend and compare results - see end of this report. The images differ because normal texture map bias and scale are not interpreted by the USD importer.

Long version, importing the original USD test file: Download the NormalsTextureBiasAndScale.usda model and PNG textures attached below, or there.
Start Blender.
Delete the default Cube and Light objects.
Import NormalsTextureBiasAndScale.usda into Blender: File -> Import -> USD
Select Camera.001 and make it active (select it, then in upper left: View -> Cameras -> Set Active Object as Camera).
Select Viewport Shading (icon in upper right of viewport). Eevee renderer is assumed.
Open the NormalsTextureBiasAndScale model in the Scene Collection (upper right of screen).
Select the AngledLight.
In the lower right, pick the Object Data Properties and change the Strength from 50000 to 4.8, which will match the repo's image fairly well. (It being 50000 by default is a separate bug.)

In Blender three "R" bump maps appear on each cube:

(Attached, also at https://i.postimg.cc/j2cgh6n9/blender-normals.jpg)

These "R" images should all look about the same along the three tops. They do not in Blender, but do in usdview, for example. Here's the usdview render, from the repo page:

Similarly, the three left sides should be about the same, and three right sides should be about the same.

The problem is simply missing functionality: the normals scale and bias values in UsdPreviewSurface are not interpreted. These are important to interpret properly, as DirectX and OpenGL typically expect different types of normal maps, for example.

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 528.02 **Blender Version** Broken: version: 3.6.0 Alpha, branch: cycles-light-linking, commit date: 2023-03-30 09:25, hash: `741a5bc734d2` Worked: (newest version of Blender that worked as expected) **Short description of error** The UsdPreviewSurface material includes a bias and scale value to modify normal textures. Blender's USD importer does not interpret these input values, leading to rendering errors. **Exact steps for others to reproduce the error** I have put the Blender files needed as attached files. I will also explain below how to load the NormalsTextureBiasAndScale.usda in Blender and set up the test conditions, in case there is a problem with my .blend save file. The normal texture bias and scale values and their importance is explained in depth on the [USD Assets repository site on this page](https://github.com/usd-wg/assets/tree/main/test_assets/NormalsTextureBiasAndScale). Short version: load normal_bias_and_scale.blend and compare results - see end of this report. The images differ because normal texture map bias and scale are not interpreted by the USD importer. Long version, importing the original USD test file: Download the NormalsTextureBiasAndScale.usda model and PNG textures attached below, or [there](https://github.com/usd-wg/assets/tree/main/test_assets/NormalsTextureBiasAndScale). Start Blender. Delete the default Cube and Light objects. Import NormalsTextureBiasAndScale.usda into Blender: File -> Import -> USD Select Camera.001 and make it active (select it, then in upper left: View -> Cameras -> Set Active Object as Camera). Select Viewport Shading (icon in upper right of viewport). Eevee renderer is assumed. Open the NormalsTextureBiasAndScale model in the Scene Collection (upper right of screen). Select the AngledLight. In the lower right, pick the Object Data Properties and change the Strength from 50000 to 4.8, which will match the repo's image fairly well. (It being 50000 by default is a separate bug.) In Blender three "R" bump maps appear on each cube: ![AngledLight adjusted view](https://erich.realtimerendering.com/download/blender/blender_normals.jpg) (Attached, also at https://i.postimg.cc/j2cgh6n9/blender-normals.jpg) These "R" images should all look about the same along the three tops. They do not in Blender, but do in usdview, for example. Here's the usdview render, from the repo page: ![USD Assets view](https://github.com/usd-wg/assets/raw/main/test_assets/NormalsTextureBiasAndScale/screenshots/crn_usdview.png) Similarly, the three left sides should be about the same, and three right sides should be about the same. The problem is simply missing functionality: the normals scale and bias values in UsdPreviewSurface are not interpreted. These are important to interpret properly, as DirectX and OpenGL typically expect different types of normal maps, for example.

r_normal_map_reversed_x_0_bias_z.png

35 KiB

NormalsTextureBiasAndScale.usda

12 KiB

r_normal_map.png

33 KiB

r_normal_map_reversed_y.png

33 KiB

blender_normals.jpg

151 KiB

normal_bias_and_scale.blend

976 KiB

Eric-Haines added the

labels 2023-03-30 18:36:36 +02:00

Pratik Borhade commented

2023-03-31 08:58:16 +02:00

Hi, thanks for the report. I can confirm the difference in textures of each cube.
If I understand correctly, bias and scale are used to match the "Normal texture" range [-1, 1].
Maybe issue is that the "scale" and "bias" attributes are not found during the import and their default values are used i.e. float4 2.0 and float4 -1.0 resp.
My findings might be wrong.
cc @makowalski

Hi, thanks for the report. I can confirm the difference in textures of each cube. If I understand correctly, bias and scale are used to match the "Normal texture" range [-1, 1]. Maybe issue is that the "scale" and "bias" attributes are not found during the import and their default values are used i.e. float4 2.0 and float4 -1.0 resp. My findings might be wrong. cc @makowalski

👍 1

Pratik Borhade added

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UsdPreviewSurface does not respect normals texture bias and scale #106326