Sheen doesn't render on perpendicular faces in orthographic view. #115206

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opened 2023-11-20 19:26:29 +01:00 by rosen genkov · 4 comments

rosen genkov commented

2023-11-20 19:26:29 +01:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.01

Blender Version
Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08

Short description of error
Sheen (in principle and sheen BSDF) renders as black, when the face is perpendicular to the camera or view.
Cycles render. Ortographic view (or camera). Shade flat object.

Exact steps for others to reproduce the error
Render Engine Cycles
Device GPU compute
Assign a Sheen BSDF shader (or sheen weight in Principle BSDF) to the default cube.
Go to top orthographic view in render mode.
The cube has to be shade flat.
When remesh modifier is used, perpendicular faces are black even in shade smooth mode.
When Subdivision Surface modifier is used in Simple mode, there are also some black faces.

If CPU is used as a device the problem is less prominent. The faces are not black. Just a bit darker than the others.

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.01 **Blender Version** Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` **Short description of error** Sheen (in principle and sheen BSDF) renders as black, when the face is perpendicular to the camera or view. Cycles render. Ortographic view (or camera). Shade flat object. **Exact steps for others to reproduce the error** Render Engine Cycles Device GPU compute Assign a Sheen BSDF shader (or sheen weight in Principle BSDF) to the default cube. Go to top orthographic view in render mode. The cube has to be shade flat. When remesh modifier is used, perpendicular faces are black even in shade smooth mode. When Subdivision Surface modifier is used in Simple mode, there are also some black faces. If CPU is used as a device the problem is less prominent. The faces are not black. Just a bit darker than the others. ![image](/attachments/f895a350-40ae-4a08-a790-2fe82cf4a2d2)

Sheen Shading Issue.blend

975 KiB

1.3 MiB

1.3 MiB

rosen genkov added the

labels 2023-11-20 19:26:29 +01:00

Iliya Katushenock added the

Render & Cycles

label 2023-11-20 19:33:41 +01:00

Ian Failing commented

2023-11-20 20:08:24 +01:00

I reproduced a similar effect; it seems undesired. Steps:

Default cube
Orthographic projection
Top orthographic view
View Rendered
Render Cycles
Cube material = Sheen BSDF
Light Power = 10000
Mouse3-drag 1 pixel
Sharp discontinuity of response from black to mid-gray

System Information
Operating system: Windows-10-10.0.23590-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.09

Blender Version
Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08
Broken: version: 4.1.0 Alpha, branch: main, commit date: 2023-11-18 21:46, hash: 9eba3902c904

I reproduced a similar effect; it seems undesired. Steps: 1. Default cube 2. Orthographic projection 3. Top orthographic view 4. View Rendered 5. Render Cycles 6. Cube material = Sheen BSDF 7. Light Power = 10000 8. Mouse3-drag 1 pixel 9. Sharp discontinuity of response from black to mid-gray **System Information** Operating system: Windows-10-10.0.23590-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.09 **Blender Version** Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` Broken: version: 4.1.0 Alpha, branch: main, commit date: 2023-11-18 21:46, hash: `9eba3902c904`

Pratik Borhade commented

2023-11-21 07:07:44 +01:00

Member

Hi, thanks for the report. Can confirm. Recent refactor and new layer structure have caused the bug.
Behavior changed between fca8df9415b1 - 264c3e7bd7a6

Hi, thanks for the report. Can confirm. Recent refactor and new layer structure have caused the bug. Behavior changed between `fca8df9415b1 - 264c3e7bd7a6`

Pratik Borhade added

Render & Cycles

and removed

Render & Cycles

labels 2023-11-21 07:08:04 +01:00

Brecht Van Lommel commented

2023-11-21 14:38:02 +01:00

Owner

@LukasStockner, can you check?

@LukasStockner, can you check?

Alaska commented

2023-11-22 12:30:51 +01:00

Member

A quick comment for @brecht and/or @LukasStockner or anyone else if they want to look into this.

The issue is caused by make_orthonormals_tangent() as called by bsdf_sheen_setup() in /intern/cycles/kernel/closure/bsdf_sheen.h.

What's happening is two parallel vectors are being passed to make_orthonormals_tangent() (these vectors are bsdf->N and sd->wi).

make_orthonormals_tangent() then does some math (normalize(cross(bsdf->N, sd->wi))) which produces NaNs which cause issues later one. This is because the cross product of identical vectors are 0, and a normalized 0 vector is NaN.

Swapping normalize out for safe_normalize fixes a assert caused by the NaNs and fixes the black rendering issue, but now there's discontinuities in some areas since the vector is 0, 0, 0 in one region and 0.7, 0.7, 0.0 right beside it. Just for reference, this discontinuity can be seen in the test scenes on the two cubes that partially render correctly.

I'm not sure what the desired result would be for this case (bsdf->N == sd->wi) so I don't know how to fix it. But hopefully the informaiton helps.

A quick comment for @brecht and/or @LukasStockner or anyone else if they want to look into this. The issue is caused by `make_orthonormals_tangent()` as called by `bsdf_sheen_setup()` in `/intern/cycles/kernel/closure/bsdf_sheen.h`. What's happening is two parallel vectors are being passed to `make_orthonormals_tangent()` (these vectors are `bsdf->N` and `sd->wi`). `make_orthonormals_tangent()` then does some math (`normalize(cross(bsdf->N, sd->wi))`) which produces NaNs which cause issues later one. This is because the cross product of identical vectors are 0, and a normalized 0 vector is NaN. Swapping `normalize` out for `safe_normalize` fixes a assert caused by the NaNs and fixes the black rendering issue, but now there's discontinuities in some areas since the vector is `0, 0, 0` in one region and `0.7, 0.7, 0.0` right beside it. Just for reference, this discontinuity can be seen in the test scenes on the two cubes that partially render correctly. I'm not sure what the desired result would be for this case (`bsdf->N == sd->wi`) so I don't know how to fix it. But hopefully the informaiton helps.

Alaska referenced a pull request that will close this issue

2023-11-23 04:14:36 +01:00

Fix #115206: Sheen renders incorrectly in certain situations #115286

Brecht Van Lommel referenced this issue from a commit

2023-11-27 11:34:11 +01:00

Fix #115206: Sheen renders incorrectly when viewed head on

Brecht Van Lommel closed this issue

2023-11-27 11:34:12 +01:00

Blender Bot added

and removed

labels 2023-11-27 11:34:14 +01:00

Brecht Van Lommel referenced this issue

2023-11-27 11:35:49 +01:00

4.0: Candidates for corrective releases #114706

Thomas Dinges referenced this issue from a commit

2023-12-01 11:44:55 +01:00

Fix #115206: Sheen renders incorrectly when viewed head on

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