Cycles All Transmission Render Passes wrong over bright image data with GlassBSDF #108211

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Eric Klein · 2023-05-24T01:20:27+02:00

Eric Klein commented

2023-05-24 01:20:27 +02:00

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 522.30

Blender Version
Broken: 4.0, 3.6 beta, 3.6 175b1b449ec2
Worked: Daily build from 3.6.0 Alpha from March 5 - 2023

Short description of error
Cycles all the transmission passes (Direct, Indirect and Color) have wrond over bright image data when using GlassBSDF. Replacing the GlassBSDF with PrincipleBSDF solves image artifacts.

Checking the commit history. It looks like the commits from Lukas Stockner on 3-25-2023. The "Cycles: Use per-microfacet Fresnel term for Glass closures" or "Cycles: Make Fresnel term independent of microfacet closure type" broke the transmission render passes.

Exact steps for others to reproduce the error

Load demo BMW blender scene or attached file.
Enable Cycles render preview.
Select the "Transmission Direct" render pass.
Compare with release 3.5 for reference.

See images below the over bright from blender 3.6 March 6 forward compared to March 5 build.

3.5	3.6

Test file:
Material_GlassBSDF.blend

**System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 522.30 **Blender Version** Broken: 4.0, 3.6 beta, 3.6 `175b1b449ec2` Worked: Daily build from 3.6.0 Alpha from March 5 - 2023 **Short description of error** Cycles all the transmission passes (Direct, Indirect and Color) have wrond over bright image data when using GlassBSDF. Replacing the GlassBSDF with PrincipleBSDF solves image artifacts. Checking the commit history. It looks like the commits from Lukas Stockner on 3-25-2023. The "Cycles: Use per-microfacet Fresnel term for Glass closures" or "Cycles: Make Fresnel term independent of microfacet closure type" broke the transmission render passes. **Exact steps for others to reproduce the error** 1. Load demo BMW blender scene or attached file. 2. Enable Cycles render preview. 3. Select the "Transmission Direct" render pass. 4. Compare with release 3.5 for reference. See images below the over bright from blender 3.6 March 6 forward compared to March 5 build. | 3.5 | 3.6 | | -------- | -------- | | ![Image](https://projects.blender.org/blender/blender/attachments/0bb807d3-139b-4211-b227-450a1465ef4c) | ![Image](https://projects.blender.org/blender/blender/attachments/0dd22b28-971e-4cfa-9a1a-e3e071b45f7c) | | ![image](https://projects.blender.org/attachments/e75f7b86-62ac-4b16-8f80-40cf94cb0030) | ![Image](https://projects.blender.org/attachments/d17daff5-b3b7-4e4d-bc67-78532fd33510) | Test file: [Material_GlassBSDF.blend](https://projects.blender.org/attachments/357fdeeb-7f04-4ef8-afcc-5f6a7153ab6e)

March05_TransmissionDirect.jpg

129 KiB

March06_TransmissionDirect.jpg

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Eric Klein added the

labels 2023-05-24 01:20:28 +02:00

Pratik Borhade commented

2023-05-29 05:43:45 +02:00

Hi, thanks for the report. Could you check whether its fixed in recent 3.6 build after #108125: https://builder.blender.org/download/daily/

Also, I'm not able to locate BMW file on demo-files page

Hi, thanks for the report. Could you check whether its fixed in recent 3.6 build after #108125: https://builder.blender.org/download/daily/ Also, I'm not able to locate BMW file on demo-files page

Pratik Borhade added

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Needs Information from User

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Status

Needs Triage

labels 2023-05-29 05:44:27 +02:00

Eric Klein commented

2023-05-29 09:09:34 +02:00

The latest 3.6 beta and 4.0 alpha from 5/29/2023. It does not resolve it. As mention above looks like the commits from Lukas Stockner on 3-25-2023. The "Cycles: Use per-microfacet Fresnel term for Glass closures" or "Cycles: Make Fresnel term independent of microfacet closure type" broke the transmission render passes.

Below is simple glass ball the cycles viewport shading is setup for "Transmission Indirect" pass. See attach blend file Material_GlassBSDF.blend.

3.51
Correct "Transmission Indirect" pass for the ball with the GlassBSDF material.

3.60 beta or 4.00 alpha
Notice the over bright image data from the ball with the GlassBSDF. If you connect the PrincipleBSDF setup as glass material with "Transmission" value 1.0 it looks the same as 3.51.

The latest 3.6 beta and 4.0 alpha from 5/29/2023. It does not resolve it. As mention above looks like the commits from Lukas Stockner on 3-25-2023. The "Cycles: Use per-microfacet Fresnel term for Glass closures" or "Cycles: Make Fresnel term independent of microfacet closure type" broke the transmission render passes. Below is simple glass ball the cycles viewport shading is setup for "Transmission Indirect" pass. See attach blend file Material_GlassBSDF.blend. 3.51 Correct "Transmission Indirect" pass for the ball with the GlassBSDF material. ![image](/attachments/0bb807d3-139b-4211-b227-450a1465ef4c) 3.60 beta or 4.00 alpha Notice the over bright image data from the ball with the GlassBSDF. If you connect the PrincipleBSDF setup as glass material with "Transmission" value 1.0 it looks the same as 3.51. ![image](/attachments/0dd22b28-971e-4cfa-9a1a-e3e071b45f7c)

image.png

462 KiB

image.png

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Material_GlassBSDF.blend

969 KiB

Pratik Borhade commented

2023-05-29 12:11:40 +02:00

Thanks. Can confirm the regression (broke between 6b8cdd597996 - 175b1b449ec2).
I think your findings are correct. This is very likely affected by 014f6e4309 / 5f9b518a8b
cc @LukasStockner

Thanks. Can confirm the regression (broke between `6b8cdd597996 - 175b1b449ec2`). I think your findings are correct. This is very likely affected by 014f6e4309 / 5f9b518a8b cc @LukasStockner

Pratik Borhade added

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Needs Information from User

labels 2023-05-29 12:18:54 +02:00

Lukas Stockner referenced this issue from a commit

2023-05-30 00:17:27 +02:00

Fix #108211: Incorrect Transmission Color pass due to merged Glass closure

Lukas Stockner closed this issue

2023-05-30 00:36:25 +02:00

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labels 2023-05-30 00:36:27 +02:00

Lukas Stockner referenced this issue

2023-05-30 01:01:23 +02:00

Cycles: Remove MultiGGX code, replace with albedo scaling #107958

Eric Klein commented

2023-05-30 09:59:52 +02:00

The latest commit did solved the issue for the simple ball GlassBSDF. It failed in a slightly more complex setup. Below is simple glass car setup where transmission direct fails for GlassBSDF in the latest 3.60 beta, but works fine in 3.51 or replacing the GlassBSDF with the PrincipleBSDF configure as a glass shader with transmission of 1.0. See attach "CarGlassBSDF_Bright.blend".

3.51 Transmission Direct with GlassBSDF

3.60 beta with your latest commit - Transmission Direct with GlassBSDF.

The latest commit did solved the issue for the simple ball GlassBSDF. It failed in a slightly more complex setup. Below is simple glass car setup where transmission direct fails for GlassBSDF in the latest 3.60 beta, but works fine in 3.51 or replacing the GlassBSDF with the PrincipleBSDF configure as a glass shader with transmission of 1.0. See attach "CarGlassBSDF_Bright.blend". 3.51 Transmission Direct with GlassBSDF ![image](/attachments/842b8b8a-d441-4ceb-892b-9dafc3fdb424) 3.60 beta with your latest commit - Transmission Direct with GlassBSDF. ![image](/attachments/8d6236f3-b639-4e36-ae9a-4cc7c2c0a587)

image.png

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image.png

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CarGlassBSDF_Bright.blend

4.9 MiB

Eric Klein reopened this issue

2023-05-30 09:59:54 +02:00

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labels 2023-05-30 10:00:23 +02:00

Pratik Borhade commented

2023-06-05 06:04:10 +02:00

confirming again.

Pratik Borhade added

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labels 2023-06-05 06:04:36 +02:00

Lukas Stockner commented

2023-06-08 03:17:26 +02:00

Hm, yeah, the issue here is that the current code expects each closure to be diffuse OR glossy OR transmissive, so the unified Glass closure can't end up writing to glossy and transmission.

Should be doable to change that logic specifically for Glass, I'll have a look.

Hm, yeah, the issue here is that the current code expects each closure to be diffuse OR glossy OR transmissive, so the unified Glass closure can't end up writing to glossy and transmission. Should be doable to change that logic specifically for Glass, I'll have a look.

Lukas Stockner commented

2023-06-12 12:48:06 +02:00

FYI, the fix is in this branch, I can't create a PR into the release branch currently: https://projects.blender.org/LukasStockner/blender/src/branch/glass-albedo-fix

Eric Klein commented

2023-06-12 23:46:04 +02:00

I check the "glass-albedo-fix" branch and can confirm that the fix for the glass transmission passes is working in this branch.

Thanks for looking into this bug.

I check the "glass-albedo-fix" branch and can confirm that the fix for the glass transmission passes is working in this branch. Thanks for looking into this bug.

Lukas Stockner referenced this issue from a commit

2023-06-13 01:35:40 +02:00

Fix #108211: Cycles: Correctly split Glass BSDF contributions

Lukas Stockner closed this issue

2023-06-13 01:57:18 +02:00

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labels 2023-06-13 01:57:20 +02:00