blender 4.0 : Transmission Roughness is missing in Principled BSDF, preventing some textures from being used correctly in previous versions #114956

New Issue

Damao · 2023-11-16T04:37:34+01:00

Damao commented

2023-11-16 04:37:34 +01:00

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.58

Blender Version
Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: 878f71061b8e
Worked: (newest version of Blender that worked as expected)

Short description of error
[Transmission Roughness is missing in Principled BSDF, preventing some textures from being used correctly in previous versions.]

Exact steps for others to reproduce the error [In Blender 4.0, there is a lack of Transmission Roughness in the Principled BSDF.
[Started to appear in Blender 4.0.]
[In Blender 3.6 it was very easy to make a Transmission material with a smooth exterior and a rough interior, by adjusting the Transmission Roughness].

[And in blender 4.0, due to the lack of Transmission Roughness, the material cannot be displayed correctly. And in blender 4.0 it's not possible to make this effect fast]

[Based on the default startup or an attached .blend file (as simple as possible)]]

**System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.58 **Blender Version** Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: `878f71061b8e` Worked: (newest version of Blender that worked as expected) **Short description of error** [Transmission Roughness is missing in Principled BSDF, preventing some textures from being used correctly in previous versions.] **Exact steps for others to reproduce the error** [In Blender 4.0, there is a lack of Transmission Roughness in the Principled BSDF. [Started to appear in Blender 4.0.] [In Blender 3.6 it was very easy to make a Transmission material with a smooth exterior and a rough interior, by adjusting the Transmission Roughness]. ![a19f5d5cd9e1b53fa887da94db5c63d](/attachments/d1890297-3da2-456a-8a4f-e8eb9fd2ea85) [And in blender 4.0, due to the lack of Transmission Roughness, the material cannot be displayed correctly. And in blender 4.0 it's not possible to make this effect fast] ![image](/attachments/4bebe34e-9d6d-402d-aea7-c6b18caec210) [Based on the default startup or an attached .blend file (as simple as possible)]]

111.blend

1.2 MiB

image.png

1.3 MiB

a19f5d5cd9e1b53fa887da94db5c63d.png

995 KiB

Damao added the

labels 2023-11-16 04:37:35 +01:00

Damao changed title from ~~Transmission Roughness is missing in Principled BSDF, preventing some textures from being used correctly in previous versions~~ to blender 4.0 : Transmission Roughness is missing in Principled BSDF, preventing some textures from being used correctly in previous versions

2023-11-16 04:59:24 +01:00

Pratik Borhade commented

2023-11-16 07:32:03 +01:00

Hi, thanks for the report. Hm the socket was removed intentionally in 89218b66c2 but reason is not very clear. Neither I found any reference in release notes.
cc @LukasStockner

Hi, thanks for the report. Hm the socket was removed intentionally in 89218b66c2192f6d517776211855f0306c3d5f57 but reason is not very clear. Neither I found any reference in release notes. cc @LukasStockner

👍 1

Pratik Borhade added

Module

Render & Cycles

Status

Needs Info from Developers

and removed

Status

Needs Triage

labels 2023-11-16 07:32:29 +01:00

Tomás Cejas commented

2023-11-16 12:37:36 +01:00

You can use the following setup to recreate the effect in 4.0: https://i.imgur.com/KQBrooF.png
Source: reddit blender help post: https://www.reddit.com/r/blenderhelp/comments/16z6tld/how_to_get_sharp_reflections_but_rough/

But I would indeed prefer to have a transmission roughness socket.

You can use the following setup to recreate the effect in 4.0: https://i.imgur.com/KQBrooF.png Source: reddit blender help post: https://www.reddit.com/r/blenderhelp/comments/16z6tld/how_to_get_sharp_reflections_but_rough/ But I would indeed prefer to have a transmission roughness socket.

👍 1

xZaki commented

2023-11-16 16:03:45 +01:00

A similar enough effect can be easily made with coat.

The reason transmission roughness was removed was because it was a hack for a thin sheet mode, and a proper one is planned to be added at some point in the future.

A similar enough effect can be easily made with coat. ![image](/attachments/e9be1af0-2617-469e-a61b-68f466742704) ![image](/attachments/9e45a74b-5bdc-4d3a-a83e-05bc30aed215) The reason transmission roughness was removed was because it was a hack for a thin sheet mode, and a proper one is planned to be added at some point in the future.

image.png

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image.png

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👍 1

Damao commented

2023-11-16 17:19:39 +01:00

A similar enough effect can be easily made with coat.

The reason transmission roughness was removed was because it was a hack for a thin sheet mode, and a proper one is planned to be added at some point in the future.

Thanks, I know how to use it.

> A similar enough effect can be easily made with coat. > ![image](/attachments/e9be1af0-2617-469e-a61b-68f466742704) > ![image](/attachments/9e45a74b-5bdc-4d3a-a83e-05bc30aed215) > The reason transmission roughness was removed was because it was a hack for a thin sheet mode, and a proper one is planned to be added at some point in the future. Thanks, I know how to use it.

Lukas Stockner commented

2023-11-18 19:48:49 +01:00

Yeah, the socket was removed intentionally.

The reason is that many assumptions of the new Fresnel handling, new multiscattering approximation etc. rely on specular and transmission using the same microfacet interface.

I can go into more detail if needed, but the short version is: This is a physically-based model, and from a physical perspective it makes no sense to have different roughness. There is only one medium boundary, and that boundary has one roughness, and it causes both effects.

Sometimes ignoring/overriding physical effects for artistic control makes sense, but this one would cause too many issues and prevent too many other things if we supported it, so it's gone now. You might notice that it was already disabled when using Multiscattering GGX in 3.6.

Yeah, the socket was removed intentionally. The reason is that many assumptions of the new Fresnel handling, new multiscattering approximation etc. rely on specular and transmission using the same microfacet interface. I can go into more detail if needed, but the short version is: This is a physically-based model, and from a physical perspective it makes no sense to have different roughness. There is only one medium boundary, and that boundary has one roughness, and it causes both effects. Sometimes ignoring/overriding physical effects for artistic control makes sense, but this one would cause too many issues and prevent too many other things if we supported it, so it's gone now. You might notice that it was already disabled when using Multiscattering GGX in 3.6.

Damao closed this issue

2023-11-19 03:15:18 +01:00

Blender Bot added

Status

Archived

and removed

Status

Needs Info from Developers

labels 2023-11-19 03:15:20 +01:00

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