Extreme Normal editing causes flat shading #88170

New Issue

炎臻 · 2021-05-10T10:53:22+02:00

炎臻 commented

2021-05-10 10:53:22 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.27

Blender Version
Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-05-08 23:52, hash: 3c7b80ae2c
Worked: 2.92.0

Caused by 1c22b551d0

Short description of error:

Extreme Normal editing(like flipping the normal and using other normal editing modifiers) causes flat shading.

In the image above,the sphere has a Data Transfer modifier which is receiving the Normals of the plane.
As in the upper image(2.92.0),the sphere is shaded smooth while in the lower image(2.93 beta) it gets flat shading at some faces.

Exact steps for others to reproduce the error

{icon fa-plus} OS Conditon: WIN 10 |Blender: 2.93.0 Beta

Default scene with default cube deleted.
Add a sphere object and a plane,add a Data Tansfer modifier to the sphere which transfers the normals of the plane to the sphere.
Have the sphere some negative Z axis transformation then observe its normal,the flat shading should be appearing at some angle.
{icon bicycle spin} Below is a blend file with the setup above with an additional shading node in the material:
This is the additional node which filps the normals of the geometry:
And the results in the respective versions:

NormalFlatShadingBug.blend

From #111805:

2.92	2.93

shadingBug.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.27 **Blender Version** Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-05-08 23:52, hash: `3c7b80ae2c` Worked: 2.92.0 Caused by 1c22b551d0 --- ## Short description of error: Extreme Normal editing(like flipping the normal and using other normal editing modifiers) causes flat shading. ![2.92.0.png](https://archive.blender.org/developer/F10074818/2.92.0.png) ![2.93.png](https://archive.blender.org/developer/F10074764/2.93.png) In the image above,the sphere has a Data Transfer modifier which is receiving the Normals of the plane. As in the upper image(2.92.0),the sphere is shaded smooth while in the lower image(2.93 beta) it gets flat shading at some faces. --- ## Exact steps for others to reproduce the error {icon fa-plus} OS Conditon: **WIN 10** |Blender: **2.93.0 Beta** - Default scene with default cube deleted. - Add a sphere object and a plane,add a Data Tansfer modifier to the sphere which transfers the normals of the plane to the sphere. - Have the sphere some negative Z axis transformation then observe its normal,the flat shading should be appearing at some angle. {icon bicycle spin} Below is a blend file with the setup above with an additional shading node in the material: This is the additional node which filps the normals of the geometry: ![shader node.png](https://archive.blender.org/developer/F10074849/shader_node.png) And the results in the respective versions: ![2.92.0(2).png](https://archive.blender.org/developer/F10074857/2.92.0_2_.png) ![2.93 beta.png](https://archive.blender.org/developer/F10074859/2.93_beta.png) [NormalFlatShadingBug.blend](https://archive.blender.org/developer/F10074867/NormalFlatShadingBug.blend) --- From #111805: | 2.92 | 2.93 | | --- | --- | | ![image.png](attachments/9115479c-715e-4144-97cb-af6acf63bb8b) | ![image.png](attachments/c1b7140a-bd63-49c7-8d1d-353e2b790d3f) | [shadingBug.blend](attachments/aeee05e6-9f12-4062-a280-99996f44df82)

炎臻 commented

2021-05-10 10:53:22 +02:00

Added subscriber: @PrettyFireNOI7

blender-admin commented

2021-05-10 10:53:22 +02:00

#88400 was marked as duplicate of this issue

Philipp Oeser commented

2021-05-10 13:29:55 +02:00

Added subscribers: @fclem, @lichtwerk

Philipp Oeser commented

2021-05-10 13:29:55 +02:00

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

Philipp Oeser commented

2021-05-10 13:29:55 +02:00

I can confirm the change in behavior since 1c22b551d0, so in most situations this is an improvement and an intentional change.

However, I am a bit confused here, since Cycles and Eevee dont seem to behave the same (as the commit message promised), see e.g. this file:
repro.blend

Changing Cycles <> Eevee shows a clear difference here.

This might all be expected behavior, but to be sure, I would kindly ask @fclem to have a look.

I can confirm the change in behavior since 1c22b551d0, so in most situations this is an improvement and an intentional change. However, I am a bit confused here, since Cycles and Eevee dont seem to behave the same (as the commit message promised), see e.g. this file: [repro.blend](https://archive.blender.org/developer/F10075408/repro.blend) Changing Cycles <> Eevee shows a clear difference here. This might all be expected behavior, but to be sure, I would kindly ask @fclem to have a look.

Clément Foucault commented

2021-05-12 15:01:20 +02:00

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

Clément Foucault commented

2021-05-12 15:01:20 +02:00

This is due to a difference between Cycles and EEVEE.

EEVEE applies ensure_valid_reflection on glossy normal input where Cycles only applies it on normal mapped & bump node output.

Here is an example of the same behavior in cycles.

Unfortunately, we need to use ensure_valid_reflection to avoid nasty artifacts on glossy BSDF even without bump/normal mapping (see #81070 & #78501).

We keep the same behavior when SSR is off to keep consistency.

Note that EEVEE won't distort the normals for diffuse.

This is due to a difference between Cycles and EEVEE. EEVEE applies `ensure_valid_reflection` on glossy normal input where Cycles only applies it on normal mapped & bump node output. Here is an example of the same behavior in cycles. ![Capture d’écran du 2021-05-12 14-53-15.png](https://archive.blender.org/developer/F10087831/Capture_d_écran_du_2021-05-12_14-53-15.png) Unfortunately, we need to use `ensure_valid_reflection` to avoid nasty artifacts on glossy BSDF even without bump/normal mapping (see #81070 & #78501). We keep the same behavior when SSR is off to keep consistency. Note that EEVEE won't distort the normals for diffuse.

炎臻 commented

2021-05-13 06:47:18 +02:00

In #88170#1159717, @fclem wrote:
This is due to a difference between Cycles and EEVEE.

EEVEE applies ensure_valid_reflection on glossy normal input where Cycles only applies it on normal mapped & bump node output.

Here is an example of the same behavior in cycles.

Unfortunately, we need to use ensure_valid_reflection to avoid nasty artifacts on glossy BSDF even without bump/normal mapping (see #81070 & #78501).

We keep the same behavior when SSR is off to keep consistency.

Note that EEVEE won't distort the normals for diffuse.

Thanks for elaborating.I had already found out how the fixed reflection( #81070 & #78501 ) improved my own scene too thanks to Philipp Oeser's reply.
I just would like to have a way to make the flatten shading smooth.
I used to use these normal editing tricks(like the report above) to realize some of my rendering ideas.
And now it looks like this:

Nodes and files:

Sample.blend

So if the reflecion fix must come with this normal shading behavior change then I would look for other way to build my shader.

> In #88170#1159717, @fclem wrote: > This is due to a difference between Cycles and EEVEE. > > EEVEE applies `ensure_valid_reflection` on glossy normal input where Cycles only applies it on normal mapped & bump node output. > > Here is an example of the same behavior in cycles. > > ![Capture d’écran du 2021-05-12 14-53-15.png](https://archive.blender.org/developer/F10087831/Capture_d_écran_du_2021-05-12_14-53-15.png) > > Unfortunately, we need to use `ensure_valid_reflection` to avoid nasty artifacts on glossy BSDF even without bump/normal mapping (see #81070 & #78501). > > We keep the same behavior when SSR is off to keep consistency. > > Note that EEVEE won't distort the normals for diffuse. Thanks for elaborating.I had already found out how the fixed reflection( #81070 & #78501 ) improved my own scene too thanks to __Philipp Oeser__'s reply. I just would like to have a way to make the flatten shading smooth. I used to use these normal editing tricks(like the report above) to realize some of my rendering ideas.![2.92.0.png](https://archive.blender.org/developer/F10090331/2.92.0.png) And now it looks like this:![2.93beta.png](https://archive.blender.org/developer/F10090346/2.93beta.png) --- Nodes and files: ![NodeSetUp.png](https://archive.blender.org/developer/F10090351/NodeSetUp.png) [Sample.blend](https://archive.blender.org/developer/F10090353/Sample.blend) --- So if the reflecion fix must come with this normal shading behavior change then I would look for other way to build my shader.

Philipp Oeser commented

2021-05-19 16:20:45 +02:00

Added subscriber: @jk137574

Philipp Oeser commented

2021-05-19 16:23:59 +02:00

We keep the same behavior when SSR is off to keep consistency.

In a way, this removes a whole range of shading possibilities (maybe not do it when SSR is OFF?)

> We keep the same behavior when SSR is off to keep consistency. In a way, this removes a whole range of shading possibilities (maybe not do it when SSR is OFF?)

Philipp Oeser removed the

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Extreme Normal editing causes flat shading #88170

Short description of error:

Exact steps for others to reproduce the error