Cycles: Only apply bake ray nudging on objects with smooth normals #120773

Alaska · 2024-04-18T09:25:02+02:00

Alaska commented

2024-04-18 09:25:02 +02:00

When baking textures from the perspective of the camera, nudging is
applied to the ray direction to avoid discontinuities on triangles with
smooth shading viewed from grazing angles.

This commit disables this feature on triangles that use flat shading
as this feature does not help in the case of flat shading, and actually
causes distortions to surfaces viewed from grazing angles.

When baking textures from the perspective of the camera, nudging is applied to the ray direction to avoid discontinuities on triangles with smooth shading viewed from grazing angles. This commit disables this feature on triangles that use flat shading as this feature does not help in the case of flat shading, and actually causes distortions to surfaces viewed from grazing angles.

Alaska added the

Module

Render & Cycles

label 2024-04-18 09:25:02 +02:00

Alaska added 1 commit 2024-04-18 09:25:09 +02:00

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2a5c426b6b Only apply smooth normal adjustments during baking on objects with smooth normals

Alaska requested review from Brecht Van Lommel 2024-04-18 09:25:24 +02:00

Alaska requested review from Sergey Sharybin 2024-04-18 09:25:31 +02:00

Alaska requested review from Lukas Stockner 2024-04-18 09:25:38 +02:00

Alaska referenced this pull request

2024-04-18 09:29:12 +02:00

Incorrect reflection baking at steep angles in cycles renderer #120729

Brecht Van Lommel commented

2024-04-18 18:04:15 +02:00

@blender-bot build

Brecht Van Lommel approved these changes 2024-04-18 18:04:23 +02:00

Dismissed

Alaska changed title from ~~Cycles: Only apply bake normal nudging on objects with smooth normals~~ to Cycles: Only apply bake ray nudging on objects with smooth normals

2024-04-18 18:13:54 +02:00

Alaska commented

2024-04-18 18:23:42 +02:00

I've just now realized that this causes some sort of discontinuity on triangles facing away from the camera. It's visible on the back side of a high poly UV sphere (256 segments, 128 rings).

So I'm just asking that you re-review this based on this information before committing. From what I can tell, the ray nudging was added to avoid discontinuities on triangles facing away from the camera, and so there is some level of importance here.

I've just now realized that this causes some sort of discontinuity on triangles facing away from the camera. It's visible on the back side of a high poly UV sphere (256 segments, 128 rings). So I'm just asking that you re-review this based on this information before committing. From what I can tell, the ray nudging was added to avoid discontinuities on triangles facing away from the camera, and so there is some level of importance here.

Alaska requested review from Brecht Van Lommel 2024-04-18 18:23:50 +02:00

Brecht Van Lommel requested changes 2024-04-22 11:57:52 +02:00

Brecht Van Lommel left a comment

If this is trading one problem for another, I rather not change things here.

If there is a bug report, or example blend or images making the case for why the new behavior is better it can be considered. But otherwise I rather not spend time on this.

If this is trading one problem for another, I rather not change things here. If there is a bug report, or example blend or images making the case for why the new behavior is better it can be considered. But otherwise I rather not spend time on this.

Alaska commented

2024-04-22 12:34:46 +02:00

If this is trading one problem for another, I rather not change things here.

We're trading the problem that triangles facing the camera at grazing angles are distorted when baked using the "bake from active camera" option, for different types of distortions on the triangles facing away from the camera.

Here's some example images:

Angle	Main	Pull request
View of side of sphere
View of back of sphere

I created this pull request (and explored some other ideas) due to this report: #120729
Basically, the user is unable to bake reflections of the ocean at grazing angles due to the code:

if (DN <= surface_normal_offset) {
  D -= N * (DN - surface_normal_offset);
  D = normalize(D);
}

Since the code mainly benefits objects with smooth normals, I thought it would be okay to turn it off for flat normals, but obviously it is changing the behavior here, and whether or not that's okay is review.

This still doesn't resolve the issue that objects with smooth shading have incorrect reflections at grazing angles. So I was investigating other ideas such as: make surface_normal_offset user adjustable, add the option to bypass that code, adjust the formula to reduce the distortion (I still haven't fully figured this one out). If you would prefer one of these other methods, I can create a pull request.

> If this is trading one problem for another, I rather not change things here. We're trading the problem that triangles facing the camera at grazing angles are distorted when baked using the "bake from active camera" option, for different types of distortions on the triangles facing away from the camera. Here's some example images: |Angle|Main|Pull request| |-|-|-| |View of side of sphere|![Main 2.png](/attachments/e030a46d-250f-4d0b-9b91-6648b7b89e01)|![Pull request 2.png](/attachments/38cf6bff-d0a5-4a25-b494-fc7586312356)| |View of back of sphere |![Main 3.png](/attachments/bfb43fc7-7449-4c8a-a30f-62e78222e677)|![Pull request 3.png](/attachments/637823c2-d75c-40b9-83fb-a131c1d5d57e)| |||| --- I created this pull request (and explored some other ideas) due to this report: #120729 Basically, the user is unable to bake reflections of the ocean at grazing angles due to the code: ``` if (DN <= surface_normal_offset) { D -= N * (DN - surface_normal_offset); D = normalize(D); } ``` Since the code mainly benefits objects with smooth normals, I thought it would be okay to turn it off for flat normals, but obviously it is changing the behavior here, and whether or not that's okay is review. This still doesn't resolve the issue that objects with smooth shading have incorrect reflections at grazing angles. So I was investigating other ideas such as: make `surface_normal_offset` user adjustable, add the option to bypass that code, adjust the formula to reduce the distortion (I still haven't fully figured this one out). If you would prefer one of these other methods, I can create a pull request.

Pull request 3.png

1.7 MiB

Main 2.png

2.6 MiB

Pull request 2.png

2.6 MiB

Main 3.png

1.4 MiB

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Cycles: Only apply bake ray nudging on objects with smooth normals #120773

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