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skybox.wgsl: Fix precision issues #9909

Merged
merged 3 commits into from
Sep 23, 2023
Merged

skybox.wgsl: Fix precision issues #9909

merged 3 commits into from
Sep 23, 2023

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superdump
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Objective

Solution

  • At large translations (a few thousand units), the precision of calculating the ray direction from the fragment world position and camera world position seems to break down. Sampling the cubemap only needs the ray direction. As such we can use the view space fragment position, normalise it, rotate it to world space, and use that.

Changelog

  • Fixed: Jittery skybox at large translations.

@superdump superdump requested review from JMS55 and robtfm September 23, 2023 11:02
robtfm
robtfm reviewed Sep 23, 2023
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crates/bevy_core_pipeline/src/skybox/skybox.wgsl Outdated Show resolved Hide resolved
crates/bevy_core_pipeline/src/skybox/skybox.wgsl Outdated
1.0,
1.0
);
let view_position = view_position_homogeneous.xyz / view_position_homogeneous.w;
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view_position_homogeneous.w is constant 1.0 from above

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Right, copy pasta.

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Actually no. This was wrong. The vec4 position is multiplied by the inverse projection matrix, so the resulting w is not guaranteed to be 1.0.

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oops right

crates/bevy_core_pipeline/src/skybox/skybox.wgsl Outdated Show resolved Hide resolved
@superdump superdump added this pull request to the merge queue Sep 23, 2023
Merged via the queue into bevyengine:main with commit 22dfa9e Sep 23, 2023
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rdrpenguin04 pushed a commit to rdrpenguin04/bevy that referenced this pull request Jan 9, 2024
@superdump
skybox.wgsl: Fix precision issues (bevyengine#9909)
0339338 
# Objective

- Fixes bevyengine#9707 

## Solution

- At large translations (a few thousand units), the precision of
calculating the ray direction from the fragment world position and
camera world position seems to break down. Sampling the cubemap only
needs the ray direction. As such we can use the view space fragment
position, normalise it, rotate it to world space, and use that.

---

## Changelog

- Fixed: Jittery skybox at large translations.
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@robtfm robtfm robtfm approved these changes

@JMS55 JMS55 JMS55 approved these changes

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Successfully merging this pull request may close these issues.

Bevy Skybox Jittering/Pixelating at Medium/Large Translations
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@superdump @JMS55 @robtfm