fix(grass collision): clamp maximum depth of grass

[doodlum]

Summary by CodeRabbit

• Chores

  • Version updated to 3.0.2.

• Bug Fixes

  • Improved grass collision calculations to enhance accuracy and consistency in collision response handling.

[coderabbitai]

Walkthrough

The pull request bumps the grass collision shader version from 3-0-1 to 3-0-2 and refactors the collision depth clamping logic in the GetCollision function from post-accumulation clamping to per-sample clamping before accumulation.

Changes

Cohort / File(s)	Summary
Version update features/Grass Collision/Shaders/Features/GrassCollision.ini	Version bumped from 3-0-1 to 3-0-2
Clamping logic refactor features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli	Per-sample collision depth clamping now applied within term computation using max(0, min(maximumDepth, ...)) instead of post-accumulation clamping; applied to both collisionAmount and previousCollisionAmount with associated ProceduralAnimation terms

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

The changes are localized to a single function with a clear clamping pattern refactor, but shader code context and collision behavior verification require focused attention.

Possibly related PRs

• chore(grass collision): simpler grass collision #1525: Modifies the collision loop and GetCollision behavior in the same grass collision shader implementation.
• feat(grass collision): implement with texture and history #1539: Directly related—introduces or rewrites the GetCollision implementation that this PR modifies with per-sample clamping adjustments.

Suggested reviewers

• alandtse

Poem

A rabbit hops through grassy terrain,
Where collisions now clamp with care and restraint,
Per-sample precision, no more delay,
The shader dances in a cleaner way,
Version 3-0-2—hopping's more graceful today! 🐰✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The pull request title "fix(grass collision): clamp maximum depth of grass" is directly related to and accurately summarizes the main change in the PR. The primary functional modification in GrassCollision.hlsli refactors how maximum depth clamping is applied in the GetCollision function—shifting from post-accumulation clamping to per-sample clamping within term computation. The title clearly captures this core objective using conventional commit formatting with an appropriate "fix" scope and specific description. The secondary version bump in the .ini file is a natural consequence of the functional fix rather than the main change.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch grass-collision-clamp

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📜 Recent review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 79aebb6 and c72619f.

📒 Files selected for processing (2)

• features/Grass Collision/Shaders/Features/GrassCollision.ini (1 hunks)
• features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli (1 hunks)

🧰 Additional context used

📓 Path-based instructions (2)

**/*.{cpp,cxx,cc,c,h,hpp,hxx,hlsl,hlsli,fx,fxh,py}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

Do not include TODO/FIXME placeholders; provide complete, working solutions

Files:

• features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli

features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh}: Place all feature shaders under features/YourFeature/Shaders/
Avoid GPU register/buffer conflicts in HLSL; verify register usage (e.g., with hlslkit buffer scanning)

Files:

• features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: Validate shader compilation (Flatrim, .github/configs/shader-validation.yaml)
• GitHub Check: Validate shader compilation (VR, .github/configs/shader-validation-vr.yaml)
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🔇 Additional comments (3)

features/Grass Collision/Shaders/Features/GrassCollision.ini (1)

2-2: LGTM! Version bump aligns with shader changes.

The version increment from 3-0-1 to 3-0-2 appropriately reflects the collision depth clamping refactor in the associated shader file.

features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli (2)

71-71: Improved per-sample depth clamping.

The refactoring from post-accumulation clamping to per-sample clamping is a solid improvement. By limiting each sample's depth contribution to [0, maximumDepth] before multiplying by the procedural animation weight and bilinear weight, the code now prevents individual outlier collision samples from dominating the weighted average. This is more physically accurate than clamping the accumulated result.

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74-74: Consistent per-sample clamping for previous collision.

The same per-sample clamping pattern applied to previousCollisionAmount ensures consistent behavior between current and previous collision calculations, which is essential for smooth temporal blending.

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[github-actions]

Using provided base ref: 79aebb6
Using base ref: 79aebb6
Base commit date: 2025-10-18T22:52:09+01:00 (Saturday, October 18, 2025 10:52 PM)
No actionable suggestions for changed features.

[github-actions]

✅ A pre-release build is available for this PR:
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