chore(grass collision): less aggressive

[doodlum]

Summary by CodeRabbit

• Bug Fixes
  • Improved grass collision visuals by refining normal calculations, reducing shading artifacts and flicker.
  • Reduced collision displacement strength by 25% for more natural bending and less over-shooting.
  • Smoothed frame-to-frame displacement to minimize jitter and popping during movement.
  • Enhanced stability in dense collision scenarios, lowering the chance of visual clipping.
  • Achieves more consistent results across varied terrain scales, improving overall realism without impacting performance.

[coderabbitai]

Walkthrough

Adjusted grass collision shader math: rescaled normal computation weights in ComputeNormalFromHeights and reduced both current and previous displacement magnitudes by multiplying with 0.75 in GetDisplacedPosition. No exported/public signatures were changed.

Changes

Cohort / File(s)	Summary of Changes
Grass collision shader tuning features/Grass Collision/Shaders/GrassCollision/GrassCollision.hlsli	- ComputeNormalFromHeights: scale vector changed from float3(1000.0, 1000.0, 0.0001) to float3(1.0, 1.0, 0.1) - GetDisplacedPosition: apply 0.75 factor to both displacement and previousDisplacement (collision × alpha × 0.75) - No public/exported signatures modified

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor CPU
  participant VS as Vertex/Compute Shader
  participant Func1 as ComputeNormalFromHeights
  participant Func2 as GetDisplacedPosition
  participant OUT as Output Position/Normal

  CPU->>VS: Provide height/collision data, alpha
  VS->>Func1: Sample heights
  Note right of Func1: Rescaled normal weights (1.0,1.0,0.1)
  Func1-->>VS: Normal
  VS->>Func2: collision, previousCollision, alpha
  Note right of Func2: Apply 0.75 to displacement terms
  Func2-->>VS: Displaced position
  VS-->>OUT: Output displaced position and normal

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• chore(grass collision): simpler grass collision #1525 — Also adjusts GrassCollision.hlsli collision/alpha scaling and related math, overlapping in shader logic changes.

Poem

A tuft, a sway, the blades align,
I tweak the normals, make them fine.
A softer step, 0.75’s grace,
The grasses bow with measured pace.
Hippity-hop through fields I tread—
With gentler math beneath my spread. 🌿🐇

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 title “chore(grass collision): less aggressive” clearly and concisely summarises the primary change of reducing the intensity of grass collision by adjusting normal calculation and displacement factors, matching the modifications in the changeset.
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 less-aggressive-grass-collision

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📥 Commits

Reviewing files that changed from the base of the PR and between 5fc0ef9 and 63d1d05.

📒 Files selected for processing (1)

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

🧰 Additional context used

📓 Path-based instructions (2)

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

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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

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🔇 Additional comments (2)

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

99-99: LGTM! Normal scaling adjustment achieves the intended goal.

The change to float3(1.0, 1.0, 0.1) increases the z-component's relative influence on the computed normal by approximately 1000x compared to the previous float3(1000.0, 1000.0, 0.0001). This makes the normals less steep and reduces the aggressiveness of the collision response, which aligns with the PR objective.

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156-157: LGTM! Displacement reduction achieves the intended goal.

The addition of the 0.75 multiplier reduces both current and previous displacement magnitudes by 25%, directly decreasing the visual impact of grass collision. This change, combined with the normal scaling adjustment, effectively makes the grass collision less aggressive as intended.

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[github-actions]

Using provided base ref: 5fc0ef9
Using base ref: 5fc0ef9
Base commit date: 2025-10-05T23:02:41+01:00 (Sunday, October 05, 2025 11:02 PM)
No actionable suggestions for changed features.

[github-actions]

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