feat: lighting for rain and snow

[doodlum]

Summary by CodeRabbit

• New Features
  • Enhanced particle lighting with per-fragment lighting accumulation for richer visuals.
  • Added clustered light sampling and optional inverse-square lighting for more accurate illumination.
  • Improved light attenuation and shadow-aware contributions for more realistic particle appearance.
  • Particles now incorporate directional and ambient lighting data for consistent scene integration.

[coderabbitai[bot]]

Walkthrough

Added per-fragment lighting to the particle shader: vertex shader now outputs view-space position, and pixel shader accumulates directional, ambient, and clustered light contributions with conditional attenuation and compile-time includes.

Changes

Cohort / File(s)

Summary

Particle shader package/Shaders/Particle.hlsl

Added float3 ViewPositionVS : TEXCOORD2 to VS_OUTPUT. Vertex shader propagates view-space position. Pixel shader replaced single ColorScale path with per-fragment lighting: reads directional & ambient from SharedData.hlsli, computes world position, conditionally samples clustered lights via LightLimitFix.hlsli and applies attenuation via InverseSquareLighting.hlsli when enabled. Added conditional include directives and light accumulation loop.

Sequence Diagram

sequenceDiagram
    participant VS as Vertex Shader
    participant PS as Pixel Shader
    participant Cluster as Light Cluster (LightLimitFix)
    participant Math as Lighting Math

    VS->>VS: compute finalViewPosition
    VS->>VS: vsout.ViewPosition = finalViewPosition.xyz
    VS-->>PS: emit VS_OUTPUT (with ViewPositionVS)

    PS->>PS: sample baseColor
    PS->>PS: read directional & ambient (SharedData)
    PS->>PS: propertyColor = dir+ambient
    PS->>PS: worldPos = ViewToWorld * ViewPositionVS

    rect rgb(235,245,255)
    Note over PS,Cluster: if LIGHT_LIMIT_FIX defined
    PS->>Cluster: fetch lights for fragment/cluster
    Cluster-->>PS: list of lights
    end

    loop for each light
        PS->>Math: compute lightDir, distance
        alt ISL enabled
            Math-->>PS: inverse-square attenuation
        else
            Math-->>PS: quadratic falloff attenuation
        end
        PS->>PS: accumulate propertyColor += lightContribution
    end

    PS->>PS: finalColor = propertyColor * baseColor
    PS-->>PS: output final fragment color

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐇 I nudged view pos into the vertex stream,
Collected suns within each tiny gleam,
Direction, ambient, clusters in a swirl,
Each particle now catches light and twirls,
Shader hops brighter — a luminous dream.

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 succinctly conveys the primary change of this pull request, which is adding lighting support specifically for rain and snow particles in the shader. It aligns with the code modifications that introduce per-fragment lighting, directional and ambient contributions, and cluster light integration for particle effects. Therefore, it accurately captures the main purpose of the changes without unnecessary detail.
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 particle-lighting

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[github-actions[bot]]

Using provided base ref: 79aebb6df5a67064a4380ac3763965f400afbe58 Using base ref: 79aebb6df5a67064a4380ac3763965f400afbe58 Base commit date: 2025-10-18T22:52:09+01:00 (Saturday, October 18, 2025 10:52 PM) No actionable suggestions for changed features.