fix(hair): remove marschner gamma conversion and clean unused code

[jiayev]

before, it would look too bright in interior by default

Summary by CodeRabbit

• Refactor
  • Simplified gamma correction handling for diffuse lighting in the Marschner hair model.
  • Removed unused commented-out code related to indirect specular lobe weight calculations.

[coderabbitai]

Walkthrough

The update removes the linear-to-gamma conversion for the diffuse direct lighting component in the Marschner hair lighting model within the shader code. Additionally, it deletes two commented-out lines related to dot product calculations for indirect specular lobe weights, streamlining the shader's handling of gamma correction and cleaning up unused code.

Changes

File(s)	Change Summary
features/Hair Specular/Shaders/Hair/Hair.hlsli	Removed gamma conversion for Marschner diffuse direct lighting; deleted unused commented code.

Sequence Diagram(s)

sequenceDiagram
    participant Shader
    participant LightingModel
    participant Color

    Shader->>LightingModel: GetHairDirectLightMarschner()
    LightingModel-->>Shader: dirDiffuse, dirSpecular
    %% Old: Shader->>Color: LinearToGamma(dirDiffuse)
    %% New: (No LinearToGamma on dirDiffuse)
    Shader->>Color: LinearToGamma(dirSpecular)
    Note right of Shader: Only specular is gamma-corrected now

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Possibly related PRs

• feat(hair): hair self-shadow, finished marschner model and hair flow map support #1225: Refactors and extends Marschner lighting, including gamma correction and self-shadowing logic in the same shader functions modified here.

Suggested reviewers

• alandtse

Poem

A tweak to the shader, so subtle and bright,
Marschner’s hair glimmers in more natural light.
Gamma on diffuse, now gone from the code,
Unused lines swept from the rendering road.
With every small hop, the graphics grow clear—
A rabbit’s delight, for changes this year!
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between b4a3328 and b7a9180.

📒 Files selected for processing (1)

• features/Hair Specular/Shaders/Hair/Hair.hlsli (0 hunks)

💤 Files with no reviewable changes (1)

• features/Hair Specular/Shaders/Hair/Hair.hlsli

⏰ Context from checks skipped due to timeout of 90000ms (4)

• GitHub Check: Validate shader compilation (Flatrim, .github/configs/shader-validation.yaml)
• GitHub Check: Validate shader compilation (VR, .github/configs/shader-validation-vr.yaml)
• GitHub Check: Build plugin and addons
• GitHub Check: Feature Version Audit (PR)

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[github-actions]

Using provided base ref: b4a3328
Using base ref: b4a3328
Base commit date: 2025-07-04T22:21:35-07:00 (Friday, July 04, 2025 10:21 PM)
No actionable suggestions for changed features.

[github-actions]

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