fix(PBR): skip IrradianceToLinear on specular in vanilla

[Dlizzio]

Summary by CodeRabbit

• Bug Fixes
  • Corrected specular color handling in shader rendering to ensure proper lighting appearance based on build configuration.

[coderabbitai]

📝 Walkthrough

Walkthrough

A conditional preprocessor guard is added to the specular color gamma-to-linear conversion in Lighting.hlsl, restricting it to non-TRUE_PBR builds. This aligns the code with the distinction that Vanilla specular requires conversion while PBR specular is already linear.

Changes

Cohort / File(s)	Summary
Specular Color Gamma Conversion package/Shaders/Lighting.hlsl	Wrapped IrradianceToLinear conversion of specularColor in a #ifndef TRUE_PBR preprocessor conditional, ensuring the conversion only applies to Vanilla specular paths while excluding PBR builds where specular is already linear.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related PRs

• #1404: Modifies specular handling in the same shader file for PBR deferred paths and gamma-to-linear conversion logic.
• #1327: Changes specular color computation in the pixel shader of the same file, affecting related specular calculation code paths.

Suggested reviewers

• jiayev
• doodlum

Poem

🐰 A shader tweak, so small yet true,
PBR specular needs no gamma brew,
Vanilla glows in linear light,
Conditional guards make it right! ✨

🚥 Pre-merge checks | ✅ 3

✅ 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 accurately describes the main change: conditionally skipping IrradianceToLinear conversion on specular color in vanilla (non-PBR) builds.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[github-actions]

Using provided base ref: 22fbc96
Using base ref: 22fbc96
Base commit date: 2026-02-07T19:27:40Z (Saturday, February 07, 2026 07:27 PM)
No actionable suggestions for changed features.

[github-actions]

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