fix(hair): remove pbr lighting mult for hair

[jiayev]

This pull request makes a targeted adjustment to the hair rendering logic in the Lighting.hlsl shader. Specifically, it removes the multiplication by Color::PBRLightingScale when calculating outputAlbedo for hair with enabled specular settings, likely to correct or simplify the lighting calculation.

Shader logic update:

• In Lighting.hlsl, the calculation of outputAlbedo for hair with specular enabled now uses only indirectDiffuseLobeWeight, removing the previous scaling by Color::PBRLightingScale.

Summary by CodeRabbit

• Bug Fixes
  • Corrected hair rendering albedo calculation to remove an unintended lighting scale, producing more accurate hair color and brightness.
  • Improves visual consistency of hair across different lighting conditions and scenes.
  • Reduces cases where hair appeared washed out or overly dim when hair rendering is enabled.

[coderabbitai]

Walkthrough

The pixel shader path for hair-enabled builds in package/Shaders/Lighting.hlsl was modified to set outputAlbedo directly from indirectDiffuseLobeWeight, removing multiplication by Color::PBRLightingScale. No public/exported declarations changed.

Changes

Cohort / File(s)	Summary
Hair PS albedo scaling package/Shaders/Lighting.hlsl	In HAIR/CS_HAIR path, outputAlbedo now equals indirectDiffuseLobeWeight; the previous multiplication by Color::PBRLightingScale was removed. No interface changes.

Sequence Diagram(s)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• revert(PBR): revert pbr refactor #1222 — Reverts broader PBR refactor affecting Lighting.hlsl, related to PBR scaling changes.
• fix(hair): hair marschner indirect diffuse inconsistency #1284 — Adjusts hair indirect diffuse processing in Hair.hlsli, adjacent to the changed albedo computation.
• fix(hair): correct hair indirect normal, marschner by default #1515 — Modifies hair IBL/diffuse accumulation in Lighting.hlsl, overlapping shader lighting logic.

Suggested reviewers

• doodlum
• alandtse

Poem

A tuft of light on strands so fair,
I snip the scale with careful care.
Diffuse whispers, pure and bright,
Hop! says the shader, trims the night.
Fur, filaments, softly glow—
A rabbit nods: now albedos show. 🐇✨

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 “fix(hair): remove pbr lighting mult for hair” succinctly describes the primary change by indicating the removal of the PBR lighting multiplication in the hair shader, follows the conventional commit format with a clear scope, and highlights the key modification without extraneous detail.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

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[github-actions]

Using provided base ref: e91f159
Using base ref: e91f159
Base commit date: 2025-09-27T07:51:01+01:00 (Saturday, September 27, 2025 07:51 AM)
No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

package/Shaders/Lighting.hlsl (1)

3101-3109: Optional: guard the hair override to non-PBR to avoid redundant assignment.

When TRUE_PBR is defined, Line 3102 already sets outputAlbedo to indirectDiffuseLobeWeight; the hair block reassigns the same value. To reduce confusion, gate the hair override for non-PBR builds only.

 #if defined(HAIR) && defined(CS_HAIR)
   if (SharedData::hairSpecularSettings.Enabled) {
-    outputAlbedo = indirectDiffuseLobeWeight;
+  #if !defined(TRUE_PBR)
+    // In non-PBR hair builds, drive ambient weighting from diffuse lobe.
+    outputAlbedo = indirectDiffuseLobeWeight;
+  #endif
   }
 #endif

📜 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 e91f159 and 9a11a8f.

📒 Files selected for processing (1)

• package/Shaders/Lighting.hlsl (1 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.{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:

• package/Shaders/Lighting.hlsl

🧠 Learnings (1)

📚 Learning: 2025-08-03T18:37:19.690Z

Learnt from: jiayev
PR: doodlum/skyrim-community-shaders#0
File: :0-0
Timestamp: 2025-08-03T18:37:19.690Z
Learning: ISReflectionsRayTracing.hlsl and ISWorldMap.hlsl in the skyrim-community-shaders repository are image-space post-processing shaders that perform color sampling and blending operations that need proper linear color space handling for the linear lighting system. ISReflectionsRayTracing handles screen-space reflections and should use conditional Color::IrradianceToLinear/Gamma conversions similar to ISCompositeLensFlareVolumetricLighting.hlsl. ISWorldMap performs 7x7 color accumulation that should be done in linear space similar to the pattern used in ISSAOComposite.hlsl.

Applied to files:

• package/Shaders/Lighting.hlsl

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• GitHub Check: Validate shader compilation (Flatrim, .github/configs/shader-validation.yaml)
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🔇 Additional comments (1)

package/Shaders/Lighting.hlsl (1)

3105-3109: Approve hair albedo PBRLightingScale fix. No remaining PBRLightingScale multiplications on outputAlbedo in package/Shaders/Lighting.hlsl.

[github-actions]

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