chore: "fix(pbr): metal low-light rendering fixed, improved cubemaps"

[doodlum]

Reverts #1404

Summary by CodeRabbit

• Bug Fixes
  • Improved specular reflections and roughness response for more consistent, physically plausible highlights across materials.
  • Removed unintended ambient specular boost in deferred/non-PBR rendering, reducing over-bright or washed-out highlights.
• Refactor
  • Streamlined specular evaluation logic (reflectance gating and view-direction handling) for more predictable lighting results and better alignment across rendering paths.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Updates shader logic affecting specular reflections: DeferredCompositeCS.hlsl changes reflectance gating, view vector computation, and roughness-to-level mapping; Lighting.hlsl removes an ambient directional specular addition in the non-PBR path. No public interfaces changed.

Changes

Cohort / File(s)	Summary of Changes
Specular gating, view vector, and roughness mapping package/Shaders/DeferredCompositeCS.hlsl	Replaced luminance threshold with per-channel non-zero reflectance check; V now uses normalize(positionWS.xyz); simplified roughness mapping to roughness = 1 - glossiness and level = roughness * 7.0.
Deferred lighting ambient specular adjustment package/Shaders/Lighting.hlsl	Removed addition of indirect directional ambient to specularColorPBR in non-PBR branch; retained diffuse vertexColor modulation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• fix(pbr): metal low-light rendering fixed, improved cubemaps #1404 — Modifies the same shader code paths (DeferredCompositeCS.hlsl specular logic and Lighting.hlsl PS_OUTPUT handling).
• revert(PBR): revert pbr refactor #1222 — Adjusts PBR-related lighting logic in Lighting.hlsl affecting specular/ambient handling.
• fix: fix hair specular #1328 — Edits pixel shader specular computation in Lighting.hlsl, changing ambient/specular application.

Suggested reviewers

• jiayev

Poem

A bunny peers at specular light,
Tweaks V’s glance to catch it right.
Roughness slides—so smooth, so clean,
No ambient hitch in the deferred scene.
With whiskers twitching, code hops through—
Reflections truer, shaders new. 🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between bd57c65 and 6f656e6.

📒 Files selected for processing (2)

• package/Shaders/DeferredCompositeCS.hlsl (1 hunks)
• package/Shaders/Lighting.hlsl (0 hunks)

✨ Finishing Touches

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch revert-1404-dev-16-08-2025

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[github-actions]

Using provided base ref: bd57c65
Using base ref: bd57c65
Base commit date: 2025-08-17T19:32:46+01:00 (Sunday, August 17, 2025 07:32 PM)
No actionable suggestions for changed features.

[github-actions]

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