fix(wetness): reflection angle; clamp puddle roughness

[Copilot]

Puddles were hard to see from non-sun-facing angles even with Dynamic Cubemaps enabled.

Root Cause

Two issues in Lighting.hlsl:

1. Deferred GBuffer normal was lerped, not assigned directly. The deferred composite does a single cubemap lookup using whatever normal is in the GBuffer. Lerping screenSpaceNormal toward wetnessNormal by wetnessGlossinessSpecular produces a direction wrong for both contributions — the material's specular (wants the surface normal) and the water film reflection (wants the flat puddle normal). Since wetnessReflectance from GetWetnessIndirectLobeWeights already scales intensity by wetness amount, lerping the direction was double-counting the fade.

2. waterRoughnessSpecular could reach 0 for fully-wet puddles, creating a near-singular GGX retroreflection peak roughly 30–40× stronger when facing the sun than from any other angle. The ripple normal map adds micro-variation but the GGX distribution still peaks sharply at roughness=0.

Fix

Use wetnessNormal directly for the GBuffer normal and waterRoughnessSpecular directly for roughness when wetness is present. Water film reflects from its own surface — wetnessReflectance already encodes how much. Puddles only form on flat surfaces (gated by vertexNormal.z), so the material's residual specular in the combined reflectance sees negligible directional error.

Clamp waterRoughnessSpecular to a named constant wetnessMinPuddleRoughness = 0.05. Real rain water is kept rough by continuous ripple disturbance; 0.05 preserves a visually glossy appearance while distributing the specular lobe across a wider solid angle.

// Before
screenSpaceNormal = lerp(screenSpaceNormal, normalize(WorldToView(wetnessNormal)), wetnessGlossinessSpecular);
material.Roughness = lerp(material.Roughness, waterRoughnessSpecular, wetnessGlossinessSpecular);

waterRoughnessSpecular = saturate(1.0 - wetnessGlossinessSpecular);

// After
// Reflection is from the water film surface; wetnessReflectance scales intensity by wetness amount.
screenSpaceNormal = normalize(WorldToView(wetnessNormal));
material.Roughness = waterRoughnessSpecular;

static const float wetnessMinPuddleRoughness = 0.05;
waterRoughnessSpecular = max(saturate(1.0 - wetnessGlossinessSpecular), wetnessMinPuddleRoughness);

Summary by CodeRabbit

• Bug Fixes
  • Prevented wet puddles from producing unrealistically shiny highlights by enforcing a minimum roughness, yielding more consistent specular behavior.
  • Improved wetness rendering so puddle normals and surface roughness are applied consistently, resulting in more realistic and stable wet-surface visuals.

[github-actions]

No actionable suggestions for changed features.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

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Run ID: 94f71356-d838-4918-91d9-709c55f290a1

📥 Commits

Reviewing files that changed from the base of the PR and between 98f83a8 and 6830e65.

📒 Files selected for processing (1)

• package/Shaders/Lighting.hlsl

🚧 Files skipped from review as they are similar to previous changes (1)

• package/Shaders/Lighting.hlsl

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📝 Walkthrough

Walkthrough

Introduces a minimum puddle roughness constant (0.05) and clamps computed water specular roughness to that minimum; in the wetness branch the shader now overwrites the screen-space normal from the wetness normal and directly sets material.Roughness to the clamped value instead of blending.

Changes

Wetness Puddle Specularity

Layer / File(s)	Summary
Constant / Data package/Shaders/Lighting.hlsl	Adds wetnessMinPuddleRoughness = 0.05 and clamps waterRoughnessSpecular = max(saturate(1.0 - wetnessGlossinessSpecular), wetnessMinPuddleRoughness).
Core Wetness Logic package/Shaders/Lighting.hlsl	When waterRoughnessSpecular < 1, stop blending; set screenSpaceNormal = normalize(WorldToView(wetnessNormal...)) and material.Roughness = waterRoughnessSpecular directly (replaces previous lerp behavior).
Tests / Docs none changed	No test or documentation files modified in this diff.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• chore(wetness effects): wetness improvements and add fresnel #1468: Modifies wetness logic and waterRoughnessSpecular computation in the same Lighting.hlsl region.
• fix(wetness): fix water roughness and normal #1717: Changes application of wetness normals and roughness in the WETNESS_EFFECTS path in Lighting.hlsl.
• fix(pbr): clamp roughness at a bigger value #1351: Addresses minimum roughness behavior; related to puddle roughness clamping.

Suggested reviewers

• jiayev
• davo0411
• doodlum

Poem

🐰 A puddle once gleamed far too bright,
I nudged its shine down to polite,
With a tiny roughness floor,
The gloss won't dazzle anymore,
Now reflections hop into sight. 🥕✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes both main fixes in the changeset: correcting the reflection angle (screenSpaceNormal assignment) and clamping puddle roughness to a minimum of 0.05.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch copilot/fix-wetness-effect-issue

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