fix(lighting): guard EMAT parallax shadow against undefined TBN

[SkrubbySkrubInAShrub]

Summary

The EMAT parallax-shadow block in Lighting.hlsl reads the tangent-space basis tbn via mul(refractedLightDirection, tbn), but tbn is only defined under defined(SKINNED) || !defined(MODELSPACENORMALS). For MODELSPACENORMALS && !SKINNED permutations, the block read an undefined tbn, producing garbage parallax soft-shadow results.

This gates the block on the same condition that defines tbn, matching the idiom already used elsewhere in the file (e.g. the EMAT normal-mapping block and the tbn definition itself).

Change

package/Shaders/Lighting.hlsl — two lines: tighten #if defined(EMAT) → #if defined(EMAT) && (defined(SKINNED) || !defined(MODELSPACENORMALS)) around the parallax-shadow block (and annotate the matching #endif).

The guard only removes the block from permutations where tbn was undefined, so it cannot introduce a compile error — only fix the latent undefined read. CI shader validation covers the affected permutations.

Attribution

Ported from ParticleTroned/skyrim-community-shaders (fix(lighting): guard EMAT parallax shadow TBN use).

🤖 Generated with Claude Code

Cherrypicked from open shaders

Summary by CodeRabbit

• Bug Fixes
  • Adjusted parallax shadow rendering to activate only under specific rendering configurations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 3e6a9d82-2e12-49cf-adcf-f17841c8de61

📥 Commits

Reviewing files that changed from the base of the PR and between 8465329 and 86b2ce7.

📒 Files selected for processing (1)

• package/Shaders/Lighting.hlsl

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📝 Walkthrough

Walkthrough

This PR refines shader compilation by narrowing the conditional guard for EMAT parallax shadow logic in Lighting.hlsl. The block now compiles only when EMAT is defined and the shader uses skinning or does not rely on model-space normals.

Changes

EMAT parallax shadow conditional guard

Layer / File(s)	Summary
Narrow EMAT parallax shadow guard package/Shaders/Lighting.hlsl	The preprocessor condition at line 2908 changes from defined(EMAT) to defined(EMAT) && (defined(SKINNED) || !defined(MODELSPACENORMALS)), and the matching #endif at line 2938 is updated to close the narrowed block, preventing EMAT parallax shadow execution in certain shader variant combinations.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• community-shaders/skyrim-community-shaders#2240: Adjusts the same EMAT parallax shadow guard in Lighting.hlsl with the same compound preprocessor condition.
• community-shaders/skyrim-community-shaders#1545: Refactors EMAT parallax and shadow control flow in the same file, overlapping with this conditional guard refinement.

Suggested reviewers

• davo0411
• alandtse

Poem

🐰 A guard grows wise, with sharper sight,
Not all EMAT shades shall see the light.
When model-space normals dance alone,
This shadow stays in shadow's zone. ✨

🚥 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 reflects the main change: guarding an EMAT parallax shadow code block against undefined TBN (tangent-space basis), which is the core bug fix in the changeset.
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

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[github-actions]

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