fix(grass): no screen space shadow on back faces

[jiayev]

Summary by CodeRabbit

• Bug Fixes
  • Improved grass shadow rendering accuracy by refining how screen-space shadows are applied based on directional lighting angle and environmental location, enhancing visual realism in outdoor scenes.

[coderabbitai]

📝 Walkthrough

Walkthrough

The grass pixel shader's screen-space shadow calculation is now guarded by an additional check: the directional light angle must be non-negative. This prevents shadow application when the fragment is backlit, refining the existing interior-space check.

Changes

Grass Shader Screen-Space Shadow Guard

Layer / File(s)	Summary
Screen-space shadow directional light angle check package/Shaders/RunGrass.hlsl	The conditional gating screen-space shadow application now requires both !SharedData::InInterior and dirLightAngle >= 0.0, tightening when shadows are applied to the grass directional lighting calculation.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• community-shaders/skyrim-community-shaders#2344: Applies the same screen-space shadow guard pattern (!SharedData::InInterior and dirLightAngle >= 0.0) to Lighting.hlsl.
• community-shaders/skyrim-community-shaders#2198: Previous modification to RunGrass.hlsl shadow handling around dirDetailedShadow and screen-space shadow gating.
• community-shaders/skyrim-community-shaders#1456: Earlier changes to RunGrass.hlsl directional lighting logic involving dirLightAngle and shadow calculations.

Suggested reviewers

• doodlum
• alandtse

Poem

🐰 A shader tweak, so light and clean,
No inner glow from unseen gleam,
When angles wane below the shore,
The grass needs shadows less, not more! ✨

🚥 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 describes the main change: applying screen-space shadow only when the directional light angle is >= 0.0, which prevents shadows on back-facing surfaces.
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 fix-grass-shadow

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[github-actions]

No actionable suggestions for changed features.

[coderabbitai]

🧹 Nitpick comments (1)

package/Shaders/RunGrass.hlsl (1)

609-609: PR follows conventional commit format correctly.

The title fix(grass): no screen space shadow on back faces properly follows the conventional commits specification. If this change addresses a specific reported issue or feature request, consider adding an issue reference (e.g., "Fixes #XXXX" or "Closes #XXXX") to the PR description for better traceability. As per coding guidelines, appropriate GitHub keywords help link PRs to issues.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@package/Shaders/RunGrass.hlsl` at line 609, The PR title is fine but the
PR/commit body should include an issue reference for traceability; update the PR
description (or amend the commit message that introduced the change around the
conditional in RunGrass.hlsl — the if statement using SharedData::InInterior and
dirLightAngle) to include a GitHub keyword like "Fixes #<issue-number>" or
"Closes #<issue-number>" that points to the related bug/feature so the change is
automatically linked and closed by the PR.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@package/Shaders/RunGrass.hlsl`:
- Line 609: The PR title is fine but the PR/commit body should include an issue
reference for traceability; update the PR description (or amend the commit
message that introduced the change around the conditional in RunGrass.hlsl — the
if statement using SharedData::InInterior and dirLightAngle) to include a GitHub
keyword like "Fixes #<issue-number>" or "Closes #<issue-number>" that points to
the related bug/feature so the change is automatically linked and closed by the
PR.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 4f094cae-2cc3-4d89-b9bd-01de421bd3b2

📥 Commits

Reviewing files that changed from the base of the PR and between 8c9b18c and dd96ce9.

📒 Files selected for processing (1)

• package/Shaders/RunGrass.hlsl