fix(grass): use correct light direction

[jiayev]

This pull request makes a minor update to the RunGrass.hlsl shader to ensure the correct directional light vector is used in specular lighting calculations. The change clarifies which value is passed to the GrassLighting::GetLightSpecularInput function, improving code correctness and maintainability.

• Lighting calculation fix:
  • Updated the call to GrassLighting::GetLightSpecularInput to use SharedData::DirLightDirection.xyz instead of DirLightDirection, ensuring the correct directional light vector is provided for specular lighting.

Summary by CodeRabbit

• Bug Fixes
  • Fixed directional lighting for grass so specular highlights and shading match the scene light direction, improving visual consistency and realism.

[coderabbitai]

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Walkthrough

Switches the directional light vector source in the pixel shader call to GrassLighting::GetLightSpecularInput from DirLightDirection to SharedData::DirLightDirection.xyz in package/Shaders/RunGrass.hlsl; other arguments and control flow are unchanged.

Changes

Cohort / File(s)	Summary
Shader directional light data source package/Shaders/RunGrass.hlsl	Replaced the first argument of GrassLighting::GetLightSpecularInput in the pixel shader from DirLightDirection to SharedData::DirLightDirection.xyz; other parameters unchanged.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Suggested reviewers

• doodlum
• Pentalimbed

Poem

🐰 In blades of grass the sunlight plays,
A shared direction lights the days.
One small swap, the shimmer’s right,
Specular hops into the light. 🌿✨

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(grass): use correct light direction' directly matches the main change: switching from DirLightDirection to SharedData::DirLightDirection.xyz in the grass shader's specular lighting calculation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[github-actions]

Using provided base ref: 7a53214
Using base ref: 7a53214
Base commit date: 2025-11-16T19:03:02Z (Sunday, November 16, 2025 07:03 PM)
No actionable suggestions for changed features.

[doodlum]

its already world space

[coderabbitai]

Actionable comments posted: 1

📜 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 f727bd8 and 9fede19.

📒 Files selected for processing (1)

• package/Shaders/RunGrass.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/RunGrass.hlsl

🧠 Learnings (2)

📓 Common learnings

Learnt from: jiayev
Repo: doodlum/skyrim-community-shaders PR: 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.

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 0
File: :0-0
Timestamp: 2025-07-05T05:20:45.823Z
Learning: In the skyrim-community-shaders repository, file deletion error handling improvements that replace existence checks and try-catch blocks with std::filesystem::remove error-code-based approaches are considered bug fixes rather than refactoring, as they address inadequate error handling and misleading log messages.

📚 Learning: 2025-08-03T18:37:19.690Z

Learnt from: jiayev
Repo: doodlum/skyrim-community-shaders PR: 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/RunGrass.hlsl

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: Validate shader compilation (VR, .github/configs/shader-validation-vr.yaml)
• GitHub Check: Validate shader compilation (Flatrim, .github/configs/shader-validation.yaml)
• GitHub Check: Build plugin and addons

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

LGTM! Change aligns with existing usage patterns.

The change to use SharedData::DirLightDirection.xyz is consistent with line 584, which already uses SharedData::DirLightDirection.xyz for the directional light angle calculation in the same shader path.

However, please verify whether line 617 (in the TRUE_PBR path) should also be updated for consistency:

Line 617 passes DirLightDirection (from the constant buffer) to PBR::GetDirectLightInput. If SharedData::DirLightDirection is the canonical source, that call may need the same update.

---

🏁 Script executed:

#!/bin/bash
# Description: Check usage patterns of DirLightDirection vs SharedData::DirLightDirection in shader files

# Search for all DirLightDirection usages in HLSL files to identify inconsistent patterns
rg -n -C3 --type=hlsl 'DirLightDirection' -g '!RunGrass.hlsl'

# Also check in RunGrass.hlsl specifically
rg -n 'DirLightDirection' package/Shaders/RunGrass.hlsl

Length of output: 715

---

Update line 617 for consistency with GRASS_LIGHTING data sources.

The change at line 645 correctly aligns with line 584's usage of SharedData::DirLightDirection.xyz within the GRASS_LIGHTING path. However, line 617 in the TRUE_PBR sub-path still uses the constant buffer DirLightDirection directly.

For consistency within the GRASS_LIGHTING block, line 617 should also be updated to use SharedData::DirLightDirection:

PBR::GetDirectLightInput(dirDiffuseColor, coatDirDiffuseColor, dirTransmissionColor, dirSpecularColor, normal, normal, viewDirection, viewDirection, SharedData::DirLightDirection, SharedData::DirLightDirection, lightProperties, pbrSurfaceProperties, tbn, input.TexCoord.xy);

🤖 Prompt for AI Agents

In package/Shaders/RunGrass.hlsl around line 617, the TRUE_PBR path still passes
the standalone constant buffer DirLightDirection to PBR::GetDirectLightInput
while the GRASS_LIGHTING path uses SharedData::DirLightDirection; update the
PBR::GetDirectLightInput call to use SharedData::DirLightDirection for both
directional-light parameters (replacing DirLightDirection with
SharedData::DirLightDirection) so it matches the GRASS_LIGHTING data source and
remains consistent with the change at line 645.

[github-actions]

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