fix(terrain shadows): fix compiler warnings

[doodlum]

Summary by CodeRabbit

• Performance & Optimization
  • Streamlined terrain shadow computation logic to reduce branching and improve rendering efficiency. Terrain shadows now disable cleanly without unnecessary calculations, resulting in faster execution when disabled.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The GetTerrainShadow function is reworked to add an early-return path when terrain shadows are disabled, and to simplify the enabled path by removing branching logic and unifying shadow computation into a single inline calculation.

Changes

Cohort / File(s)	Summary
Terrain Shadow Computation Simplification features/Terrain Shadows/Shaders/TerrainShadows/TerrainShadows.hlsli	Refactored GetTerrainShadow to return 1.0 immediately when disabled, removed DEFERRED/shader-variant branching in enabled path, and unified shadowFraction computation using inline GetTerrainShadowUV and simplified saturate formula. Eliminated intermediate terraOccUV variable and conditional shadow type logic.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• chore(terrain shadows): modernize #1678: Both PRs directly modify GetTerrainShadow in TerrainShadows.hlsli with the main PR removing DEFERRED branching while the related PR adds it for sharp vs blurry shadow variants.
• fix(terrain shadows): fix brightened lods #1547: Both PRs affect GetTerrainShadow's value generation and usage, with the main PR simplifying internal computation while the related PR removes interpolation of the returned value.

Suggested reviewers

• alandtse
• davo0411

Poem

🐰 Shadows cast by terrain's old design,
Now streamlined paths make logic align,
No branching waits, just numbers pure,
A swifter shade, forever sure! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title claims to fix compiler warnings, but the changes primarily refactor shadow computation logic by removing branching and simplifying calculations—no compiler warnings are mentioned in the summary.	Update the title to reflect the actual change, such as 'refactor(terrain shadows): simplify shadow computation and remove branching' or clarify what compiler warnings are addressed.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch terain-shadow-compile-pls

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[github-actions]

Using provided base ref: 72ba80e
Using base ref: 72ba80e
Base commit date: 2026-02-01T18:42:44Z (Sunday, February 01, 2026 06:42 PM)
No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@features/Terrain` Shadows/Shaders/TerrainShadows/TerrainShadows.hlsli:
- Around line 22-25: The code can divide by zero when shadowHeight.x equals
shadowHeight.y; in the terrain shadow computation (look for
SharedData::terraOccSettings.EnableTerrainShadow, GetTerrainZ,
ShadowHeightTexture.SampleLevel, GetTerrainShadowUV, and the final saturate call
using worldPos.z), add a small epsilon guard: compute the range as
(shadowHeight.x - shadowHeight.y), replace the division with worldPos.z minus
shadowHeight.y divided by max(range, epsilon) (or early-return a safe value like
1.0 when range is zero) so the saturate call never receives NaN.

🧹 Nitpick comments (1)

features/Terrain Shadows/Shaders/TerrainShadows/TerrainShadows.hlsli (1)

1-1: Conventional commit scope formatting + issue reference.

Current title uses a space in the scope. Consider: fix(terrain-shadows): fix compiler warnings (lowercase, no period, ≤50 chars). If this PR fixes a tracked bug, please add an issue reference in the description (e.g., Fixes #123 or `Closes `#123).

[coderabbitai]

⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🏁 Script executed:

find . -type f -name "*.hlsli" -o -name "*.hlsl" | head -20

Repository: doodlum/skyrim-community-shaders

Length of output: 1417

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🏁 Script executed:

find . -type f -path "*TerrainShadows*" | head -20

Repository: doodlum/skyrim-community-shaders

Length of output: 346

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🏁 Script executed:

find . -type f -name "*.hlsli" | xargs rg "GetTerrainZ" -A 5 -B 2

Repository: doodlum/skyrim-community-shaders

Length of output: 3742

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🏁 Script executed:

cat "./features/Terrain Shadows/Shaders/TerrainShadows/TerrainShadows.hlsli"

Repository: doodlum/skyrim-community-shaders

Length of output: 896

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🏁 Script executed:

rg "GetTerrainZ" -A 10 -B 2

Repository: doodlum/skyrim-community-shaders

Length of output: 2057

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🏁 Script executed:

rg "ZRange" -A 2 -B 2

Repository: doodlum/skyrim-community-shaders

Length of output: 4817

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rg "terraOccSettings" -l

Repository: doodlum/skyrim-community-shaders

Length of output: 184

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🏁 Script executed:

cat "src/Features/TerrainShadows.cpp" | head -100

Repository: doodlum/skyrim-community-shaders

Length of output: 3188

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cat "src/Features/TerrainShadows.h"

Repository: doodlum/skyrim-community-shaders

Length of output: 3178

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rg "max.*1e-5|max.*1e-6|max.*epsilon" -t hlsl -t hlsli

Repository: doodlum/skyrim-community-shaders

Length of output: 104

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rg "shadowHeight|ZRange.y - ZRange.x" -A 3 -B 1

Repository: doodlum/skyrim-community-shaders

Length of output: 3406

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🏁 Script executed:

cat "features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl" | grep -A 5 -B 5 "ZRange.y - ZRange.x"

Repository: doodlum/skyrim-community-shaders

Length of output: 545

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rg "divide.*zero|guard.*division|epsilon.*1e-" -i

Repository: doodlum/skyrim-community-shaders

Length of output: 1260

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🏁 Script executed:

grep -r "Math.hlsli\|EPSILON_DIVISION" "features/Terrain Shadows/Shaders/TerrainShadows/"

Repository: doodlum/skyrim-community-shaders

Length of output: 58

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🏁 Script executed:

cat "package/Shaders/Common/Math.hlsli" | grep -A 2 "EPSILON"

Repository: doodlum/skyrim-community-shaders

Length of output: 304

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Guard against a zero terrain shadow range.

If shadowHeight.x == shadowHeight.y, the division yields NaN and saturate won't recover. Add an epsilon guard to prevent division by zero.

🛡️ Suggested guard

-    float2 shadowHeight = GetTerrainZ(ShadowHeightTexture.SampleLevel(samp, GetTerrainShadowUV(worldPos.xy), 0));
-    return saturate((worldPos.z - shadowHeight.y) / (shadowHeight.x - shadowHeight.y));;
+    float2 shadowHeight = GetTerrainZ(ShadowHeightTexture.SampleLevel(samp, GetTerrainShadowUV(worldPos.xy), 0));
+    float denom = max(shadowHeight.x - shadowHeight.y, 1e-5);
+    return saturate((worldPos.z - shadowHeight.y) / denom);

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	if (!SharedData::terraOccSettings.EnableTerrainShadow)
	return 1.0;
	float2 shadowHeight = GetTerrainZ(ShadowHeightTexture.SampleLevel(samp, GetTerrainShadowUV(worldPos.xy), 0));
	return saturate((worldPos.z - shadowHeight.y) / (shadowHeight.x - shadowHeight.y));;
	if (!SharedData::terraOccSettings.EnableTerrainShadow)
	return 1.0;
	float2 shadowHeight = GetTerrainZ(ShadowHeightTexture.SampleLevel(samp, GetTerrainShadowUV(worldPos.xy), 0));
	float denom = max(shadowHeight.x - shadowHeight.y, 1e-5);
	return saturate((worldPos.z - shadowHeight.y) / denom);

🤖 Prompt for AI Agents

In `@features/Terrain` Shadows/Shaders/TerrainShadows/TerrainShadows.hlsli around
lines 22 - 25, The code can divide by zero when shadowHeight.x equals
shadowHeight.y; in the terrain shadow computation (look for
SharedData::terraOccSettings.EnableTerrainShadow, GetTerrainZ,
ShadowHeightTexture.SampleLevel, GetTerrainShadowUV, and the final saturate call
using worldPos.z), add a small epsilon guard: compute the range as
(shadowHeight.x - shadowHeight.y), replace the division with worldPos.z minus
shadowHeight.y divided by max(range, epsilon) (or early-return a safe value like
1.0 when range is zero) so the saturate call never receives NaN.

[github-actions]

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