feat: exponential height fog

[jiayev]

light-weighted exponential height fog, perf-friendly
supports per-weather settings

This pull request introduces a new Exponential Height Fog feature to the rendering pipeline, adding physically-based volumetric fog with support for dynamic cubemaps and directional inscattering. The implementation is modular and can be toggled via shader defines, with integration across multiple shader passes including lighting, water, effects, grass, and SSAO composite. It also updates the shared data structures to support the new fog parameters and ensures correct blending with existing fog and lighting logic.

Exponential Height Fog Feature Implementation:

• Added a new ExponentialHeightFog.hlsli shader, providing functions for exponential height fog computation and sunlight attenuation, with optional dynamic cubemap support.
• Introduced the ExponentialHeightFogSettings struct in SharedData.hlsli, and extended the global feature data buffer to include all relevant fog parameters. [1] [2]
• Created an .ini file to version the Exponential Height Fog feature.

Shader Integration and Usage:

• Integrated the exponential height fog logic into the main passes of Lighting.hlsl, Water.hlsl, Effect.hlsl, DistantTree.hlsl, RunGrass.hlsl, and ISSAOComposite.hlsl. This includes:
  • Applying fog color and attenuation to direct and indirect lighting. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
  • Ensuring correct blending with existing fog logic and IBL. [1] [2] [3]
  • Supporting toggling via the EXP_HEIGHT_FOG define and using appropriate samplers. [1] [2] [3] [4] [5] [6]

Dynamic Cubemaps Compatibility:

• Wrapped the contents of DynamicCubemaps.hlsli in an include guard to prevent multiple inclusion, and enabled optional use from within the new fog shader. [1] [2]

API and Function Signature Updates:

• Modified function signatures (e.g., GetSunColor) to accept world position for fog attenuation, ensuring correct application in water rendering. [1] [2] [3]

These changes collectively add a robust, configurable exponential height fog system with support for advanced lighting and environmental effects.

Summary by CodeRabbit

• New Features

  • Added configurable Exponential Height Fog (density, height, falloff, start distance, inscattering tint, dynamic cubemap support and mip control).
  • Integrated height fog into lighting, water, grass, distant objects and post-processing for improved sunlight attenuation and more natural scene blending.
  • UI controls, save/load persistence, and weather-variable hooks for runtime tuning.

• Chores

  • Minor stability/compatibility improvements.

[coderabbitai]

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📝 Walkthrough

Walkthrough

Adds a new Exponential Height Fog feature with C++ feature code, settings, UI, weather-variable registration, SharedData cbuffer fields, a shader header implementing fog and sunlight attenuation, shader integrations across multiple rendering passes, an INI, and include guards added to DynamicCubemaps.hlsli.

Changes

Cohort / File(s)	Summary
Shader Fog Definitions features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli, features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli	Adds GetExponentialHeightFog and GetSunlightFogAttenuation implementations; wraps DynamicCubemaps.hlsli in include guards.
Feature Implementation (C++) src/Features/ExponentialHeightFog.h, src/Features/ExponentialHeightFog.cpp	New ExponentialHeightFog Feature type with Settings, JSON load/save, ImGui UI, RestoreDefaultSettings, and RegisterWeatherVariables.
Global Registration & Buffers src/Globals.h, src/Globals.cpp, src/Feature.cpp, src/FeatureBuffer.cpp	Adds forward declaration, global instance exponentialHeightFog, registers feature in feature list, and appends settings to feature buffer data.
Shared Shader Data package/Shaders/Common/SharedData.hlsli	Adds ExponentialHeightFogSettings struct and exponentialHeightFogSettings field to the FeatureData cbuffer.
Shader Pipeline Integration package/Shaders/DistantTree.hlsl, package/Shaders/Effect.hlsl, package/Shaders/Lighting.hlsl, package/Shaders/RunGrass.hlsl, package/Shaders/ISSAOComposite.hlsl	Conditionally include ExponentialHeightFog header under EXP_HEIGHT_FOG and apply exponential-height fog and sunlight attenuation where enabled; adds sampler declaration in ISSAOComposite.
Water Shader Changes package/Shaders/Water.hlsl	Updates GetSunColor signature to include worldPosition and eyeIndex; integrates exponential height fog into sun color and fog composition paths, replacing prior fogAlpha usage with fogFactor in affected branches.
Feature Metadata features/Exponential Height Fog/Shaders/Features/ExponentialHeightFog.ini	Adds feature INI with Version = 1-0-0.

Sequence Diagram

sequenceDiagram
    participant Engine as Engine
    participant Feature as ExponentialHeightFog
    participant Weather as WeatherSystem
    participant Shared as SharedData(cbuffer)
    participant Shader as RenderingShaders

    Engine->>Feature: Instantiate / LoadSettings()
    Feature->>Weather: RegisterWeatherVariables()
    Feature->>Shared: Populate exponentialHeightFogSettings
    Shader->>Shared: Read exponentialHeightFogSettings
    alt exponentialHeightFogSettings.enabled
        Shader->>Shader: GetExponentialHeightFog(positionWS, cameraWS, fogColor)
        Shader->>Shader: GetSunlightFogAttenuation(positionWS, cameraWS)
        Shader->>Shader: Apply attenuation to lighting and fog blending
    else
        Shader->>Shader: Use existing fog paths
    end

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• fix: fog flicker in unified water #1772: Overlaps edits to package/Shaders/Water.hlsl fog computations — likely conflicting or complementary.
• feat(grass lighting): add complex grass detection threshold slider #1750: Related changes to package/Shaders/RunGrass.hlsl affecting grass lighting paths.
• feat: weather and imagespace editor #1630: Related integration with WeatherVariables/RegisterWeatherVariables API used by the new feature.

Suggested reviewers

• doodlum
• alandtse
• davo0411

Poem

🐇
I nibble mist at break of day,
shaders hum and colors play,
I hop through height and cubemap gleam,
tint the dawn and tweak the dream,
exponential fog — my fluffy scheme.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: exponential height fog' directly and concisely summarizes the main change in the pull request, which introduces a new exponential height fog feature system.

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✨ Finishing touches

🧪 Generate unit tests (beta)

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

---

No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

package/Shaders/Water.hlsl (1)

1303-1312: Clarify intent: PosAdjust[eyeIndex].w scaling is skipped when exponential height fog is active.

The else / #endif pattern here means that when exponentialHeightFogSettings.enabled is true, fogColor bypasses the PosAdjust[eyeIndex].w scaling. This appears intentional (the exponential fog function presumably returns a ready-to-use color), but it's a subtle control flow that could confuse future readers. A brief comment would help.

Note: the same pattern is used in the non-VC path (lines 1343–1352), so it's at least consistent.

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[github-actions]

Using provided base ref: ae827b8
Using base ref: ae827b8
Base commit date: 2026-02-12T11:15:29+10:00 (Thursday, February 12, 2026 11:15 AM)
No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In @features/Exponential Height
Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli:
- Around line 47-54: The dynamic cubemap branch is overwriting fogColor and
pre-multiplying by the fog factor, causing the fog attenuation to be applied
twice (once here and again when the shader returns alpha = 1.0f - expFogFactor);
update the block that runs when
SharedData::exponentialHeightFogSettings.useDynamicCubemaps > 0 so that fogColor
is set to tintColor * cubemapColor (do not multiply by (1.0f - expFogFactor)),
preserving expFogFactor usage only in the alpha/attenuation output; look for
SharedData::exponentialHeightFogSettings,
DynamicCubemaps::EnvReflectionsTexture.SampleLevel, fogColor and expFogFactor to
make this change.

🧹 Nitpick comments (4)

src/Features/ExponentialHeightFog.h (1)

8-8: Placeholder mod link needs updating before release.

The Nexus mod URL uses a placeholder ID 999999. This should be updated to the actual mod page URL once the feature is published, or consider returning an empty string if no mod page exists yet.

features/Exponential Height Fog/Shaders/Features/ExponentialHeightFog.ini (1)

1-2: Consider adding a trailing newline.

The file is missing a trailing newline. While INI parsers typically handle this, adding one ensures POSIX text file compliance and avoids potential issues with some tools.

📝 Suggested fix

 [Info]
 Version = 1-0-0
+

package/Shaders/Water.hlsl (1)

1039-1059: Consider VR compatibility for eye index.

The GetSunlightFogAttenuation call uses hardcoded FrameBuffer::CameraPosAdjust[0].xyz rather than passing the eye index from the caller. In VR, each eye has different camera positions. While this may have minimal visual impact for fog attenuation, consider whether the function should accept eyeIndex to maintain consistency with other water shader calculations.

src/Features/ExponentialHeightFog.cpp (1)

33-45: Potential UB: Casting uint32_t* to bool* for ImGui::Checkbox.

Lines 35 and 42 cast uint32_t settings members to bool*. While this works in practice, it's technically undefined behavior in C++ and could cause issues on platforms where sizeof(bool) != sizeof(uint32_t). ImGui's Checkbox expects a bool*, but the settings struct uses uint32_t for alignment.

Consider using a local bool variable and copying back, or using the uint32_t overload pattern:

Suggested pattern

-	ImGui::Checkbox("Enable Exponential Height Fog", (bool*)&settings.enabled);
+	bool enabledBool = settings.enabled != 0;
+	if (ImGui::Checkbox("Enable Exponential Height Fog", &enabledBool))
+		settings.enabled = enabledBool ? 1 : 0;

Also, line 44 uses ImGui::SliderFloat directly instead of Util::WeatherUI::SliderFloat, which may be intentional if this setting shouldn't be weather-variable-controllable, but it's inconsistent with the other sliders.

📜 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 f8aa7a2 and 8073566.

📒 Files selected for processing (16)

• features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli
• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• features/Exponential Height Fog/Shaders/Features/ExponentialHeightFog.ini
• package/Shaders/Common/SharedData.hlsli
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl
• package/Shaders/ISSAOComposite.hlsl
• package/Shaders/Lighting.hlsl
• package/Shaders/RunGrass.hlsl
• package/Shaders/Water.hlsl
• src/Feature.cpp
• src/FeatureBuffer.cpp
• src/Features/ExponentialHeightFog.cpp
• src/Features/ExponentialHeightFog.h
• src/Globals.cpp
• src/Globals.h

🧰 Additional context used

📓 Path-based instructions (4)

**/*.{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:

• src/Globals.h
• src/FeatureBuffer.cpp
• src/Feature.cpp
• package/Shaders/Water.hlsl
• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• package/Shaders/ISSAOComposite.hlsl
• src/Globals.cpp
• src/Features/ExponentialHeightFog.cpp
• features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli
• package/Shaders/Common/SharedData.hlsli
• src/Features/ExponentialHeightFog.h
• package/Shaders/Lighting.hlsl
• package/Shaders/RunGrass.hlsl
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl

src/**/*.{cpp,cxx,cc,h,hpp,hxx}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

src/**/*.{cpp,cxx,cc,h,hpp,hxx}: Ensure SE/AE/VR runtime compatibility; use runtime detection patterns (e.g., REL::RelocateMember())
Include robust error handling and resource management with graceful degradation in the plugin code

Files:

• src/Globals.h
• src/FeatureBuffer.cpp
• src/Feature.cpp
• src/Globals.cpp
• src/Features/ExponentialHeightFog.cpp
• src/Features/ExponentialHeightFog.h

**/*

⚙️ CodeRabbit configuration file

**/*: When reviewing PRs, please provide suggestions for:

1. Conventional Commit Titles (if not following https://www.conventionalcommits.org/ or
   if the existing title does not describe the code changes):
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   Style: lowercase description, no ending period
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   • docs: update shader documentation

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Files:

• src/Globals.h
• src/FeatureBuffer.cpp
• src/Feature.cpp
• package/Shaders/Water.hlsl
• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• package/Shaders/ISSAOComposite.hlsl
• src/Globals.cpp
• src/Features/ExponentialHeightFog.cpp
• features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli
• package/Shaders/Common/SharedData.hlsli
• src/Features/ExponentialHeightFog.h
• package/Shaders/Lighting.hlsl
• features/Exponential Height Fog/Shaders/Features/ExponentialHeightFog.ini
• package/Shaders/RunGrass.hlsl
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl

features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh}: Place all feature shaders under features/YourFeature/Shaders/
Avoid GPU register/buffer conflicts in HLSL; verify register usage (e.g., with hlslkit buffer scanning)

Files:

• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli

🧠 Learnings (11)

📓 Common learnings

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 0
File: :0-0
Timestamp: 2025-06-24T07:17:36.604Z
Learning: When reviewing PRs, always clarify the scope if there are multiple related features or dependencies. WeatherPicker was a separate PR that was already merged, while this PR focuses specifically on WetnessEffects climate preset system enhancements.

📚 Learning: 2025-08-17T18:37:35.839Z

Learnt from: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/**/*.{cpp,cxx,cc,h,hpp,hxx} : Register new features in the globals::features namespace

Applied to files:

• src/Globals.h
• src/FeatureBuffer.cpp
• src/Feature.cpp
• src/Globals.cpp
• src/Features/ExponentialHeightFog.cpp
• src/Features/ExponentialHeightFog.h

📚 Learning: 2025-08-17T18:37:35.839Z

Learnt from: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/**/*.{cpp,cxx,cc,h,hpp,hxx} : Feature classes must inherit from Feature (src/Feature.h) and implement DrawSettings(), LoadSettings(), and SaveSettings()

Applied to files:

• src/FeatureBuffer.cpp
• src/Feature.cpp
• src/Features/ExponentialHeightFog.cpp
• src/Features/ExponentialHeightFog.h

📚 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:

• src/FeatureBuffer.cpp
• package/Shaders/Water.hlsl
• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• package/Shaders/ISSAOComposite.hlsl
• features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli
• package/Shaders/Common/SharedData.hlsli
• package/Shaders/Lighting.hlsl
• package/Shaders/RunGrass.hlsl
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl

📚 Learning: 2025-06-17T09:27:49.594Z

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 1157
File: src/Feature.cpp:42-49
Timestamp: 2025-06-17T09:27:49.594Z
Learning: In src/Feature.cpp, when an obsolete feature's INI file is deleted, the feature should be silently disabled without surfacing any issues to the user. This is the intended behavior because a deleted INI file for an obsolete feature indicates that the user has properly cleaned up the obsolete feature.

Applied to files:

• src/Feature.cpp

📚 Learning: 2025-07-01T18:01:07.079Z

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 0
File: :0-0
Timestamp: 2025-07-01T18:01:07.079Z
Learning: In the skyrim-community-shaders project, simple scalar constants in HLSL shaders use #define (e.g., #define NTHREADS 128), while more complex constants use static const within namespaces (e.g., Math namespace in Math.hlsli). For epsilon standardization, #define is the appropriate choice since epsilon values are simple scalar constants.

Applied to files:

• features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli
• package/Shaders/Effect.hlsl

📚 Learning: 2025-06-17T05:40:22.785Z

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 577
File: features/Wetness Effects/Shaders/WetnessEffects/WetnessEffects.hlsli:57-61
Timestamp: 2025-06-17T05:40:22.785Z
Learning: Default parameter values are supported in the HLSL compiler used by the skyrim-community-shaders project, contrary to standard HLSL (FXC/DXC) limitations.

Applied to files:

• package/Shaders/ISSAOComposite.hlsl
• package/Shaders/Common/SharedData.hlsli
• package/Shaders/Lighting.hlsl
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl

📚 Learning: 2025-08-17T18:37:35.839Z

Learnt from: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh} : Avoid GPU register/buffer conflicts in HLSL; verify register usage (e.g., with hlslkit buffer scanning)

Applied to files:

• package/Shaders/ISSAOComposite.hlsl
• package/Shaders/DistantTree.hlsl
• package/Shaders/Effect.hlsl

📚 Learning: 2025-07-18T15:21:03.641Z

Learnt from: jiayev
Repo: doodlum/skyrim-community-shaders PR: 0
File: :0-0
Timestamp: 2025-07-18T15:21:03.641Z
Learning: In the skyrim-community-shaders rendering pipeline, materials with alpha < 1 or alpha blending enabled are rendered in non-deferred mode rather than deferred mode. This means issues with dynamic cubemaps on transparent materials are actually non-deferred rendering issues.

Applied to files:

• package/Shaders/Lighting.hlsl

📚 Learning: 2025-08-05T17:40:44.828Z

Learnt from: ThePagi
Repo: doodlum/skyrim-community-shaders PR: 1369
File: package/Shaders/Lighting.hlsl:0-0
Timestamp: 2025-08-05T17:40:44.828Z
Learning: In the skyrim-community-shaders repository, ultra trees (object LOD trees) are detected using a compound shader define condition `defined(DO_ALPHA_TEST) && defined(LOD_BLENDING) && defined(RIM_LIGHTING) && defined(SOFT_LIGHTING)` because "they have no define" according to the comment. The `ExtraFlags::IsTree` flag is used for different tree handling (AO removal in skylighting) and may not apply to ultra trees specifically. Before replacing the compound condition with `IsTree`, verification is needed to ensure the flag covers ultra trees.

Applied to files:

• package/Shaders/DistantTree.hlsl

📚 Learning: 2025-08-17T18:37:35.839Z

Learnt from: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh} : Place all feature shaders under features/YourFeature/Shaders/

Applied to files:

• package/Shaders/DistantTree.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). (4)

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

🔇 Additional comments (33)

features/Dynamic Cubemaps/Shaders/DynamicCubemaps/DynamicCubemaps.hlsli (1)

1-2: LGTM!

Include guards correctly added using the standard #ifndef/#define pattern with an appropriately named macro matching the filename.

src/Feature.cpp (2)

7-7: LGTM!

Include added in the correct alphabetical position among the feature includes.

---

237-238: LGTM!

Feature correctly registered in the static feature list using the globals::features namespace pattern. Based on learnings, this follows the required convention for feature registration.

src/FeatureBuffer.cpp (2)

5-5: LGTM!

Include added in correct alphabetical position.

---

53-54: Verify buffer order matches shader-side FeatureData struct.

The exponential height fog settings are appended after linearLighting. Ensure this order matches the FeatureData struct layout in SharedData.hlsli to prevent buffer misalignment issues. This is critical for HLSL constant buffer compatibility and 16-byte alignment requirements.

src/Features/ExponentialHeightFog.h (1)

34-47: Settings struct layout is correct.

The struct is properly aligned at 16 bytes for GPU buffer compatibility. The shader-side ExponentialHeightFogSettings in package/Shaders/Common/SharedData.hlsli matches the C++ definition exactly in field order and types. The padding ensures the total size is 64 bytes (4 × 16), which is correct for HLSL constant buffer alignment.

src/Globals.h (1)

33-33: LGTM! Feature registration follows established patterns.

The forward declaration and extern declaration for ExponentialHeightFog correctly follow the existing conventions used by other features in this codebase. Based on learnings, registering new features in the globals::features namespace is the expected pattern.

Also applies to: 88-88

src/Globals.cpp (1)

6-6: LGTM! Feature instance properly defined.

The include and global instance definition follow the established patterns for feature registration. The alphabetical ordering of includes is maintained, and the instance uses consistent default initialization.

Also applies to: 84-84

package/Shaders/RunGrass.hlsl (2)

457-459: LGTM! Conditional include properly guarded.

The ExponentialHeightFog include is correctly guarded by the EXP_HEIGHT_FOG define, following the pattern used for other optional features in this shader.

---

593-597: This architectural difference is intentional and appropriate.

The shader has two distinct implementations: the GRASS_LIGHTING path (lines ~465-838) is a full-featured PBR deferred rendering implementation that includes exponential height fog attenuation on directional lighting (lines 593-597), while the #else branch (lines 839+) is a simpler fallback without fog effects. The fog is only applied in the advanced lighting path, which is a reasonable design choice reflecting different quality tiers for different shader permutations.

package/Shaders/Common/SharedData.hlsli (2)

268-268: LGTM! Feature data addition follows existing pattern.

The exponentialHeightFogSettings is correctly added to the FeatureData constant buffer, maintaining the existing order of feature settings.

---

237-250: LGTM! Struct is properly aligned.

The ExponentialHeightFogSettings struct is correctly aligned to 16-byte boundaries (64 bytes total), which is required for constant buffer packing. The use of uint for boolean fields and padding for alignment follows HLSL conventions. The C++ Settings struct in ExponentialHeightFog.h matches the HLSL layout exactly, with equivalent field ordering and alignment.

package/Shaders/DistantTree.hlsl (2)

245-249: LGTM! Fog attenuation applied consistently in both render paths.

Both the DEFERRED and non-DEFERRED paths apply GetSunlightFogAttenuation to diffuseColor with proper enabled checks and matching parameter usage.

Also applies to: 286-290

---

182-185: Fix undefined sampler reference: SampShadowMaskSampler does not exist in this shader.

The code defines SampColorSampler as SampShadowMaskSampler at line 183, but SampShadowMaskSampler is not declared in DistantTree.hlsl. Only SampDiffuse (at register s0) is available. This will cause a compilation error if both EXP_HEIGHT_FOG and DYNAMIC_CUBEMAPS are defined together, since ExponentialHeightFog.hlsli uses SampColorSampler for cubemap sampling. Change the define to reference an existing sampler:

#define SampColorSampler SampDiffuse

⛔ Skipped due to learnings

Learnt from: ThePagi
Repo: doodlum/skyrim-community-shaders PR: 1369
File: package/Shaders/Lighting.hlsl:0-0
Timestamp: 2025-08-05T17:40:44.828Z
Learning: In the skyrim-community-shaders repository, ultra trees (object LOD trees) are detected using a compound shader define condition `defined(DO_ALPHA_TEST) && defined(LOD_BLENDING) && defined(RIM_LIGHTING) && defined(SOFT_LIGHTING)` because "they have no define" according to the comment. The `ExtraFlags::IsTree` flag is used for different tree handling (AO removal in skylighting) and may not apply to ultra trees specifically. Before replacing the compound condition with `IsTree`, verification is needed to ensure the flag covers ultra trees.

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: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/*/Shaders/**/*.{hlsl,hlsli,fx,fxh} : Avoid GPU register/buffer conflicts in HLSL; verify register usage (e.g., with hlslkit buffer scanning)

Learnt from: ThePagi
Repo: doodlum/skyrim-community-shaders PR: 1369
File: src/Features/SnowCover.cpp:515-515
Timestamp: 2025-10-02T14:20:33.454Z
Learning: In the Community Shaders codebase (skyrim-community-shaders repository), hardcoded shader resource slot numbers are used directly in code rather than being defined as named constants. This is the established convention and should not be flagged as an issue.

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 577
File: features/Wetness Effects/Shaders/WetnessEffects/WetnessEffects.hlsli:57-61
Timestamp: 2025-06-17T05:40:22.785Z
Learning: Default parameter values are supported in the HLSL compiler used by the skyrim-community-shaders project, contrary to standard HLSL (FXC/DXC) limitations.

package/Shaders/Effect.hlsl (3)

533-536: LGTM! Sampler alias correctly defined.

SampColorSampler is correctly aliased to SampBaseSampler, which is properly declared at register(s0) in this shader.

---

560-565: LGTM! Directional light fog attenuation in lighting function.

The fog attenuation is correctly applied to dirLightColor within the GetLightingColor function when the EffectShadows flag is set, maintaining consistency with other shaders in this PR.

---

841-862: LGTM! Fog composition logic properly integrates exponential height fog.

The implementation correctly:

1. Computes exponential height fog when enabled
2. Overrides fogColor and fogFactor with the new values
3. Sets fogMul = 1 to disable vanilla fog multiplier
4. Preserves the existing ADDBLEND/MULTBLEND blending behavior

package/Shaders/ISSAOComposite.hlsl (2)

188-205: Depth-based fog applied to sky when exponential fog enabled.

The condition on line 198 depth < 0.999999 || SharedData::exponentialHeightFogSettings.enabled means exponential height fog will be applied even to sky pixels (depth ≈ 1.0). This could be intentional for atmospheric effects, but verify this is the desired behavior for the sky.

The world position reconstruction (lines 190-192) and fog calculation logic are correct.

Is it intentional that exponential height fog applies to sky pixels? The original vanilla fog skipped pixels where depth >= 0.999999.

---

133-136: Verify sampler binding for SampColorSampler at register(s9).

ISSAOComposite.hlsl declares SampColorSampler at register(s9) when EXP_HEIGHT_FOG is enabled. Unlike other shaders that alias SampColorSampler to existing samplers via #define, this creates a new sampler that requires explicit binding. The sampler is used in ExponentialHeightFog.hlsli to sample the dynamic cubemap when DYNAMIC_CUBEMAPS is enabled. Verify that the C++ rendering code properly binds a sampler to slot 9 for this variant, or ensure the binding is handled through the shader feature system.

package/Shaders/Lighting.hlsl (3)

941-943: LGTM!

The conditional include for the ExponentialHeightFog header follows the established pattern used by other feature includes in this file.

---

2394-2399: LGTM!

The sunlight fog attenuation is correctly applied to the directional light color before other multipliers, and properly guarded by the feature's enabled setting.

---

3019-3033: LGTM!

The fog application logic correctly updates both the fog color and factor when exponential height fog is enabled, while preserving the existing behavior otherwise. The integration with IBL fog color modification above is properly ordered.

package/Shaders/Water.hlsl (5)

419-421: LGTM!

The conditional include for ExponentialHeightFog follows the same guarded pattern used elsewhere.

---

1222-1222: LGTM!

The call site correctly passes input.WPosition.xyz as the new world position parameter.

---

1232-1249: LGTM!

The VC path correctly integrates exponential height fog, updating both fog color and factor while preserving legacy behavior in the else branch with the PosAdjust multiplier.

---

1262-1279: LGTM!

The non-VC path mirrors the VC path integration correctly, using the distinct preFogColor/preFogFactor naming convention.

---

1285-1289: Verify: Refraction fog is disabled rather than replaced.

When exponential height fog is enabled, fogFactor is set to 0, which disables the depth-based refraction fog entirely rather than replacing it with exponential fog. The comment "TODO fix water fog blend" in the PR description may relate to this. If the intent is to apply exponential fog to refractions as well, this would need the fog to be computed using the refracted depth/position.

features/Exponential Height Fog/Shaders/ExponentialHeightFog/ExponentialHeightFog.hlsli (3)

1-8: LGTM!

The include guard and conditional includes follow established patterns in the codebase.

---

59-65: Consider: Inscattering distance calculation may not align with main fog.

Line 62 calculates dirExponentialHeightLineIntegral using max(rayLength - SharedData::exponentialHeightFogSettings.startDistance, 0), but rayLength has already been adjusted by startDistance in the main fog calculation (lines 28-37). This means startDistance is effectively subtracted twice for inscattering when startDistance > 0.

Was the intent to use the original viewToPosLength for inscattering, or should line 62 just use rayLength?

---

71-100: LGTM with note on coordinate system.

The function correctly computes sunlight attenuation through fog. The positionWS.z + cameraWS.z calculation on line 80 accounts for the codebase's convention where world positions are camera-relative, so adding cameraWS.z yields the absolute world height. Returning 0.0 for downward-pointing lights (lines 94-96) is correct since sunlight below the horizon should be fully attenuated.

src/Features/ExponentialHeightFog.cpp (3)

5-16: LGTM!

The JSON serialization macro correctly lists all settings fields that need to be persisted.

---

18-31: LGTM!

The settings management methods follow the established pattern used by other features in the codebase.

---

47-104: LGTM!

Weather variable registration is comprehensive for the float settings that should vary per-weather. The exclusion of enabled, useDynamicCubemaps, and cubemapMipLevel from weather variables is appropriate since those are global configuration options rather than per-weather parameters.

[github-actions]

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

[davo0411]

check ai otherwise looks good

[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

package/Shaders/Water.hlsl (1)

1039-1058: GetSunColor needs eyeIndex parameter for correct VR fog attenuation.

The function uses FrameBuffer::CameraPosAdjust[0].xyz for exponential height fog attenuation, which hardcodes eye 0's camera position. This is inconsistent with other fog calculations in the same file (see ExponentialHeightFog::GetExponentialHeightFog calls) and with VR-aware functions like GetWaterDiffuseColor that take eyeIndex as a parameter.

Since eyeIndex is available at the call site, add it as a parameter to GetSunColor and propagate it through ExponentialHeightFog::GetSunlightFogAttenuation.

🧹 Nitpick comments (2)

package/Shaders/Water.hlsl (2)

1267-1278: Inconsistent PosAdjust handling between VC and non-VC paths.

In the non-VC path (here), preFogColor *= PosAdjust[eyeIndex].w is correctly placed in the else branch (line 1276), so it only applies when exponential fog is disabled.

However, in the VC path (lines 1238-1246), fogColor *= PosAdjust[eyeIndex].w is applied unconditionally before the exponential fog block, meaning the scaling is applied even when exponential fog is enabled (though it gets passed to GetExponentialHeightFog).

Consider aligning the VC path to match this pattern for consistency:

♻️ Suggested fix for VC path (lines 1233-1248)

 #						if defined(IBL)
 		if (SharedData::iblSettings.EnableDiffuseIBL && !SharedData::InInterior) {
 			fogColor = ImageBasedLighting::GetFogIBLColor(fogColor);
 		}
 #						endif
-		fogColor *= PosAdjust[eyeIndex].w;
 #						if defined(EXP_HEIGHT_FOG)
 		if (SharedData::exponentialHeightFogSettings.enabled)
 		{
 			float4 exponentialHeightFog = ExponentialHeightFog::GetExponentialHeightFog(input.WPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, fogColor);
 			fogColor = exponentialHeightFog.xyz;
 			fogFactor = exponentialHeightFog.w;
 		}
+		else
 #						endif
+		fogColor *= PosAdjust[eyeIndex].w;

---

1284-1288: Known limitation: refraction fog blending disabled when exponential fog is enabled.

Setting fogFactor = 0 here effectively disables the depth-based fog blending for water refractions. This means refractionColor at line 1294 won't blend with fogColor, potentially causing visual discontinuity at water edges.

The PR objectives mention a "TODO to fix water fog blend"—this appears to be that case. Consider adding an inline comment to document this limitation:

📝 Suggested documentation

 #						if defined(EXP_HEIGHT_FOG)
 	if (SharedData::exponentialHeightFogSettings.enabled) {
+		// TODO: Implement proper exponential fog blending for water refractions
 		fogFactor = 0;
 	}
 #						endif

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**/*.{cpp,cxx,cc,c,h,hpp,hxx,hlsl,hlsli,fx,fxh,py}

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Files:

• package/Shaders/Water.hlsl

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Files:

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🧠 Learnings (2)

📓 Common learnings

Learnt from: alandtse
Repo: doodlum/skyrim-community-shaders PR: 0
File: :0-0
Timestamp: 2025-06-24T07:17:36.604Z
Learning: When reviewing PRs, always clarify the scope if there are multiple related features or dependencies. WeatherPicker was a separate PR that was already merged, while this PR focuses specifically on WetnessEffects climate preset system enhancements.

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.

Learnt from: CR
Repo: doodlum/skyrim-community-shaders PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-08-17T18:37:35.839Z
Learning: Applies to features/**/*.{cpp,cxx,cc,h,hpp,hxx} : Register new features in the globals::features namespace

📚 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/Water.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). (4)

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• GitHub Check: Validate shader compilation (VR, .github/configs/shader-validation-vr.yaml)
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🔇 Additional comments (3)

package/Shaders/Water.hlsl (3)

419-421: LGTM!

The conditional include follows the established pattern used by other features like TERRAIN_SHADOWS, SKYLIGHTING, and CLOUD_SHADOWS.

---

1222-1222: LGTM!

The call site correctly provides input.WPosition.xyz as the world position parameter.

---

1232-1248: Verify: PosAdjust scaling applied before exponential fog overwrites fogColor.

In this VC path, fogColor *= PosAdjust[eyeIndex].w (line 1238) is applied before the exponential height fog block potentially replaces fogColor entirely. If the exponential fog is enabled, the PosAdjust scaling is passed into GetExponentialHeightFog but the output completely replaces fogColor.

Please confirm this is the intended behavior—that the exponential fog system handles its own intensity scaling internally and doesn't need the PosAdjust factor applied to the final result.

_{✏️ Tip: You can disable this entire section by setting review_details to false in your review settings.}

[SkrubbySkrubInAShrub]

Tested this build:

• Compiled fine.
• no perf impact that I could notice
• no obvious artifacts
• all sliders do something
• works with weather editor.

[doodlum]

check ai, finish todo

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@package/Shaders/Water.hlsl`:
- Around line 1342-1359: The dangling else before the `#endif` causes the lerp
blend into finalColorPreFog to be skipped when EXP_HEIGHT_FOG is enabled; to
fix, remove the stray "else" so that after checking
SharedData::exponentialHeightFogSettings.enabled and (when true) updating
preFogColor and fogDistanceFactor via
ExponentialHeightFog::GetExponentialHeightFog, the finalColorPreFog =
lerp(finalColorPreFog, preFogColor * PosAdjust[eyeIndex].w, fogDistanceFactor)
always runs; adjust the conditional block around
ExponentialHeightFog::GetExponentialHeightFog/SharedData::exponentialHeightFogSettings.enabled
to not include an else that prevents the lerp.

🧹 Nitpick comments (1)

package/Shaders/Water.hlsl (1)

1286-1321: Please validate visual/perf impact for the new fog blend path.

This adds an extra fog evaluation in the main water color path; worth confirming cost and visual stability in heavy weather scenes.

As per coding guidelines: Always consider GPU workload and user experience when implementing graphics features.

[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

package/Shaders/Water.hlsl (1)

1304-1362: ⚠️ Potential issue | 🔴 Critical

Apply post-FogAlpha transformation and PosAdjust scaling to exponential height fog factor for consistency.

When EXP_HEIGHT_FOG is enabled, fogDistanceFactor is replaced with exponentialHeightFog.w without passing through Color::FogAlpha(), and fogColor/preFogColor skip the PosAdjust[eyeIndex].w scaling (which is only in the else block). This creates an inconsistent lerp: the standard fog path applies both gamma correction and PosAdjust scaling, while the exponential height fog path applies neither. Either apply the same transformations to the exponential height fog path, or verify that exponentialHeightFog.w and the color already account for these adjustments internally.

[davo0411]

@jiayev fix conflicts pls, @doodlum approve it

requested changes were completed. I have reviewed. AI comments fixed.