feat: advanced skin

[jiayev]

This pull request introduces a new skin shading feature, adding both configuration and shader logic for advanced skin rendering. The main changes are the creation of a skin shader HLSL include file implementing subsurface scattering, dual specular lobes, fuzz, wetness, and detail normal blending, as well as a new configuration file for version tracking.

Skin shading feature implementation:

• Added new shader file Skin/Skin.hlsli containing a comprehensive namespace with functions for skin-specific lighting, subsurface scattering, dual specular GGX, fuzz, wetness, detail normal blending, and procedural noise for effects like sweat. This file leverages multiple shared shader utilities and implements techniques from recent rendering research.

Configuration and versioning:

• Introduced a new [Info] section with a version number in Skin/Shaders/Features/Skin.ini to track the feature's version.

Summary by CodeRabbit

• New Features
  • Advanced Skin rendering: configurable roughness, specular, subsurface scattering, fuzz, thickness, detail textures, and wetness normals
  • Dynamic wetness: combined water+sweat, procedural noise, per-geometry wetness with caching, and public runtime API for integration
  • New shader paths and skin parameter set exposed to shaders; runtime UI and settings for skin feature
• Bug Fixes
  • Corrected shader resource setup naming/wiring for reliable resource updates and binding

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 27c674e and 6662499.

📒 Files selected for processing (1)

• src/Features/Skin.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

• src/Features/Skin.cpp

---

📝 Walkthrough

Walkthrough

Adds an Advanced Skin feature: shader utilities (SSS, BRDF, normals, procedural wetness), lighting-path integration, a C++ Skin feature (settings, hooks, per-geometry wetness caching, extra texture derivation), a DynamicWetness public API header, and engine wiring/registering for runtime binding.

Changes

Skin Rendering Feature

Layer / File(s)	Summary
INI & shader include boilerplate features/Skin/Shaders/Features/Skin.ini, features/Skin/Shaders/Skin/Skin.hlsli	Adds feature INI and shader include/guard boilerplate for Skin and declares conditional per-geometry/texture bindings.
Shader core utilities & wetness features/Skin/Shaders/Skin/Skin.hlsli	Adds Skin namespace utilities: curvature, SSS transmittance, DualSpecularGGX, direct/indirect lighting helpers, normal reorientation/TBN, height→normal, FBM/Perlin noise, and GetWetness.
DynamicWetness public API include/DynamicWetness_PublicAPI.h	Adds SWE::API header to resolve DynamicWetness DLL exports, decode env state, and provide safe wrappers for wetness/env queries and external wetness setters.
Material properties & shared data package/Shaders/Common/LightingCommon.hlsli, package/Shaders/Common/SharedData.hlsli	Extends MaterialProperties with skin-only fields and adds SharedData::SkinData plus FeatureData.skinData for CPU-to-shader parameters.
Lighting evaluation integration package/Shaders/Common/LightingEval.hlsli	Adds SKIN/CS_SKIN guarded early-return branches in EvaluateLighting and GetIndirectLobeWeights to use Skin lighting lobe and direct-light paths when enabled.
Pixel shader skin effects package/Shaders/Lighting.hlsl	Adds CS_SKIN texture samplers and Skin include, samples extra/wetness textures, computes detail/wetness normals (height or direct), applies material overrides (roughness, secondary roughness, thickness, subsurface, fuzz, AO, curvature), integrates Skin::GetWetness into wetness accumulation, and applies wetness-based normal/gloss clamping.
Skin feature header src/Features/Skin.h	Declares Skin : Feature with Settings, SkinData/PerGeometryData layouts, ExtraTextures bookkeeping, hooks/thunks, and public lifecycle/resource methods.
Skin feature implementation src/Features/Skin.cpp	Implements settings (JSON + ImGui), skin detail texture loading, dynamic wetness init, per-actor wetness computation/caching (dynamic or stamina-based), extra texture derivation (_rfaos/_wet), material/geometry hook logic, per-geometry cbuffers, and SetShaderResources binding.
Feature registration & buffer wiring src/Feature.cpp, src/FeatureBuffer.cpp, src/Globals.h, src/Globals.cpp	Includes Skin header, registers globals::features::skin, and appends Skin common buffer data into the feature-buffer payload.
Engine integration & includes src/Hooks.cpp, src/State.cpp	Adds Skin includes and calls skin.SetShaderResources(context) from State::Draw (with Tracy instrumentation); corrects terrain helper call spelling.
Resource method name fixes src/Features/TerrainHelper.h/.cpp, src/TruePBR.h/.cpp	Renames SetShaderResouces → SetShaderResources across declarations and definitions to align callers and implementations.

sequenceDiagram
  participant GameEngine
  participant SkinFeature
  participant DynamicWetnessDLL
  participant PixelShader
  GameEngine->>SkinFeature: PostPostLoad / Install hooks
  SkinFeature->>DynamicWetnessDLL: Init() / Query wetness (GetFinalWetness)
  PixelShader->>SkinFeature: Request wetness / skin params (GetWetness)
  SkinFeature->>PixelShader: Bind SRVs + Per-geometry CB (SkinPerGeometry)
  PixelShader->>GameEngine: Render with modified material/wetness

Loading

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly Related PRs

• community-shaders/skyrim-community-shaders#1633: Lighting evaluation pipeline changes this PR extends with skin-specific branches.
• community-shaders/skyrim-community-shaders#1290: Refactors State::Draw/render flow and shader resource update batching relevant to SetShaderResources changes.
• community-shaders/skyrim-community-shaders#2210: TruePBR resource update/path changes that intersect with this PR's wiring and method renames.

Suggested Reviewers

• doodlum
• davo0411
• alandtse

Poem

🐇 I hop through normals, fractal dew and light,

I hum dual-GGX and smooth the SSSight.
I cache a droplet, bind a map with care,
I tweak a gloss, I nudge the fuzz — shaders sing in air.
Cheers from a rabbit, wetness tracked with flair.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 29.85% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: advanced skin' directly and clearly describes the main change—a new advanced skin shading feature with comprehensive shader implementation, configuration, and runtime support.
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)

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Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 OpenGrep (1.22.0)

OpenGrep fatal error (exit code 2): [00.14][ERROR]: Error: exception Unix_error: No such file or directory stat src/Features/Skin.cpp
Raised by primitive operation at UTmp.replace_named_pipe_by_regular_file_if_needed in file "libs/commons/UTmp.ml", line 145, characters 8-27
Called from Scan_CLI.replace_target_roots_by_regular_files_where_needed.(fun) in file "src/osemgrep/cli_scan/Scan_CLI.ml", lines 1086-1087, characters 19-65
Called from List_.fast_map in file "libs/commons/List_.ml", line 81, characters 17-20
Called from Scan_C

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[github-actions]

No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 7

🧹 Nitpick comments (1)

features/Skin/Shaders/Features/Skin.ini (1)

1-2: Suggested PR metadata polish

Consider updating the PR title to a stricter Conventional Commit form, e.g. feat(skin): add advanced skin shading, and add a description footer like Implements #2428 (or `Addresses `#2428) for auto-linking semantics.

As per coding guidelines, "When reviewing PRs, please provide suggestions for Conventional Commit Titles ... and Issue References ...".

🤖 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 `@features/Skin/Shaders/Features/Skin.ini` around lines 1 - 2, Update the PR
metadata to follow Conventional Commits by changing the PR title to a stricter
format such as "feat(skin): add advanced skin shading" and append an issue
reference footer like "Implements `#2428`" or "Addresses `#2428`" in the PR
description; this applies to the submission touching
Features/Skin/Shaders/Features/Skin.ini (see the [Info] Version entry) so the
commit/PR title and description include the conventional prefix and the issue
footer for auto-linking.

🤖 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.

Inline comments:
In `@features/Skin/Shaders/Skin/Skin.hlsli`:
- Around line 190-193: The quaternion computation for reorienting normals can
divide by zero when dot(s, t) ≈ -1; replace the single-line q = float4(...) /
sqrt(...) with a guarded computation: compute float d = dot(s,t); if (2*(d+1) is
below an epsilon) build a 180° quaternion by choosing an arbitrary axis
orthogonal to s (e.g., axis = normalize(cross(s, (abs(s.x) < 0.9) ?
float3(1,0,0) : float3(0,1,0))); q = float4(axis, 0)); otherwise compute q as
before using denom = sqrt(2*(d+1)) and the existing formula; keep the subsequent
rotation formula that uses q.w and q.xyz unchanged. This change should be
applied where q (and variables s, t, u) are computed/used in Skin.hlsli.
- Around line 165-166: The diffuse lobe calculation subtracts only specular.x
and specular.y from all color channels, which ignores the blue channel and can
go negative; change the line using the per-channel specular weights and clamp
the result: set lobeWeights.diffuse = material.BaseColor * saturate(1.0 -
lobeWeights.specular) (using HLSL saturate or max to ensure non-negative
components) so the subtraction is done component-wise against
lobeWeights.specular and cannot produce negative values.

In `@package/Shaders/Lighting.hlsl`:
- Around line 1900-1903: The fragment shader is calling
TexSkinExtraSampler.GetDimensions and TexSkinWetnessSampler.GetDimensions
per-pixel which is expensive; remove those runtime dimension queries and instead
source hasSkinExtra and hasSkinWetness from constant data or binding-time state
(e.g., a material/feature flag in the constant buffer) or by binding known
fallback textures so availability is known at draw time; update the shader to
stop using
TexSkinExtraSampler.GetDimensions/TexSkinWetnessSampler.GetDimensions, read
hasSkinExtra/hasSkinWetness from the provided constant (or sampler binding
presence), and ensure any code that sets these flags at draw/dispatch time is
adjusted to populate the constant buffer or bind the fallback textures
accordingly.

In `@src/Features/Skin.cpp`:
- Around line 318-339: The water-height lookup in the
get_nearest_water_object_height lambda (used to set waterHeight inside
GetWetness(), which is called from BSLightingShader_SetupGeometry()) iterates
waterManager->waterObjects and multiBounds per draw; move this work out of the
geometry hook by computing and caching the nearest water height once per actor
per frame (or during a prepass/update step) and reading the cached value in
GetWetness(); implement a per-frame cache keyed by the actor (or shader owner)
plus a frame counter to invalidate each frame, populate it from the
prepass/update function (or actor update hook) and replace the inline walk
inside get_nearest_water_object_height with a simple cached lookup, and apply
the same change to the similar code around the referenced 367-370 region.
- Around line 610-614: The thunk BSLightingShader_SetupGeometry::thunk currently
always calls into skin.BSLightingShader_SetupGeometry(Pass) and can dereference
a null PerGeometryCB if SetupResources hasn't run; guard this by checking the
skin feature is initialized and PerGeometryCB is non-null (e.g., a boolean like
skin.initialized or directly skin.PerGeometryCB) before calling
skin.BSLightingShader_SetupGeometry(Pass), and if the check fails simply call
and return func(This, Pass, RenderFlags) without touching PerGeometryCB;
reference the thunk BSLightingShader_SetupGeometry::thunk, the member
skin.BSLightingShader_SetupGeometry, the SetupResources-produced PerGeometryCB,
and the original func to implement the guard.
- Around line 390-403: The fade math uses 1.0f / settings.WetFadeTime which can
divide by zero; before any use (e.g., around the blocks updating
cached.x/cached.y/wetness.x/wetness.w) clamp or sanitize settings.WetFadeTime to
a safe minimum (e.g., replace with max(settings.WetFadeTime, 0.0001f) or compute
a local float wetFadeInv = settings.WetFadeTime > 0 ? 1.0f /
settings.WetFadeTime : 1.0f / 0.0001f) and use that local value in the
subtraction expressions so the code that updates cached and wetness never
performs 1.0f / 0.0f.

In `@src/Features/Skin.h`:
- Line 30: SupportsVR() currently returns true unconditionally while
BSLightingShader vfunc hooks are installed with fixed slots; change this so
SupportsVR() performs runtime variant detection and only returns true when VR
layout is detected, and update the hook installation to use REL::RelocateMember
(or equivalent runtime relocation) to resolve the BSLightingShader vfunc slots
per-variant before patching; specifically modify SupportsVR(), the
BSLightingShader hook setup code, and any installer that assumes fixed slots so
they use the runtime-detection pattern and REL::RelocateMember to select correct
vfunc indices for SE/AE/VR.

---

Nitpick comments:
In `@features/Skin/Shaders/Features/Skin.ini`:
- Around line 1-2: Update the PR metadata to follow Conventional Commits by
changing the PR title to a stricter format such as "feat(skin): add advanced
skin shading" and append an issue reference footer like "Implements `#2428`" or
"Addresses `#2428`" in the PR description; this applies to the submission touching
Features/Skin/Shaders/Features/Skin.ini (see the [Info] Version entry) so the
commit/PR title and description include the conventional prefix and the issue
footer for auto-linking.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: fa779de6-f973-4591-ada1-470ee0bfa216

📥 Commits

Reviewing files that changed from the base of the PR and between 35b6f05 and 50039fc.

⛔ Files ignored due to path filters (1)

• features/Skin/Shaders/Skin/skin_detail_n.dds is excluded by !**/*.dds

📒 Files selected for processing (19)

• features/Skin/Shaders/Features/Skin.ini
• features/Skin/Shaders/Skin/Skin.hlsli
• include/DynamicWetness_PublicAPI.h
• package/Shaders/Common/LightingCommon.hlsli
• package/Shaders/Common/LightingEval.hlsli
• package/Shaders/Common/SharedData.hlsli
• package/Shaders/Lighting.hlsl
• src/Feature.cpp
• src/FeatureBuffer.cpp
• src/Features/Skin.cpp
• src/Features/Skin.h
• src/Features/TerrainHelper.cpp
• src/Features/TerrainHelper.h
• src/Globals.cpp
• src/Globals.h
• src/Hooks.cpp
• src/State.cpp
• src/TruePBR.cpp
• src/TruePBR.h

[github-actions]

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

[davo0411]

looks good, please address AI

[SkrubbySkrubInAShrub]

Maybe good if someone else looked too, but code looks good and am sure it has been tested enough in all the pp builds.
Please do update the branch and resolve the AI comments.