fix(water): TAA water black edge line

[davo0411]

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR introduces height-aware wetness effects for water simulation by adding a new HLSL shader header with displacement-based cavity detection, gradient normal computation, and pool mask shaping logic, alongside C++ allocation of TAA water history render targets to store the computed effects.

Changes

Height-Aware Wetness Effects and TAA Water Rendering

Layer / File(s)	Summary
Displacement height sampling and cavity detection features/Wetness Effects/Shaders/WetnessEffects/WetnessEffectsHeight.hlsli	Introduces GetHeightAwareDistanceFade, SampleMeshDisplacementHeight, GetMeshHeightCavity, and terrain/mesh gradient normal functions using ddx/ddy neighborhood sampling to detect pooling cavities and compute height-gradient normals for tangent-space normal mapping.
Pool masks and puddle/raindrop effects features/Wetness Effects/Shaders/WetnessEffects/WetnessEffectsHeight.hlsli	Converts raw cavity and distance fade into a neutral/peak/depression pool mask via lerp(0.5, cavity, distanceFade), applies the mask to scale puddle intensity, and generates raindrop height placement from pool mask and flatness parameters.
Height gradient normal blending features/Wetness Effects/Shaders/WetnessEffects/WetnessEffectsHeight.hlsli	Blends incoming wetness normals toward height-gradient normals scaled by wetnessPuddleDepth * distanceFade * 0.65, with early-exit for minimal depths; closes shader header guards.
TAA water history render targets src/Deferred.cpp	Allocates kWATER_1 and kWATER_2 as RGBA16 float render targets with shader resource binding; alpha channel stores premultiplied coverage for water blending passes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• community-shaders/skyrim-community-shaders#2484: Removes initialization of the same TAA water history render targets in Deferred::SetupResources() that this PR allocates.
• community-shaders/skyrim-community-shaders#2323: Consumes the allocated TAA water history render targets for coverage-based water blending logic in ISWaterBlend.hlsl.
• community-shaders/skyrim-community-shaders#1988: Related TAA water history setup and hdr water blending infrastructure in the water pipeline.

Suggested reviewers

• doodlum
• jiayev
• alandtse

Poem

🐰 A shader sprite hops through terrain deep,
sampling heights where puddles seep.
With gradients dancing and normals bent,
the wetness flows—through pixels, down, spent.
Pools form cavities, droplets gleam,
in TAA's blur of a water dream. ✨

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

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.
Title check	❓ Inconclusive	The title 'fix(water): TAA water black edge line' is somewhat vague and does not clearly convey the substantial changes made, which include adding height-aware wetness effects and TAA water history buffers.	Consider clarifying the title to better reflect the main changes, such as 'fix(water): Add height-aware wetness effects and TAA water history buffers' or similar to make the scope of changes clearer.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
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.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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): [00.12][ERROR]: Error: exception Unix_error: No such file or directory stat src/Deferred.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_CLI.re

🔧 Infer (1.2.0)

src/Deferred.cpp

Usage Error: Failed to execute compilation command:
'/opt/infer-linux-x86_64-v1.2.0/lib/infer/infer/bin/../../facebook-clang-plugins/clang/install/bin/clang++'
-c src/Deferred.cpp -o /tmp/coderabbit-infer/9aac6da5ffddefdc/file.o

Error message:
clang++: error: no such file or directory: 'src/Deferred.cpp'

*** Infer needs a working compilation command to run.

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[github-actions]

No actionable suggestions for changed features.

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

src/Deferred.cpp (1)

114-116: ⚡ Quick win

Add an issue-closing keyword in the PR description (if tracked).

Since this PR is a bug fix, please add a reference like Fixes #<id> / Closes #<id> when there is a linked issue.

As per coding guidelines, bug-fix PRs should include issue references using GitHub keywords.

🤖 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 `@src/Deferred.cpp` around lines 114 - 116, Update the PR description to
include a GitHub issue-closing keyword referencing the tracked bug (e.g., add
"Fixes #<id>" or "Closes #<id>") so the fix in Deferred.cpp (see
SetupRenderTarget calls for RE::RENDER_TARGETS::kWATER_1 and kWATER_2) will
automatically close the linked issue; if there are multiple related issues list
each with its own keyword and ensure the PR description is saved/updated before
merge.

Source: Coding guidelines

🤖 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/Wetness` Effects/Shaders/WetnessEffects/WetnessEffectsHeight.hlsli:
- Around line 57-68: GetTerrainHeightGradientNormal currently performs an unused
center height sample (hCenter) causing an extra texture fetch; remove the
hCenter declaration and its SampleTerrainDisplacementHeight call from
GetTerrainHeightGradientNormal so only the neighbor samples (used to compute hX
and hY) remain, leaving the ddx/ddy, hX/hY computation and final normalization
(mul(tbn, gradTS)) unchanged; verify no other references to hCenter in that
function.

---

Nitpick comments:
In `@src/Deferred.cpp`:
- Around line 114-116: Update the PR description to include a GitHub
issue-closing keyword referencing the tracked bug (e.g., add "Fixes #<id>" or
"Closes #<id>") so the fix in Deferred.cpp (see SetupRenderTarget calls for
RE::RENDER_TARGETS::kWATER_1 and kWATER_2) will automatically close the linked
issue; if there are multiple related issues list each with its own keyword and
ensure the PR description is saved/updated before merge.

🪄 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

Plan: Pro Plus

Run ID: 7c2f3e29-58be-45a5-aab8-d8e9db44cb16

📥 Commits

Reviewing files that changed from the base of the PR and between b74dedf and 92e1d19.

📒 Files selected for processing (2)

• features/Wetness Effects/Shaders/WetnessEffects/WetnessEffectsHeight.hlsli
• src/Deferred.cpp

[github-actions]

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