fix: water reflection flicker

[Dlizzio]

Summary by CodeRabbit

• Bug Fixes
  • Improved water blending calculations for more accurate visual representation in water shader rendering.

[coderabbitai]

📝 Walkthrough

Walkthrough

ISWaterBlend.hlsl refactors water history blending by replacing a hard historyMask threshold with computed historyCoverage. A new WaterBlend namespace defines threshold constants and helper functions to clamp the history mask into a normalized coverage value, which then gates and scales the blend between source and water history colors.

Changes

Water Blend History Coverage Refactor

Layer / File(s)	Summary
Water coverage computation helpers package/Shaders/ISWaterBlend.hlsl	Math.hlsli include added. WaterBlend namespace introduces WaterMaskThreshold, FullHistoryCoverageThreshold constants and SaturateRange(), GetHistoryCoverage() helpers to compute clamped history coverage from the sampled mask.
Apply coverage-based blending package/Shaders/ISWaterBlend.hlsl	Blend condition now gates on historyCoverage > 0.0 and scales historyFactor by computed historyCoverage, replacing prior raw-mask threshold comparison.

Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly Related PRs

• community-shaders/skyrim-community-shaders#1988: Modifies ISWaterBlend.hlsl water-history gating logic, with overlapping changes to the same shader blending path.
• community-shaders/skyrim-community-shaders#2011: Updates ISWaterBlend.hlsl to change how historyMask controls sourceColor/waterHistory blending.

Suggested Reviewers

• jiayev
• alandtse
• SkrubbySkrubInAShrub

Poem

🐰 A shader's mask grows soft and kind,
No longer hard, but gently defined,
Water blends with measured care,
Coverage flows through thinning air. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing water reflection flicker by refactoring the water blending history logic.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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)

• Create PR with unit tests

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[github-actions]

No actionable suggestions for changed features.

[coderabbitai]

🧹 Nitpick comments (1)

package/Shaders/ISWaterBlend.hlsl (1)

48-93: Add an issue-closing reference in the PR description.

Since this is a bug-fix PR, consider adding Fixes #<id> / Closes #<id> for traceability and auto-close behavior.

As per coding guidelines, "When reviewing PRs... suggest adding appropriate GitHub keywords: 'Fixes #123' or 'Closes #123' for bug fixes".

🤖 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 `@package/Shaders/ISWaterBlend.hlsl` around lines 48 - 93, The PR is a bug-fix
for ISWaterBlend.hlsl (function main) but the PR description lacks an
issue-closing keyword; update the PR description to include a GitHub keyword
like "Fixes #<issue-number>" or "Closes #<issue-number>" referencing the bug
tracked for this change so the issue will auto-close when merged (e.g., add
"Fixes `#123`" to the PR body).

🤖 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.

Nitpick comments:
In `@package/Shaders/ISWaterBlend.hlsl`:
- Around line 48-93: The PR is a bug-fix for ISWaterBlend.hlsl (function main)
but the PR description lacks an issue-closing keyword; update the PR description
to include a GitHub keyword like "Fixes #<issue-number>" or "Closes
#<issue-number>" referencing the bug tracked for this change so the issue will
auto-close when merged (e.g., add "Fixes `#123`" to the PR body).

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: dde43e50-2958-42ab-bab7-efefa4d9553a

📥 Commits

Reviewing files that changed from the base of the PR and between cefdcde and eefb4d4.

📒 Files selected for processing (1)

• package/Shaders/ISWaterBlend.hlsl