refactor(TAA): readable variable names + named constants

[alandtse]

Behavior-preserving readability pass on the ISTemporalAA.hlsl decompile transcription. Supersedes #85 (its constants + alpha-loop commits are included here) — folded into one cohesive PR.

What changed (all bytecode-identical)

1. Named constants for repeated magic literals: kMaxLumaCap, kMinLumaCap, kLumaEpsilon, kSimilarityScale.
2. Alpha-coverage loop replacing eight near-identical AlphaCoverageMask(...) ? x : 0 lines.
3. Real variable names for clean register lifetimes: centerLuma, centerColor, neighborColor, motionLength, motionConfidence, motionNormScale, feedbackWeight, depthMaskPass, allTransparent, centerCoverage, uvMinCoverage, uvMinBelowHist, outputLuma, resolved, flickerScore, historyBlend, clampToNeighborhood, reject.

Proven safe

Every step gated by tools/verify-shader-refactor.ps1 (#86): compiled DXBC is byte-identical (SHA-256) to the pre-refactor revision across all four permutations (flat / VR / HDR / VR+HDR). No math, swizzle, control-flow, or #ifdef changes. Also deployed + spot-checked in-game.

Out of scope (Standard B, separate follow-up)

The dense bracket-selection cascade and flicker bubble-passes stay as register packs — restructuring those into helpers/loops diverges bytecode and needs runtime A/B validation; tracked separately, ideally upstreamed.

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⚙️ Run configuration

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📥 Commits

Reviewing files that changed from the base of the PR and between a47f46b and a02a2f9.

📒 Files selected for processing (1)

• package/Shaders/ISTemporalAA.hlsl

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/taa-readable-vars

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[github-actions]

No actionable suggestions for changed features.

[Copilot]

Pull request overview

Readability-focused refactor of the ISTemporalAA.hlsl decompile transcription, aiming to keep the shader behavior/compiled output unchanged while making the code easier to follow and maintain.

Changes:

• Introduces named constants for repeated “magic” literals used in luma clamping/thresholding and similarity scaling.
• Replaces repeated alpha-coverage gating statements with a compact unrolled loop.
• Renames key intermediate values (e.g., center/neighbor luma/color, motion metrics, flicker/history blend factors) to better communicate intent and register lifetimes.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

[alandtse]

Consolidated into #98, which now targets dev directly with the full ISTemporalAA refactor (readable vars + core restructure + register-pack destructure).