revert: "perf(terrain shadows): half res and 4x faster updates"

[doodlum]

Reverts #2163

Summary by CodeRabbit

Refactor

• Streamlined terrain shadow coordinate calculations to reduce redundant dimension queries.
• Improved heightmap loading efficiency by eliminating unnecessary intermediate processing steps.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR consolidates terrain shadow rendering to use unified heightmap dimensions for both sampling and output operations. It removes separate shadow texture dimension handling, eliminates an intermediate heightmap resize step during loading, and updates dispatch coordinate calculations to reference the heightmap dimensions consistently.

Changes

Cohort / File(s)	Summary
Shader Dimension Unification features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl	Removed separate dimension queries for heightmap and shadow render target, replacing them with a single dimension derived from heightmap. Consolidated per-thread pixel coordinate calculation to use one coordinate space for both reading and writing operations, updating all corresponding indexing and function calls.
Heightmap Loading & Dispatch Logic src/Features/TerrainShadows.cpp	Eliminated intermediate DDS load and downscaling step in heightmap loading; DDS now loads directly. Changed shadow dispatch dimensions from shadow texture to heightmap dimensions. Updated pixel size constant buffer data to derive from heightmap texture rather than shadow texture.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• chore(terrain shadows): modernize #1678: Modifies the same TerrainShadows.cpp shadow/heightmap code in LoadHeightmap and UpdateShadow functions.
• build(hlsl): fix warnings #1370: Modifies the same ShadowUpdate.cs.hlsl shader file with related initialization and coordinate handling changes.
• perf(terrain shadows): half res and 4x faster updates #2163: Makes opposite changes to the same shader and heightmap/shadow dimension handling, splitting instead of consolidating coordinate spaces.

Suggested reviewers

• davo0411
• alandtse

Poem

🐰 Shadows once split in two dimensions wide,
Now unified—one heightmap as our guide!
No resizing dance, just direct and clean,
The sharpest terrain rendering ever seen! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 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 (4 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.
Title check	✅ Passed	The title accurately describes the main change: reverting a previous performance optimization for terrain shadows. It directly reflects the PR's objective.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch revert-2163-terrain-shadows-opt

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