Dev → Main: Modern Lighting Overhaul, HDR Pipeline, and Major Refactors

[MichaelFisher1997]

Summary

This PR merges all development work from the dev branch into main, bringing 47 commits of significant improvements to ZigCraft's rendering system, lighting, and overall architecture.

Major Features

Modern Lighting Overhaul

• LPV (Light Propagation Volume) compute GI with occlusion support
• PCSS (Percentage-Closer Soft Shadows) for soft shadows
• Spherical Harmonics L1 lighting calculations
• LUT-based color grading for enhanced visuals
• 3D dummy texture fix for proper volume rendering

Industry-Grade Shadow System

• Reverse-Z depth buffer for better precision
• 16-tap PCF (Percentage-Closer Filtering)
• Configurable shadow distance
• CSM (Cascaded Shadow Maps) with improved snapping
• Fixed intermittent massive shadow artifacts below player

HDR Pipeline & Post-Processing

• HDR rendering pipeline
• FXAA anti-aliasing
• Bloom effects
• SSAO (Screen Space Ambient Occlusion) with blur
• Smooth LOD transitions with AO smoothing
• Grid-free texture rendering

Major Refactors

RHI (Render Hardware Interface)

• Split monolithic Vulkan backend into focused modules
• Added PipelineManager and RenderPassManager
• Decoupled LOD logic from GPU operations

World Generation

• Split biome.zig into focused sub-modules
• Split overworld generator into focused subsystems
• Extracted chunk_mesh.zig meshing stages into independent modules

Input System

• Refactored to SOLID interfaces
• Human-readable settings with debouncing
• Keymap improvements with bug fixes

Bug Fixes

• Shadow artifacts and cloud shadow blob artifacts
• SSAO artifacts in LOD
• PBR lighting energy conservation
• Shadow regression and CSM bounds
• Various code review feedback items addressed

Testing

All pre-push checks passed including:

• Code formatting validation
• Full test suite
• Shader validation (43 Vulkan shaders)

Breaking Changes

None - all changes are additive or internal refactors.