Phase 4 / Task 2: Adapt current culling implementation behind interface

[MichaelFisher1997]

Goal

Make the current culling system implement the new abstraction without changing behavior.

Scope

• culling implementation files

Work

• Adapt the existing culling system to the new interface
• Preserve CPU/GPU fallback behavior
• Keep frame-indexed read/write semantics stable

Acceptance criteria

• Existing culling behavior remains unchanged
• The adapter compiles with the new interface

Parallel-safe

Yes

[github-actions]

Classification: Feature Request / Refactoring

This issue describes a refactoring task to wrap the existing CullingSystem (src/engine/graphics/vulkan/culling_system.zig) behind a vtable-based interface pattern, consistent with the existing RHI abstraction architecture in src/engine/graphics/rhi.zig.

Analysis:

The codebase already follows this interface pattern for multiple subsystems:

• IShadowContext (rhi.zig:373)
• IWaterContext (rhi.zig:428)
• IUIContext (rhi.zig:477)
• ICullingContext would follow the same structure

The CullingSystem in culling_system.zig exposes these methods that would need to be behind an interface:

• updateAABBData(frame_index, chunks) - line 121
• dispatch(view_proj, chunk_count, screen_width, screen_height, previous_frame_valid) - line 132
• readVisibleCount(frame_index) - line 220
• readVisibleIndices(frame_index, count, out) - line 227

Scope Assessment: The task is appropriately scoped. It focuses on a single subsystem (culling), preserves existing behavior, and has clear acceptance criteria. No need to split into sub-issues.

Validation: No duplicates or related PRs found. The pattern is consistent with the established architecture.

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