Phase 2 / Task 1: Move AtmosphereSystem ownership into render graph

[MichaelFisher1997]

Goal

Move atmosphere ownership out of RenderSystem and into the render-graph setup path.

Scope

• src/engine/graphics/render_system.zig
• src/engine/graphics/render_graph.zig

Work

• Shift atmosphere setup/ownership to the graph path where practical
• Pass only the interfaces the passes need
• Remove RenderSystem-only wiring for atmosphere

Acceptance criteria

• RenderSystem no longer owns atmosphere as a core concern
• Sky rendering still works

Parallel-safe

Yes

[github-actions]

Analysis Comment

Classification: Refactoring task (Feature Request)

Current Ownership Chain:

RenderSystem (owns) → AtmosphereSystem
                           ↓
SceneContext (receives via getAtmosphereSystem())
                           ↓
SkyPass / CloudPass (use for rendering)

Key Findings:

1. AtmosphereSystem (src/engine/graphics/atmosphere_system.zig:10-117) is well-decoupled — it holds only GPU buffer resources (cloud mesh VBO/EB0) and render methods. The atmospheric state (colors, sun direction, fog) flows in via SkyParams/CloudParams each frame, not from owned fields.

2. RenderSystem (src/engine/graphics/render_system.zig:31) owns the atmosphere_system pointer, initializes it at line 144, and exposes it via getAtmosphereSystem() at line 305.

3. RenderGraph.SceneContext (src/engine/graphics/render_graph.zig:65) receives *AtmosphereSystem and passes it to SkyPass (line 321) and CloudPass (line 373).

Suggested Implementation Path:

1. Move AtmosphereSystem allocation/initialization from RenderSystem.init to the render graph construction path (likely where SceneContext is built, e.g., world.zig:295-331).

2. Pass atmosphere_system directly into SceneContext during construction instead of retrieving it from RenderSystem.

3. Remove atmosphere_system field and getAtmosphereSystem() from RenderSystem.

4. Remove atmosphere_system from SceneContext if the passes can receive it as a temporary or via a narrower interface.

Scope Assessment: Well-scoped. Changes are confined to two files as specified. No cross-subsystem impacts. Parallel-safe as noted.

Duplicates/Related Work: None found. This is a clean ownership refactor.

No blockers. Clear, implementable task.

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