55 lines
2.5 KiB
Markdown
55 lines
2.5 KiB
Markdown
## Scene System: Cameras, DrawContext, and Instances
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Thin scene layer that produces `RenderObject`s for the renderer. It gathers opaque/transparent surfaces, maintains the main camera, and exposes simple runtime instance APIs.
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### Components
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- `SceneManager` (src/scene/vk_scene.h/.cpp)
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- Owns the main `Camera`, `GPUSceneData`, and `DrawContext`.
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- Loads GLTF scenes via `AssetManager`/`LoadedGLTF` and creates dynamic mesh/GLTF instances.
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- Updates per‑frame transforms, camera, and `GPUSceneData` (`view/proj/viewproj`, sun/ambient).
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- `DrawContext`
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- Two lists: `OpaqueSurfaces` and `TransparentSurfaces` of `RenderObject`.
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- Populated by scene graph traversal and dynamic instances each frame.
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- `RenderObject`
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- Geometry: `indexBuffer`, `vertexBuffer` (for RG tracking), `vertexBufferAddress` (device address used by shaders).
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- Material: `MaterialInstance* material` with bound set and pipeline.
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- Transform and bounds for optional culling.
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### Frame Flow
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1. `SceneManager::update_scene()` clears the draw lists and rebuilds them by drawing all active scene/instance nodes.
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2. Renderer consumes the lists:
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- Geometry pass sorts opaque by material and index buffer to improve locality.
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- Transparent pass sorts back‑to‑front against camera and blends to the HDR target.
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3. Uniforms: Passes allocate a small per‑frame UBO (`GPUSceneData`) and bind it via a shared layout.
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### Sorting / Culling
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- Opaque (geometry): stable sort by `material` then `indexBuffer` (see `src/render/vk_renderpass_geometry.cpp`).
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- Transparent: sort by camera‑space depth far→near (see `src/render/vk_renderpass_transparent.cpp`).
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- An example frustum test exists in `vk_renderpass_geometry.cpp` (`is_visible`) and can be enabled to cull meshes.
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### Dynamic Instances
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- Mesh instances
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- `addMeshInstance(name, mesh, transform)`, `removeMeshInstance(name)`, `clearMeshInstances()`.
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- Useful for spawning primitives or asset meshes at runtime.
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- GLTF instances
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- `addGLTFInstance(name, LoadedGLTF, transform)`, `removeGLTFInstance(name)`, `clearGLTFInstances()`.
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### GPU Scene Data
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- `GPUSceneData` carries camera matrices and lighting constants for the frame.
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- Passes map and fill it into a per‑frame UBO, bindable with `DescriptorManager::gpuSceneDataLayout()`.
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### Tips
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- Treat `DrawContext` as immutable during rendering; build it fully in `update_scene()`.
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- Keep `RenderObject` small; use device addresses for vertex data to avoid per‑draw vertex buffer binds.
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- For custom sorting/culling, modify only the scene layer; render passes stay simple.
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