43 lines
2.3 KiB
Markdown
43 lines
2.3 KiB
Markdown
## Ray Tracing Manager: BLAS Cache and Per-Frame TLAS
|
|
|
|
Optional subsystem that enables hybrid or full ray traced shadows via Ray Query. It builds and caches BLAS per mesh and rebuilds a TLAS from the current `DrawContext` when enabled.
|
|
|
|
- Files: `src/core/vk_raytracing.h/.cpp`
|
|
|
|
### Device Feature & Extension Enablement
|
|
- Feature detection happens in `DeviceManager::init_vulkan()` and sets:
|
|
- `VK_KHR_acceleration_structure`, `VK_KHR_ray_query`, and `VK_KHR_deferred_host_operations` (if supported).
|
|
- Device features are appended via `DeviceBuilder.add_pNext(...)`.
|
|
- `DescriptorManager::gpuSceneDataLayout()` adds a TLAS binding at `(set=0, binding=1)` when AS is supported.
|
|
|
|
### BLAS Build & Cache
|
|
- `AccelStructureHandle getOrBuildBLAS(const std::shared_ptr<MeshAsset>& mesh)`:
|
|
- One GAS per `MeshAsset`, keyed by vertex buffer `VkBuffer`.
|
|
- Populated with one triangle geometry per `GeoSurface`.
|
|
- Built with `VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_KHR` and device-local storage + scratch.
|
|
- Cached in `_blasByVB` for reuse across frames.
|
|
- Called from `AssetManager::createMesh(...)` and from GLTF loader after mesh upload.
|
|
|
|
### TLAS Rebuild Per Frame
|
|
- `VkAccelerationStructureKHR buildTLASFromDrawContext(const DrawContext& dc)`:
|
|
- Iterates `dc.OpaqueSurfaces` and creates one instance per render object.
|
|
- Looks up BLAS by `RenderObject::vertexBuffer`; if missing, instance is skipped.
|
|
- Uploads instances to a CPU→GPU buffer with device address.
|
|
- Builds TLAS with `immediate_submit` and stores device address for Ray Query.
|
|
|
|
### Renderer Integration
|
|
- In `VulkanEngine::draw()` before building passes:
|
|
- If RT mode is enabled (`shadowSettings.mode != 0`) and manager exists, TLAS is rebuilt from the latest draw context.
|
|
- Lighting pass binds the TLAS at `set=0,binding=1` when available.
|
|
|
|
### Modes & UI
|
|
- Mode 0: Shadow maps only (CSM).
|
|
- Mode 1: Hybrid — selected cascades assisted by Ray Query (configurable bitmask).
|
|
- Mode 2: Ray Query only (no shadow maps).
|
|
|
|
### Notes & Caveats
|
|
- BLAS cache key is the vertex buffer handle; if you rebuild meshes in-place, BLAS must be invalidated.
|
|
- CPU→GPU memory is used for the TLAS instance buffer to simplify updates. On some platforms, you may prefer staging + device-local.
|
|
- The RT path requires Vulkan 1.2+ with Ray Query and Acceleration Structure features available.
|
|
|