ADD: Ray tracing shadow with Clipmap shadow blending

src/core/vk_raytracing.h

@@ -0,0 +1,52 @@
+ #pragma once
+ #include <core/vk_types.h>
+ #include <unordered_map>
+ #include <vector>
+ #include <memory>
+ 
+ class DeviceManager;
+ class ResourceManager;
+ struct DrawContext;
+ struct MeshAsset;
+ 
+ struct AccelStructureHandle {
+     VkAccelerationStructureKHR handle{VK_NULL_HANDLE};
+     AllocatedBuffer storage{}; // buffer that backs the AS
+     VkDeviceAddress deviceAddress{0};
+ };
+ 
+ class RayTracingManager {
+ public:
+     void init(DeviceManager* dev, ResourceManager* res);
+     void cleanup();
+ 
+     // Build (or get) BLAS for a mesh. Safe to call multiple times.
+     AccelStructureHandle getOrBuildBLAS(const std::shared_ptr<MeshAsset>& mesh);
+ 
+     // Rebuild TLAS from current draw context; returns TLAS handle (or null if unavailable)
+     VkAccelerationStructureKHR buildTLASFromDrawContext(const DrawContext& dc);
+     VkAccelerationStructureKHR tlas() const { return _tlas.handle; }
+     VkDeviceAddress tlasAddress() const { return _tlas.deviceAddress; }
+ 
+ private:
+     // function pointers (resolved on init)
+     PFN_vkCreateAccelerationStructureKHR            _vkCreateAccelerationStructureKHR{};
+     PFN_vkDestroyAccelerationStructureKHR           _vkDestroyAccelerationStructureKHR{};
+     PFN_vkGetAccelerationStructureBuildSizesKHR     _vkGetAccelerationStructureBuildSizesKHR{};
+     PFN_vkCmdBuildAccelerationStructuresKHR         _vkCmdBuildAccelerationStructuresKHR{};
+     PFN_vkGetAccelerationStructureDeviceAddressKHR  _vkGetAccelerationStructureDeviceAddressKHR{};
+ 
+     DeviceManager* _device{nullptr};
+     ResourceManager* _resources{nullptr};
+ 
+     // BLAS cache by vertex buffer handle
+     std::unordered_map<VkBuffer, AccelStructureHandle> _blasByVB;
+ 
+     // TLAS + scratch / instance buffer (rebuilt per frame)
+     AccelStructureHandle _tlas{};
+     AllocatedBuffer _tlasInstanceBuffer{};
+     size_t _tlasInstanceCapacity{0};
+ 
+     void ensure_tlas_storage(VkDeviceSize requiredASSize, VkDeviceSize requiredScratch);
+ };
+