MetalRayTracing.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
/*==============================================================================
    MetalRayTracing.h: MetalRT Implementation
==============================================================================*/
 
#pragma once
 
#include "MetalRHIPrivate.h"
#include "MetalResources.h"
#include "RayTracingBuiltInResources.h"
 
#if METAL_RHI_RAYTRACING
 
struct FMetalHitGroupSystemParameters
{   
    uint32 BindlessHitGroupSystemIndexBuffer;
    uint32 BindlessHitGroupSystemVertexBuffer;
    
    FHitGroupSystemRootConstants RootConstants;
};
 
class FMetalRayTracingGeometry : public FRHIRayTracingGeometry
{
public:
    FMetalRayTracingGeometry(FMetalDevice& InDevice, FRHICommandListBase& RHICmdList, const FRayTracingGeometryInitializer& InInitializer);
    ~FMetalRayTracingGeometry();
 
    void ReleaseUnderlyingResource();
    void ReleaseDescriptors();
    
    virtual FRayTracingAccelerationStructureAddress GetAccelerationStructureAddress(uint64 GPUIndex) const final override;
    void Swap(FMetalRayTracingGeometry& Other);
    void RebuildDescriptors();
 
    void RemoveCompactionRequest();
 
    using FRHIRayTracingGeometry::Initializer;
    using FRHIRayTracingGeometry::SizeInfo;
 
    MTL::PrimitiveAccelerationStructureDescriptor* AccelerationStructureDescriptor = nullptr;
 
    bool bHasPendingCompactionRequests;
    uint32 CompactionSizeIndex;
 
    static constexpr uint32 IndicesPerPrimitive = 3; // Triangle geometry only
 
    inline FMetalAccelerationStructure* GetAccelerationStructure() const
    {
        return AccelerationStructure;
    }
    
    void SetAccelerationStructure(FMetalAccelerationStructure* InBuffer);
    void SetupHitGroupSystemParameters();
    void ReleaseBindlessHandles();
    
    TArray<FMetalHitGroupSystemParameters> HitGroupSystemParameters;
    
private:
    FMetalDevice& Device;
    
    TArray<MTL::AccelerationStructureTriangleGeometryDescriptor*> GeomArray;
 
    uint32 AccelerationStructureIndex;
    FMetalAccelerationStructure* AccelerationStructure = nullptr;
    
    TArray<FRHIDescriptorHandle> HitGroupSystemVertexViews;
    FRHIDescriptorHandle HitGroupSystemIndexView;
    
    NS::Array* GeometryDescriptors =  nullptr;
};
 
class FMetalRayTracingScene : public FRHIRayTracingScene
{
public:
    FMetalRayTracingScene(FMetalDevice& InDevice, FRayTracingSceneInitializer InInitializer);
    virtual ~FMetalRayTracingScene();
 
    void BindBuffer(FRHIBuffer* InBuffer, uint32 InBufferOffset);
    void BuildAccelerationStructure(
        FMetalRHICommandContext& CommandContext,
        FMetalRHIBuffer* ScratchBuffer, uint32 ScratchOffset,
        FMetalRHIBuffer* InstanceBuffer, uint32 InstanceOffset,
        FMetalRHIBuffer* HitGroupContributionsBuffer, uint32 HitGroupContributionsBufferOffset, 
        uint32 NumInstances);
 
    inline const FRayTracingSceneInitializer& GetInitializer() const override final { return Initializer; }
 
    // Unique list of geometries referenced by all instances in this scene.
    // Any referenced geometry is kept alive while the scene is alive.
    TArray<TRefCountPtr<FRHIRayTracingGeometry>> ReferencedGeometries;
    
    FMetalAccelerationStructure* GetAccelerationStructure()
    {
        check(AccelerationStructureBuffer && AccelerationStructureBuffer->AccelerationStructure);
        return AccelerationStructureBuffer->AccelerationStructure;
    }
    
private:
    friend class FMetalRHICommandContext;
 
private:
    FMetalDevice& Device;
    
    const FRayTracingSceneInitializer Initializer;
 
    FMetalRHIBuffer* AccelerationStructureBuffer; 
};
#endif // METAL_RHI_RAYTRACING