ScenePrimitiveUpdates.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "SceneUpdateCommandQueue.h"
#include "PrimitiveSceneInfo.h"
#include "GPUSceneWriter.h"
 
struct FViewSceneChangeSet;
 
enum class EPrimitiveUpdateDirtyFlags : uint32 
{
    None            =   0u,
    Transform       =   1u << 0,
    InstanceData    =   1u << 1,
    CullingBounds   =   1u << 2,
    CullingLogic    =   1u << 3,
    GPUState        =   1u << 4,
    AllCulling      = CullingBounds | CullingLogic,
    All             =   GPUState |  Transform | InstanceData | CullingBounds | CullingLogic,
};
ENUM_CLASS_FLAGS(EPrimitiveUpdateDirtyFlags);
 
enum class EPrimitiveUpdateId : uint32 
{
    UpdateTransform,
    UpdateInstance,
    UpdateAttachmentRoot,
    CustomPrimitiveData,
    OcclusionBoundsSlacks,  
    InstanceCullDistance,  
    DrawDistance,
    DistanceFieldScene,
    OverridePreviousTransform,
    UpdateInstanceFromCompute,
    MAX
};
 
using FScenePrimitiveUpdates = TSceneUpdateCommandQueue<FPrimitiveSceneInfo, EPrimitiveUpdateDirtyFlags, EPrimitiveUpdateId>;
 
using FPrimitiveUpdateCommand = FScenePrimitiveUpdates::FUpdateCommand;
 
template <EPrimitiveUpdateId InId, EPrimitiveUpdateDirtyFlags InDirtyFlags>
using TPrimitiveUpdatePayloadBase = FScenePrimitiveUpdates::TPayloadBase<InId, InDirtyFlags>;
 
struct FUpdateTransformCommand : public TPrimitiveUpdatePayloadBase<EPrimitiveUpdateId::UpdateTransform, 
    EPrimitiveUpdateDirtyFlags::GPUState | EPrimitiveUpdateDirtyFlags::Transform | EPrimitiveUpdateDirtyFlags::CullingBounds>
{
    FBoxSphereBounds WorldBounds;
    FBoxSphereBounds LocalBounds; 
    FMatrix LocalToWorld; 
    FVector AttachmentRootPosition;
};
 
struct FUpdateInstanceCommand : public TPrimitiveUpdatePayloadBase<EPrimitiveUpdateId::UpdateInstance, 
    EPrimitiveUpdateDirtyFlags::GPUState | EPrimitiveUpdateDirtyFlags::Transform | EPrimitiveUpdateDirtyFlags::CullingBounds | EPrimitiveUpdateDirtyFlags::InstanceData>
{
    FPrimitiveSceneProxy* PrimitiveSceneProxy{ nullptr };
    FBoxSphereBounds WorldBounds;
    FBoxSphereBounds LocalBounds;
};
 
struct FUpdateInstanceFromComputeCommand : public TPrimitiveUpdatePayloadBase<EPrimitiveUpdateId::UpdateInstanceFromCompute, EPrimitiveUpdateDirtyFlags::CullingBounds | EPrimitiveUpdateDirtyFlags::InstanceData>
{
    FPrimitiveSceneProxy* PrimitiveSceneProxy{ nullptr };
    FGPUSceneWriteDelegate GPUSceneWriter;
};
 
template <typename InPayloadDataType, EPrimitiveUpdateId InId, EPrimitiveUpdateDirtyFlags InPrimitiveDirtyFlags>
struct TSingleValuePrimitiveUpdatePayload : public TPrimitiveUpdatePayloadBase<InId, InPrimitiveDirtyFlags>
{
    TSingleValuePrimitiveUpdatePayload(const InPayloadDataType &InValue) : Value(InValue) {}
    InPayloadDataType Value;
};
 
using FUpdateAttachmentRootData = TSingleValuePrimitiveUpdatePayload<FPrimitiveComponentId, EPrimitiveUpdateId::UpdateAttachmentRoot,
    EPrimitiveUpdateDirtyFlags::None>; // No GPU side effect (?).
using FUpdateCustomPrimitiveData = TSingleValuePrimitiveUpdatePayload<FCustomPrimitiveData, EPrimitiveUpdateId::CustomPrimitiveData,
    EPrimitiveUpdateDirtyFlags::GPUState>; // Needs upload
using FUpdateOcclusionBoundsSlacksData = TSingleValuePrimitiveUpdatePayload<float, EPrimitiveUpdateId::OcclusionBoundsSlacks,  
    EPrimitiveUpdateDirtyFlags::None>; // Only affects primitive occlusion.
using FUpdateInstanceCullDistanceData = TSingleValuePrimitiveUpdatePayload<FVector2f, EPrimitiveUpdateId::InstanceCullDistance,  
    EPrimitiveUpdateDirtyFlags::GPUState | EPrimitiveUpdateDirtyFlags::CullingLogic>; // Affects GPU culling?
using FUpdateDrawDistanceData = TSingleValuePrimitiveUpdatePayload<FVector3f, EPrimitiveUpdateId::DrawDistance,  
    EPrimitiveUpdateDirtyFlags::CullingLogic>; // Only affects CPU culling.
using FUpdateDistanceFieldSceneData = TPrimitiveUpdatePayloadBase<EPrimitiveUpdateId::DistanceFieldScene,  
    EPrimitiveUpdateDirtyFlags::None>; // Only affects DF scene rep - candidate for using abstract type.
using FUpdateOverridePreviousTransformData = TSingleValuePrimitiveUpdatePayload<FMatrix, EPrimitiveUpdateId::OverridePreviousTransform,  
    EPrimitiveUpdateDirtyFlags::GPUState>;// Overrides the previous transform, which needs to be propagated to the GPU, but otherwise does not change anything on its own.
 
class FScenePreUpdateChangeSet
{
public:
    TConstArrayView<FPersistentPrimitiveIndex> RemovedPrimitiveIds;
    TConstArrayView<FPrimitiveSceneInfo*> RemovedPrimitiveSceneInfos;
    const FScenePrimitiveUpdates &PrimitiveUpdates;
    const FViewSceneChangeSet* ViewUpdateChangeSet = nullptr;
};
 
class FScenePostUpdateChangeSet
{
public:
    TConstArrayView<FPersistentPrimitiveIndex> AddedPrimitiveIds;
    TConstArrayView<FPrimitiveSceneInfo*> AddedPrimitiveSceneInfos;
    const FScenePrimitiveUpdates &PrimitiveUpdates;
    const FViewSceneChangeSet* ViewUpdateChangeSet = nullptr;
};