UniformBuffer.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
/*=============================================================================
    UniformBuffer.h: Uniform buffer declarations.
=============================================================================*/
 
#pragma once
 
#include "ShaderParameterMacros.h"
#include "RenderingThread.h"
#include "RenderResource.h"
#include "Templates/IsArrayOrRefOfType.h"
 
class FShaderUniformBufferParameter;
template<typename TBufferStruct> class TShaderUniformBufferParameter;
 
template<typename TBufferStruct>
TUniformBufferRef<TBufferStruct> CreateUniformBufferImmediate(const TBufferStruct& Value, EUniformBufferUsage Usage, EUniformBufferValidation Validation = EUniformBufferValidation::ValidateResources)
{
    return TUniformBufferRef<TBufferStruct>::CreateUniformBufferImmediate(Value, Usage, Validation);
}
 
 
template<typename TBufferStruct>
class TUniformBuffer : public FRenderResource
{
    static_assert(!TIsUECoreVariant<TBufferStruct, double>::Value, "UniformBufferRHIRef cannot be double core variants! Switch to float variant.");
 
public:
 
    TUniformBuffer()
        : BufferUsage(UniformBuffer_MultiFrame)
        , Contents(nullptr)
    {
    }
 
    ~TUniformBuffer()
    {
        if (Contents)
        {
            FMemory::Free(Contents);
        }
    }
 
    void SetContents(FRHICommandListBase& RHICmdList, const TBufferStruct& NewContents)
    {
        SetContentsNoUpdate(NewContents);
        UpdateRHI(RHICmdList);
    }
 
    UE_DEPRECATED(5.4, "SetContents requires a command list.")
    void SetContents(const TBufferStruct& NewContents)
    {
        SetContents(FRenderResource::GetImmediateCommandList(), NewContents);
    }
 
    void SetContentsToZero(FRHICommandListBase& RHICmdList)
    {
        if (!Contents)
        {
            Contents = (uint8*)FMemory::Malloc(sizeof(TBufferStruct), SHADER_PARAMETER_STRUCT_ALIGNMENT);
        }
        FMemory::Memzero(Contents, sizeof(TBufferStruct));
        UpdateRHI(RHICmdList);
    }
 
    UE_DEPRECATED(5.4, "SetContentsToZero requires a command list.")
    void SetContentsToZero()
    {
        SetContentsToZero(FRenderResource::GetImmediateCommandList());
    }
 
    const uint8* GetContents() const 
    {
        return Contents;
    }
 
    // FRenderResource interface.
    virtual void InitRHI(FRHICommandListBase& RHICmdList) override
    {
        UniformBufferRHI.SafeRelease();
        if (Contents)
        {
            UniformBufferRHI = CreateUniformBufferImmediate<TBufferStruct>(*((const TBufferStruct*)Contents), BufferUsage);
        }
    }
    virtual void ReleaseRHI() override
    {
        UniformBufferRHI.SafeRelease();
    }
 
    // Accessors.
    FRHIUniformBuffer* GetUniformBufferRHI() const
    { 
        checkSlow(IsInParallelRenderingThread() || IsInRenderingThread());
        checkf(UniformBufferRHI.GetReference(), TEXT("Attempted to access UniformBufferRHI on a TUniformBuffer that was never filled in with anything")); 
        check(UniformBufferRHI.GetReference()); // you are trying to use a UB that was never filled with anything
        return UniformBufferRHI; 
    }
 
    const TUniformBufferRef<TBufferStruct>& GetUniformBufferRef() const
    {
        check(UniformBufferRHI.GetReference()); // you are trying to use a UB that was never filled with anything
        return UniformBufferRHI;
    }
 
    EUniformBufferUsage BufferUsage;
 
protected:
 
    void SetContentsNoUpdate(const TBufferStruct& NewContents)
    {
        if (!Contents)
        {
            Contents = (uint8*)FMemory::Malloc(sizeof(TBufferStruct), SHADER_PARAMETER_STRUCT_ALIGNMENT);
        }
        FMemory::Memcpy(Contents,&NewContents,sizeof(TBufferStruct));
    }
 
private:
 
    TUniformBufferRef<TBufferStruct> UniformBufferRHI;
    uint8* Contents;
};
 
 
template<typename TBufferStruct>
void BeginSetUniformBufferContents(
    TUniformBuffer<TBufferStruct>& UniformBuffer,
    const TBufferStruct& Struct
    )
{
    TUniformBuffer<TBufferStruct>* UniformBufferPtr = &UniformBuffer;
    ENQUEUE_RENDER_COMMAND(SetUniformBufferContents)(
        [UniformBufferPtr, Struct](FRHICommandListImmediate& RHICmdList)
        {
            UniformBufferPtr->SetContents(RHICmdList, Struct);
        });
}