// Copyright Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	DummyRenderResources.cpp: Implementations of frequently used render resources.
=============================================================================*/

#include "CommonRenderResources.h"
#include "Containers/DynamicRHIResourceArray.h"
#include "StereoRenderUtils.h"


TGlobalResource<FFilterVertexDeclaration, FRenderResource::EInitPhase::Pre> GFilterVertexDeclaration;
TGlobalResource<FEmptyVertexDeclaration, FRenderResource::EInitPhase::Pre> GEmptyVertexDeclaration;

TGlobalResource<FScreenRectangleVertexBuffer, FRenderResource::EInitPhase::Pre> GScreenRectangleVertexBuffer;
TGlobalResource<FScreenRectangleIndexBuffer, FRenderResource::EInitPhase::Pre> GScreenRectangleIndexBuffer;

IMPLEMENT_GLOBAL_SHADER(FScreenVertexShaderVS, "/Engine/Private/Tools/FullscreenVertexShader.usf", "MainVS", SF_Vertex);
IMPLEMENT_GLOBAL_SHADER(FInstancedScreenVertexShaderVS, "/Engine/Private/Tools/FullscreenVertexShader.usf", "MainVS", SF_Vertex);
IMPLEMENT_GLOBAL_SHADER(FCopyRectPS, "/Engine/Private/ScreenPass.usf", "CopyRectPS", SF_Pixel);

bool FInstancedScreenVertexShaderVS::ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
{
	UE::StereoRenderUtils::FStereoShaderAspects Aspects(Parameters.Platform);
	return Aspects.IsInstancedMultiViewportEnabled();
}

void FScreenRectangleVertexBuffer::InitRHI(FRHICommandListBase& RHICmdList)
{
	TResourceArray<FFilterVertex, VERTEXBUFFER_ALIGNMENT> Vertices;
	Vertices.SetNumUninitialized(6);

	Vertices[0].Position = FVector4f(1, 1, 0, 1);
	Vertices[0].UV = FVector2f(1, 1);

	Vertices[1].Position = FVector4f(0, 1, 0, 1);
	Vertices[1].UV = FVector2f(0, 1);

	Vertices[2].Position = FVector4f(1, 0, 0, 1);
	Vertices[2].UV = FVector2f(1, 0);

	Vertices[3].Position = FVector4f(0, 0, 0, 1);
	Vertices[3].UV = FVector2f(0, 0);

	//The final two vertices are used for the triangle optimization (a single triangle spans the entire viewport )
	Vertices[4].Position = FVector4f(-1, 1, 0, 1);
	Vertices[4].UV = FVector2f(-1, 1);

	Vertices[5].Position = FVector4f(1, -1, 0, 1);
	Vertices[5].UV = FVector2f(1, -1);

	// Create vertex buffer. Fill buffer with initial data upon creation
	FRHIResourceCreateInfo CreateInfo(TEXT("FScreenRectangleVertexBuffer"), &Vertices);
	VertexBufferRHI = RHICmdList.CreateVertexBuffer(Vertices.GetResourceDataSize(), BUF_Static, CreateInfo);
}

void FScreenRectangleIndexBuffer::InitRHI(FRHICommandListBase& RHICmdList)
{
	const uint16 Indices[] = 
	{
		0, 1, 2, 2, 1, 3,	// [0 .. 5]  Full screen quad with 2 triangles
		0, 4, 5,			// [6 .. 8]  Full screen triangle
		3, 2, 1				// [9 .. 11] Full screen rect defined with TL, TR, BL corners
	};

	TResourceArray<uint16, INDEXBUFFER_ALIGNMENT> IndexBuffer;
	uint32 NumIndices = UE_ARRAY_COUNT(Indices);
	IndexBuffer.AddUninitialized(NumIndices);
	FMemory::Memcpy(IndexBuffer.GetData(), Indices, NumIndices * sizeof(uint16));

	// Create index buffer. Fill buffer with initial data upon creation
	FRHIResourceCreateInfo CreateInfo(TEXT("FScreenRectangleIndexBuffer"), &IndexBuffer);
	IndexBufferRHI = RHICmdList.CreateIndexBuffer(sizeof(uint16), IndexBuffer.GetResourceDataSize(), BUF_Static, CreateInfo);
}