// Copyright 2019-Present LexLiu. All Rights Reserved.
#include "/Engine/Private/Common.ush"

struct FLGUIVertexFactoryInterpolantsVSToPS
{
    //TangentToWorld0 && TangentToWorld2
	TANGENTTOWORLD_INTERPOLATOR_BLOCK
    //float4 TangentToWorld0 : TEXCOORD3;
    //float4 TangentToWorld2 : TEXCOORD4;
	
    float4 Color : COLOR0;

#if NUM_TEX_COORD_INTERPOLATORS
	float4	TexCoords[(NUM_TEX_COORD_INTERPOLATORS + 1) / 2]	: TEXCOORD0;
#endif
};

#if NUM_TEX_COORD_INTERPOLATORS
float2 GetUV(FLGUIVertexFactoryInterpolantsVSToPS Interpolants, int UVIndex)
{
	float4 UVVector = Interpolants.TexCoords[UVIndex / 2];
	return UVIndex % 2 ? UVVector.zw : UVVector.xy;
}

void SetUV(inout FLGUIVertexFactoryInterpolantsVSToPS Interpolants, int UVIndex, float2 InValue)
{
	FLATTEN
	if (UVIndex % 2)
	{
		Interpolants.TexCoords[UVIndex / 2].zw = InValue;
	}
	else
	{
		Interpolants.TexCoords[UVIndex / 2].xy = InValue;
	}
}
#endif

float4 GetColor(FLGUIVertexFactoryInterpolantsVSToPS Interpolants)
{
	return Interpolants.Color;
}

void SetColor(inout FLGUIVertexFactoryInterpolantsVSToPS Interpolants, float4 InValue)
{
	Interpolants.Color = InValue;
}

float4 GetTangentToWorld2(FLGUIVertexFactoryInterpolantsVSToPS Interpolants)
{
    return Interpolants.TangentToWorld2;
}

float4 GetTangentToWorld0(FLGUIVertexFactoryInterpolantsVSToPS Interpolants)
{
    return Interpolants.TangentToWorld0;
}

void SetTangents(inout FLGUIVertexFactoryInterpolantsVSToPS Interpolants, float3 InTangentToWorld0, float3 InTangentToWorld2, float InTangentToWorldSign)
{
    Interpolants.TangentToWorld0 = float4(InTangentToWorld0, 0);
    Interpolants.TangentToWorld2 = float4(InTangentToWorld2, InTangentToWorldSign);
}

half3x3 CalcTangentToLocal(HALF3_TYPE TangentInputX, HALF4_TYPE TangentInputZ, out float TangentSign)
{
    half3x3 Result;

    HALF3_TYPE TangentX = TangentBias(TangentInputX);
    HALF4_TYPE TangentZ = TangentBias(TangentInputZ);

    TangentSign = TangentZ.w;

	// derive the binormal by getting the cross product of the normal and tangent
    HALF3_TYPE TangentY = cross(TangentZ.xyz, TangentX) * TangentZ.w;
	
	// Recalculate TangentX off of the other two vectors
	// This corrects quantization error since TangentX was passed in as a quantized vertex input
	// The error shows up most in specular off of a mesh with a smoothed UV seam (normal is smooth, but tangents vary across the seam)
    Result[0] = cross(TangentY, TangentZ.xyz) * TangentZ.w;
    Result[1] = TangentY;
    Result[2] = TangentZ.xyz;

    return Result;
}

half3x3 CalcTangentToWorldNoScale(half3x3 TangentToLocal, half3x3 LocalToWorld, HALF3_TYPE InvScale)
{
    LocalToWorld[0] *= InvScale.x;
    LocalToWorld[1] *= InvScale.y;
    LocalToWorld[2] *= InvScale.z;
    return mul(TangentToLocal, LocalToWorld);
}

half3x3 CalcTangentToWorld(half3x3 TangentToLocal, half3x3 LocalToWorld, HALF3_TYPE InvScale)
{
    half3x3 TangentToWorld = CalcTangentToWorldNoScale(TangentToLocal, LocalToWorld, InvScale);
    return TangentToWorld;
}