UnrealEngineUWP/Engine/Shaders/Private/LightmapData.ush

// Copyright 1998-2019 Epic Games, Inc. All Rights Reserved.

/**
 * LightmapData.ush
 */

#pragma once

#if VF_USE_PRIMITIVE_SCENE_DATA

// Must match FPrecomputedLightingUniformParameters in C++
struct FLightmapSceneData
{
	float4 StaticShadowMapMasks;
	float4 InvUniformPenumbraSizes;
	float4 LightMapCoordinateScaleBias;
	float4 ShadowMapCoordinateScaleBias;
	float4 LightMapScale[2];
	float4 LightMapAdd[2];
};

// Stride of a single lightmap data entry in float4's, must match C++
#define LIGHTMAP_SCENE_DATA_STRIDE 8

// Fetch from scene lightmap data buffer
FLightmapSceneData GetLightmapData(uint LightmapDataIndex) 
{
	// Note: layout must match FLightmapSceneShaderData in C++
	// Relying on optimizer to remove unused loads

	FLightmapSceneData LightmapData;
	uint LightmapDataBaseOffset = LightmapDataIndex * LIGHTMAP_SCENE_DATA_STRIDE;
	LightmapData.StaticShadowMapMasks = View.LightmapSceneData[LightmapDataBaseOffset + 0];
	LightmapData.InvUniformPenumbraSizes = View.LightmapSceneData[LightmapDataBaseOffset + 1];
	LightmapData.LightMapCoordinateScaleBias = View.LightmapSceneData[LightmapDataBaseOffset + 2];
	LightmapData.ShadowMapCoordinateScaleBias = View.LightmapSceneData[LightmapDataBaseOffset + 3];
	LightmapData.LightMapScale[0] = View.LightmapSceneData[LightmapDataBaseOffset + 4];
	LightmapData.LightMapScale[1] = View.LightmapSceneData[LightmapDataBaseOffset + 5];
	LightmapData.LightMapAdd[0] = View.LightmapSceneData[LightmapDataBaseOffset + 6];
	LightmapData.LightMapAdd[1] = View.LightmapSceneData[LightmapDataBaseOffset + 7];

	return LightmapData;
}

#else 

// Route to uniform buffer
#define GetLightmapData(x) PrecomputedLightingBuffer

#endif