// Copyright UShaderLab. All Rights Reserved.
//
// UE_ scene-texture reads — forward to the engine's SceneTextureLookup (MaterialTemplate.ush). Because
// these take a dynamic UV they are emitted as HLSL helpers (like Noise), NOT wired intrinsics. The graph
// builder places a hidden UMaterialExpressionSceneTexture node (wired to the ParameterAnchor) whenever a
// body uses one of these, so the engine sets bNeedsSceneTextures and binds the scene-texture SRVs.
//
// Enum scheme B (see Noise.ush): under SHADERLAB_IDE the id is a real HLSL `enum` for completion/semantics;
// at real compile it degrades to `int` + `#define`s aliasing the engine's PPI_* ids (defined in the material
// environment), so no magic numbers are hard-coded here.
//
// Domain rules (enforced by the builder, mirroring the engine): SceneDepth/CustomDepth/CustomStencil work in
// a translucent Surface, Decal, or PostProcess material; the full GBuffer / PostProcessInput ids require the
// PostProcess (or Decal) domain. (Scene-color-behind-translucency uses a different engine path and is not
// exposed here yet — read it as PostProcessInput0 in a PostProcess material instead.)

#pragma once

#ifdef SHADERLAB_IDE
	enum ESLSceneTexture
	{
		SL_ST_SceneColor,
		SL_ST_SceneDepth,
		SL_ST_CustomDepth,
		SL_ST_CustomStencil,
		SL_ST_WorldNormal,
		SL_ST_PostProcessInput0,
		SL_ST_PostProcessInput1,
		SL_ST_PostProcessInput2,
		SL_ST_PostProcessInput3,
		SL_ST_PostProcessInput4,
	};
	float4 SceneTextureLookup(float2 UV, int SceneTextureIndex, bool bFiltered) { return (float4)0; }
#else
	#define ESLSceneTexture int
	#define SL_ST_SceneColor         PPI_SceneColor
	#define SL_ST_SceneDepth         PPI_SceneDepth
	#define SL_ST_CustomDepth        PPI_CustomDepth
	#define SL_ST_CustomStencil      PPI_CustomStencil
	#define SL_ST_WorldNormal        PPI_WorldNormal
	#define SL_ST_PostProcessInput0  PPI_PostProcessInput0
	#define SL_ST_PostProcessInput1  PPI_PostProcessInput1
	#define SL_ST_PostProcessInput2  PPI_PostProcessInput2
	#define SL_ST_PostProcessInput3  PPI_PostProcessInput3
	#define SL_ST_PostProcessInput4  PPI_PostProcessInput4
#endif

// Full-control lookup: read any scene-texture id at UV (id is an ESLSceneTexture token).
float4 UE_SceneTexture(ESLSceneTexture Id, float2 UV)
{
	return SceneTextureLookup(UV, Id, false);
}

// Convenience wrappers for the common reads.
float  UE_SceneDepth(float2 UV)    { return SceneTextureLookup(UV, SL_ST_SceneDepth, false).r; }
float  UE_CustomDepth(float2 UV)   { return SceneTextureLookup(UV, SL_ST_CustomDepth, false).r; }
float  UE_CustomStencil(float2 UV) { return SceneTextureLookup(UV, SL_ST_CustomStencil, false).r; }