//========== Copyright (c) Valve Corporation, All rights reserved. ==========//

// DYNAMIC: "COMPRESSED_VERTS"			"0..1"
// DYNAMIC: "SKINNING"					"0..1"

// Includes
#include "common_vs_fxc.h"

// Globals
const float  g_flUVScale		: register( SHADER_SPECIFIC_CONST_0 );
const float3 g_vUVProjOffset	: register( SHADER_SPECIFIC_CONST_1 );
const float3 g_vBBMin			: register( SHADER_SPECIFIC_CONST_2 );
const float3 g_vBBMax			: register( SHADER_SPECIFIC_CONST_3 );

// Structs
struct VS_INPUT
{
	float4 vPos					: POSITION;		// Position
	float4 vNormal				: NORMAL;		// Normal
	float4 vBoneWeights			: BLENDWEIGHT;	// Skin weights
	float4 vBoneIndices			: BLENDINDICES;	// Skin indices
	float4 vClosestSurfaceDir	: TEXCOORD0;	
	float4 vTangent				: TANGENT;
};

struct VS_OUTPUT
{
    float4 vProjPosition		: POSITION;		// Projection-space position
	float4 vWorldNormal			: TEXCOORD0;	// w is proj. z coord (for depth stuff)
	float4 vClosestSurfaceDir	: TEXCOORD1;
	float4 vWorldPos			: TEXCOORD2;	// w is proj. w coord
	float4 vUV0					: TEXCOORD3;
	float4 vUV1					: TEXCOORD4;
	float4 vLightAtten			: TEXCOORD5;
	float3 vAmbient				: TEXCOORD6;
};

float3 CubeUV( float3 vWorldPosition, float3 vWorldNormal, float3 vUVSpacePos )
{
	// Generate texcoords for a cubemap wrapped around the ice sculpture's bounding box
	float3 vDir = normalize( lerp( normalize( vUVSpacePos.xyz ), vWorldNormal.xyz, 0.5 ) );
	float3 tMins = ( g_vBBMin - vWorldPosition ) / vDir;
	float3 tMaxs = ( g_vBBMax - vWorldPosition ) / vDir;
	tMaxs = max( tMaxs, tMins );	// weed out negative t's per axis
	float t = min( tMaxs.x, min( tMaxs.y, tMaxs.z ) );
	float3 vIntersectionPos = vWorldPosition + t * vDir;
	// transform into unit cube
	float3 vCubeUV = vIntersectionPos;
	vCubeUV -= 0.5*( g_vBBMax + g_vBBMin );
	vCubeUV /= 0.5*( g_vBBMax - g_vBBMin );
	vCubeUV = normalize( vCubeUV );
	return vCubeUV;
}


// Main
VS_OUTPUT main( const VS_INPUT i )
{
	VS_OUTPUT o;

	float4 vObjPosition = i.vPos;
	float4 vObjTangent = i.vTangent;
	float3 vObjNormal;
	DecompressVertex_Normal( i.vNormal, vObjNormal );

	// Transform the position and normal
	float3 vWorldPosition = { 0.0f, 0.0f, 0.0f };
	float3 vWorldNormal   = { 0.0f, 0.0f, 0.0f };
	float3 vWorldTangent  = { 0.0f, 0.0f, 0.0f };
	float3 vWorldBinormal = { 0.0f, 0.0f, 0.0f };
	SkinPositionNormalAndTangentSpace(	SKINNING ? true : false,
										vObjPosition, vObjNormal.xyz, vObjTangent.xyzw,
										i.vBoneWeights, i.vBoneIndices, 
										vWorldPosition, vWorldNormal, vWorldTangent, vWorldBinormal );
	vWorldNormal.xyz   = normalize( vWorldNormal.xyz );

	o.vWorldNormal.xyz = vWorldNormal.xyz;
	o.vWorldPos.xyz    = vWorldPosition.xyz;

	// Transform into projection space
	float4 vProjPosition = mul( float4( vWorldPosition, 1.0f ), cViewProj );
	o.vProjPosition  = vProjPosition;
	o.vWorldNormal.w = vProjPosition.z;
	o.vWorldPos.w    = vProjPosition.w;

	// Seamless texturing UV projections
	float3 vUVSpacePos = vWorldPosition.xyz - g_vUVProjOffset.xyz;
	o.vUV0.xy = g_flUVScale * vUVSpacePos.yz;
	o.vUV0.wz = g_flUVScale * vUVSpacePos.xz;
	o.vUV1.xy = g_flUVScale * vUVSpacePos.xy;

	// Cubemap UV gen
	//o.vCubeUVW.xyz = CubeUV( vWorldPosition, vWorldNormal, vUVSpacePos );

	// Screen-space texcoord
	float2 vScreenPos = float2( 0.5, -0.5 ) * vProjPosition.xy + 0.5 * vProjPosition.w;
	o.vUV1.wz = vScreenPos;

	// Dynamic light attenuation factors
	o.vLightAtten.x = GetVertexAttenForLight( vWorldPosition, 0, true );
	o.vLightAtten.y = GetVertexAttenForLight( vWorldPosition, 1, true );
	o.vLightAtten.z = GetVertexAttenForLight( vWorldPosition, 2, true );
	o.vLightAtten.w = GetVertexAttenForLight( vWorldPosition, 3, true );

	// Ambient light
	o.vAmbient = AmbientLight( vWorldNormal );

	// Closest surface's direction and distance, for contact shadowing
	o.vClosestSurfaceDir.xyz = i.vClosestSurfaceDir.xyz;
	o.vClosestSurfaceDir.w   = length( i.vClosestSurfaceDir.xyz );

	return o;
}