#include "common_vs_fxc.h"

//---------------------------------------------------------------------------------//
// Parallax occlusion mapping algorithm implementation. Vertex shader.             
//---------------------------------------------------------------------------------//


#define matWorldViewProjection cModelViewProj
//float4x4 matViewInverse;
//float4x4 matView;

//float    fBaseTextureRepeat;
//float4   vLightPosition;

struct VS_INPUT
{
	float4 positionWS  : POSITION;
	float3 vNormalWS   : NORMAL;
	float2 texCoord    : TEXCOORD0;
	float3 vBinormalWS : BINORMAL;
	float3 vTangentWS  : TANGENT;
};

struct VS_OUTPUT
{
	float4 position          : POSITION;	// proj-space position
	float2 texCoord          : TEXCOORD0;
//	float3 vLightTS          : TEXCOORD1;   // light vector in tangent space, denormalized
	float3 vViewTS           : TEXCOORD2;   // view vector in tangent space, denormalized
	float2 vParallaxOffsetTS : TEXCOORD3;   // Parallax offset vector in tangent space
	float3 vNormalWS         : TEXCOORD4;   // Normal vector in world space
	float3 vViewWS           : TEXCOORD5;   // View vector in world space
	float4 vDebug		     : TEXCOORD6;
};

VS_OUTPUT main( VS_INPUT i )
{
	VS_OUTPUT Out = (VS_OUTPUT) 0;

	// Transform and output input position 
	Out.position = mul( float4( i.positionWS.xyz, 1 ), cModelViewProj );
	//Out.position = mul( matWorldViewProjection, i.positionWS );

	// Propagate texture coordinate through:
	Out.texCoord = i.texCoord; 

	// Uncomment this to repeat the texture 
	// Out.texCoord *= fBaseTextureRepeat;

	// Propagate the world vertex normal through:   
	Out.vNormalWS = i.vNormalWS;

	// Compute and output the world view vector:
	float3 vViewWS = cEyePos - i.positionWS;
	Out.vViewWS = vViewWS;

	// Compute denormalized light vector in world space:
//	float3 vLightWS = vLightPosition - i.positionWS;

	// Normalize the light and view vectors and transform it to the tangent space:
	float3x3 mWorldToTangent = float3x3( i.vTangentWS, i.vBinormalWS, i.vNormalWS );
//	float3x3 mWorldToTangent = float3x3( i.vBinormalWS, i.vTangentWS, i.vNormalWS );

	// Propagate the view and the light vectors (in tangent space):
//	Out.vLightTS = mul( mWorldToTangent, vLightWS );
	Out.vViewTS  = mul( mWorldToTangent, vViewWS  );

	float fHeightMapRange = 0.02f; // FIXME: should be a vmt param

	// Compute the ray direction for intersecting the height field profile with 
	// current view ray. See the above paper for derivation of this computation.

	// Compute initial parallax displacement direction:
	float2 vParallaxDirection = normalize(  Out.vViewTS.xy );

	// The length of this vector determines the furthest amount of displacement:
	float fLength = length( Out.vViewTS );
	float fParallaxLength = sqrt( fLength * fLength - Out.vViewTS.z * Out.vViewTS.z ) / Out.vViewTS.z; 

	// Compute the actual reverse parallax displacement vector:
	Out.vParallaxOffsetTS = vParallaxDirection * fParallaxLength;

	// Need to scale the amount of displacement to account for different height ranges
	// in height maps. This is controlled by an artist-editable parameter:
	Out.vParallaxOffsetTS *= fHeightMapRange;

	Out.vDebug = float4( 1.0f, 0.0f, 0.0f, 1.0f );
	Out.vDebug.xy = vParallaxDirection;
	//   Out.vDebug.xyz = ( float3 )fHeightMapRange;
	Out.vDebug.xyz = fParallaxLength * .1;
	Out.vDebug.xyz = fHeightMapRange * 200;

	return Out;

}   // End of VS_OUTPUT vs_main(..)