///////////////////////////////////////////////////////
// MOTION BLUR FRAGMENT PROGRAM 
// Credits to jonathan for optimization
///////////////////////////////////////////////////////


void main(float4 inPos        : WPOS, //in projection space
          float4 inVtxPos        :TEX0,
          float4 inPrevVtxPos    :TEX1,
                      
          out float4 oColor : COLOR,
          
          uniform samplerRECT screenTex        : TEXUNIT0,
          uniform float2 halfScreenSize)
{
	float2 wpos = inPos.xy;
	float2 p1 = inVtxPos.xy / inVtxPos.w;
	float2 p2 = inPrevVtxPos.xy / inPrevVtxPos.w;
	
	float2 velocity = (p2 - p1) * halfScreenSize;
	
	//Sample into scene texture along motion vector
	const float samples = min( max( 1, ceil( max( abs( velocity.x ), abs( velocity.y ) ) / 2 ) ), 16 );
	const fixed w = 1.0 / samples;  // weight
	const float2 s = velocity / samples; // step
	fixed4 a = 0;
	
	for(float i=0; i<samples; i+=1)
	{
		a += texRECT(screenTex, wpos) * w;
		wpos += s;
	}

	oColor = a;
	//oColor.xy = 0.5 + velocity *0.005;
	//oColor.z = 1;

	//oColor.xyz = (1 + velocity) *0.5;
	
	//oColor = texRECT(screenTex, wpos + velocity);
}