/************************************/
/*     Common shader functions      */
/************************************/

/** Interpolate bilinearly between 2 vectors
*/
inline float3 Interpol(float2 w, float3 bl, float3 br, float3 tl, float3 tr)
{
	float3 x1 = lerp(bl, tl, w.y);
	float3 x2 = lerp(br, tr, w.y); 
	float3 v = lerp(x1, x2, w.x); 

	return v;
}


/** reconstruct world space position
*/
inline float3 ReconstructSamplePos(uniform sampler2D tex,
								   float2 texcoord, 
								   float3 bl, float3 br, float3 tl, float3 tr)
{
	const float eyeSpaceDepth = tex2Dlod(tex, float4(texcoord, 0, 0)).w;
	
	float3 viewVec = Interpol(texcoord, bl, br, tl, tr);
	float3 samplePos = -viewVec * eyeSpaceDepth;

	return samplePos;
}


inline float SqrLen(float3 v)
{
	return v.x * v.x + v.y * v.y + v.z * v.z;
}


inline float2 myreflect(float2 pt, float2 n)
{
	// distance to plane
	float d = dot(n, pt);
	// reflect around plane
	float2 rpt = pt - d * 2.0f * n;

	return rpt;
}


inline float2 myrotate(float2 pt, float angle)
{
	float2 rpt;

	rpt.x = pt.x * cos(angle) - pt.y * sin(angle);
	rpt.y = pt.y * cos(angle) + pt.x * sin(angle);

	//normalize(rpt);
	return rpt;
}