// Vertex program for fresnel reflections / refractions
void main_vp(
		float4 pos			: POSITION,
		float4 normal		: NORMAL,
		float2 tex			: TEXCOORD0,
		
		out float4 oPos		: POSITION,
		out float fresnel   : COLOR,
		out float3 noiseCoord : TEXCOORD0,
		out float4 projectionCoord : TEXCOORD1,

		uniform float4x4 worldViewProjMatrix,
		uniform float3 eyePosition, // object space
		uniform float fresnelBias,
		uniform float fresnelScale,
		uniform float fresnelPower,
		uniform float timeVal,
		uniform float scale,  // the amount to scale the noise texture by
		uniform float scroll, // the amount by which to scroll the noise
		uniform float noise  // the noise perturb as a factor of the  time
		)
{
	oPos = mul(worldViewProjMatrix, pos);
	// Projective texture coordinates, adjust for mapping
	float4x4 scalemat = float4x4(0.5,   0,   0, 0.5, 
	                               0,-0.5,   0, 0.5,
								   0,   0, 0.5, 0.5,
								   0,   0,   0,   1);
	projectionCoord = mul(scalemat, oPos);
	// Noise map coords
	noiseCoord.xy = (tex + (timeVal * scroll)) * scale;
	noiseCoord.z = noise * timeVal;

	// calc fresnel factor (reflection coefficient)
	float3 eyeDir = normalize(pos.xyz - eyePosition);
	fresnel = fresnelBias + fresnelScale * pow(1 + dot(eyeDir, normal), fresnelPower);
	
}

// Fragment program for distorting a texture using a 3D noise texture
void main_fp(
		float fresnel				: COLOR,
		float3 noiseCoord			: TEXCOORD0,
		float4 projectionCoord		: TEXCOORD1,
		
		out float4 col		: COLOR,
		
		uniform float distortionRange,
		uniform float4 tintColour,
		uniform sampler3D noiseMap,
		uniform sampler2D reflectMap,
		uniform sampler2D refractMap
		)
{
	// Randomly chosen offset for y noise sample
	float3 yoffset = float3(0.31, 0.58, 0.23);
	float2 distort;
	// Sample the noise texture at 2 places
	distort.x = tex3D(noiseMap, noiseCoord).x;
	distort.y = tex3D(noiseMap, noiseCoord + yoffset).x;
	// Scale the distortion from [0,1] to [-range,range]
	distort = (distort * 2 - 1) * distortionRange;

	// Do the tex projection manually so we can distort _after_
	float2 final = projectionCoord.xy / projectionCoord.w;
	final += distort;
	
	float4 reflectionColour = tex2D(reflectMap, final);
	float4 refractionColour = tex2D(refractMap, final) + tintColour;
	col = lerp(refractionColour, reflectionColour, fresnel);


}