///////////////////////////////////////////////////////////////////////////
//
//		vertex program used to render the particles.
//		sets the particle position reading from the position texture
//		and stretches the particle onscreen.
//
///////////////////////////////////////////////////////////////////////////



struct entree
{
	float4 position : POSITION;
	float4 texCoords0 : TEXCOORD0;
};

struct sortie
{
	float4 position    : POSITION;
	float2 texCoords0  : TEXCOORD0;
	float2 texCoords1  : TEXCOORD1;
	float4 posworld    : TEXCOORD2;
	float4 normale     : TEXCOORD3;
	float3 eyetovert   : TEXCOORD4;
};



#define SCREEN_RATIO		(1280.0/1024.0)

sortie mainNoStreaks(entree IN,
                     uniform float3 viewPos,
                     uniform float3 viewDir,
                     uniform float3 boxMin,
                     uniform float3 boxMax,
                     uniform float rainBbSide,
                     uniform float4x4  worldviewproj,
                     uniform float4x4  worldview,
                     uniform sampler2D texPos : TEXUNIT1)
{
	sortie OUT;
	
	//we get the position of the vertex from the texture
	
	float4 posFromTexture = tex2D(texPos, IN.texCoords0.zw);
	
	float4 thePos;
	thePos.x = viewPos.x + posFromTexture.x * (boxMax.x - boxMin.x) + boxMin.x - viewDir.x * ((boxMax.x - boxMin.x) / 2.0);
	thePos.y = viewPos.y + posFromTexture.y * (boxMax.y - boxMin.y) + boxMin.y;
	thePos.z = viewPos.z + posFromTexture.z * (boxMax.z - boxMin.z) + boxMin.z - viewDir.z * ((boxMax.z - boxMin.z) / 2.0);
	thePos.w = 1.0;
	
	// USE FOLLOWING LINE TO AVOID READING POSITION FROM TEXTURE
	//float4 thePos = IN.position + 0.000000001 * (viewPos.x + boxMax.x + boxMin.x + viewDir.x);
	
	// transform it to screen space
	OUT.position = mul(worldviewproj, thePos);
	
	// shape it as a quad (oriented on camera plane)
	OUT.position.x += rainBbSide * (IN.texCoords0.x - 0.5f);
	OUT.position.y -= rainBbSide * SCREEN_RATIO * (IN.texCoords0.y - 0.5f);


	// don't change the fist texture coordinates
	OUT.texCoords0 = IN.texCoords0.xy;
	
	// second texture coordinates receive the position of the drop, in screen space
	float4 VposEye = mul(worldviewproj, thePos);
	VposEye.xyz /= VposEye.w;	
    OUT.texCoords1 = (1.0 + VposEye.xy).xy / 2.0;
	OUT.texCoords1.y = 1.0 - OUT.texCoords1.y;
	
	OUT.normale.x = (IN.texCoords0.x - 0.5) * 2.0;
    OUT.normale.y = -(IN.texCoords0.y - 0.5) * 2.0;
	OUT.normale.zw = 1.0;
	
	OUT.posworld = thePos; // unprojected vertex coordinate
	OUT.eyetovert = mul(worldview, thePos).xyz;
	
	return OUT;
}






sortie mainStreaks(entree IN,
                   uniform float3 viewPos,
                   uniform float3 viewDir,
                   uniform float3 boxMin,
                   uniform float3 boxMax,
                   uniform float3 fallVect,
                   uniform float rainBbSide,
                   uniform float streaksHeight,
                   uniform float4x4  worldviewproj,
                   uniform float4x4  worldview,
                   uniform sampler2D texPos : TEXUNIT1)
{
	sortie OUT;
	
	  
	//we get the position of the vertex from the texture
	float4 posFromTexture = tex2D(texPos, IN.texCoords0.zw);
	float4 thePos;
	thePos.x = viewPos.x + posFromTexture.x * (boxMax.x - boxMin.x) + boxMin.x - viewDir.x * ((boxMax.x - boxMin.x) / 2.0);
	thePos.y = viewPos.y + posFromTexture.y * (boxMax.y - boxMin.y) + boxMin.y;
	thePos.z = viewPos.z + posFromTexture.z * (boxMax.z - boxMin.z) + boxMin.z - viewDir.z * ((boxMax.z - boxMin.z) / 2.0);
	thePos.w = 1.0;
	
	// USE FOLLOWING LINE TO AVOID READING POSITION FROM TEXTURE
	//float4 thePos = IN.position + 0.000000001 * (viewPos.x + boxMax.x + boxMin.x + viewDir.x);
	
// stetch the streak vertically
	thePos.y += (1.0 - IN.texCoords0.y) * streaksHeight;
// make it follow the wind direction
	thePos.xz += (IN.texCoords0.y * 2.0 - 1.0) * fallVect.xz;
// transform its coordinate to screen space
	OUT.position = mul(worldviewproj, thePos);
	
	// shape it as a quad (oriented on camera plane)
	OUT.position.x += rainBbSide * (IN.texCoords0.x - 0.5f);


// don't change the first texture coordinates
	OUT.texCoords0 = IN.texCoords0.xy;
	
	float4 VposEye = OUT.position;
	VposEye.xyz /= VposEye.w;
	OUT.texCoords1 = (1.0 + VposEye.xy).xy / 2.0;
	OUT.texCoords1.y = 1.0 - OUT.texCoords1.y;
	
	OUT.normale.x = (IN.texCoords0.x - 0.5) * 2.0;
	OUT.normale.y = -(IN.texCoords0.y - 0.5) * 2.0;
	OUT.normale.zw = 1.0;
	
	OUT.posworld = thePos;
	OUT.eyetovert = mul(worldview, thePos).xyz;
	
	return OUT;
}