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uniform vec4 uResolution;
uniform vec3 camera[4];

float FOV = camera[0].x;
vec3 Eye=camera[1];
vec3 rot = camera[2];

varying vec3 dirDx; // out
varying vec3 dirDy; // out
varying vec3 from; // out
varying vec2 coord; // out
varying float zoom; // out
varying vec3 dir; // out

// Return rotation matrix
mat3  rotationAngleMatrix(vec3 r)
{
	float cx = cos(radians(r.x));
	float sx = sin(radians(r.x));
	float cy = cos(radians(r.y));
	float sy = sin(radians(r.y));
	float cz = cos(radians(r.z));
	float sz = sin(radians(r.z));
	
	return mat3(cy*cz, cy*sz, -sy,
				 sx*sy*cz-cx*sz, cx*cz+sx*sy*sz, sx*cy,
				 sx*sz+cx*sy*cz, cx*sy*sz-sx*cz, cx*cy );
}

mat3 M = rotationAngleMatrix(rot);

vec3 Up = vec3(sin(radians(rot.z)),cos(radians(rot.z)),0.0);
//vec3 Up = vec3(sin(radians(rot.z)),cos(radians(rot.z)),sin(radians(rot.x)));
//vec3 Up = vec3(sin(radians(rot.z)),cos(radians(rot.z)),sin(radians(rot.x)));

vec3 target;

void main(void)
{

	target = Eye + M * vec3(0.0,0.0,-0.0001);
	
	gl_Position =  gl_ModelViewProjectionMatrix * gl_Vertex;
	coord = (gl_ProjectionMatrix*gl_Vertex).xy;
	coord.x*= uResolution.y/uResolution.x;
	// we will only use gl_ProjectionMatrix to scale and translate, so the following should be OK.
	vec2 ps =vec2(uResolution.x*gl_ProjectionMatrix[0][0], uResolution.y*gl_ProjectionMatrix[1][1]);
	zoom = length(ps);
	from = Eye;
	
	vec3 Dir = normalize(target-Eye);
	
	vec3 up = Up-dot(Dir,Up)*Dir;
	up = normalize(up);
	vec3 Right = normalize( cross(Dir,up));
	dir = (coord.x*Right + coord.y*up )*FOV+Dir;
	dirDy = ps.y*up*FOV;
	dirDx = ps.x*Right*FOV;
}