public static float AngleVectorPlane(Vector3 vector, Vector3 normal)
{
float dot;
float angle;
//calculate the the dot product between the two input vectors. This gives the cosine between the two vectors
dot = Vector3.Dot(vector, normal);
//this is in radians
angle = (float)Math.Acos(dot);
return 1.570796326794897f - angle; //90 degrees - angle
}