//
// equation at:
// http://inside.mines.edu/~gmurray/ArbitraryAxisRotation/ArbitraryAxisRotation.html
// creates a rotation matrix about the given vector.
//
function vector_rotation(vector, s){
	if(!vector) throw "vector argument to vector_rotation missing";
	if(!s) throw "angle argument to vector_rotation missing";
	if(s === null || s === undefined) throw "angle argument to vector_rotation missing";
	
    var len = Math.sqrt(vector[0]*vector[0]
                        + vector[1]*vector[1]
                        + vector[2]*vector[2]);

    var u = vector[0]/len;
    var v = vector[1]/len;