public float distanceBetweenVectors( SimpleVector a, SimpleVector b ){ return (float) Math.sqrt( (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y) + (a.z-b.z)*(a.z-b.z) );}
s1.calcSub(s2).length();