stepx = sign(dx);
stepy = sign(dy);
stepz = sign(dz);

public inline function sign(x:Float) : Int{
   return x < 0 ? -1:1;
}

public inline function compSign(v:Vector4) : Vector4{
   return new Vector4(sign(v.x),sign(v.y),sign(v.z),sign(v.w));
}