Transform dir_trans = Transform::rotation(dir, Vector(0, 0, 1));
if(radius)
{
Angle a = Angle::from_radians(d/radius);
Vector r = dir_trans.transform(Vector(0, -radius, 0));
Transform dir_trans = Transform::rotation(dir, Vector(0, 0, 1));
if(radius)
{
Angle a = Angle::from_radians(d/radius);
Vector r = dir_trans.transform(Vector(0, -radius, 0));