See section 12.14.5 for homotheties in space.
A homothety is a dilation about a given point. The homothety command can take two or three arguments.
If homothety has two arguments, they are a point (the center
of the homothety) and a real number (the scaling ratio).
homothery returns a new command which performs the dilation.
If homothety has three arguments, the first two arguments are a
point and real number as above, and the third argument is a geometric
object. homothety returns and draws the dilated object.
The homothety command can also take a complex number as the second argument. In that case, the result will be a rotation as well as a dilation.