The first two args of glutSolidTorus() are the inner
radius and the outer radius. The standard definition
of the inner radius is the distance of the inner wall
of the "donut" from the center of the hole. Similarly
the outer radius is taken to be the distance from the
center of the hole to the outside edge of the "donut".
For these coordinates, the diameter of the torus
looking down the z-axis should be 2*outer radius.
This does not appear to be the implementation
used by freeglut. I don't have the original GLUT
here in order to check whether freeglut is consistent
with the original GLUT.