The ring object
is circular, with a specified outer radius and thickness, and with its center
given by the pos attribute:
The ring object has attributes pos, x, y, z, axis, length, color, red, green, blue, and up like those for cylinders. As with cylinders, up has a subtle effect on the 3D appearance of a ring. The axis attribute only affects the orientation of the ring; the magnitude of the axis attribute is irrelevant. Additional ring attributes:
radius Outer radius of the ring
thickness Thickness of ring (1/10th of radius if not specified)
Note that the pos attribute for cylinder, arrow, and cone corresponds to one end of the object, whereas for a ring and a sphere it corresponds to the center of the object.