There is no gluGetBounds function, but since *you* have to provide some parameters to those functions to descibe the size of the object (the radius parameter in gluSphere for example), it stands to reason that you already know the size of the object before you create it. Therefore, you can easily compute the bounds of the object. For example, a sphere with radius x will be contained in a box of with a width of 2*x, a height of 2*x, and a depth of 2*x. A cylinder with radius x and height y can be contained in a box of size 2x * 2x * y. Just imagine the shape of the object and you should be able to create a bounding box for it. Sketching it out on paper may make it more apparent.