I recently implemented a version which works very well for me. The support map function is used to build a triangle mesh. And the triangle mesh is then used to get the inertia.
Have a look here: http://code.google.com/p/jitterphysics/ ... s/Shape.cs
MakeHull() and CalculateMassInertia() are the functions of interest. In all my test cases the inertia was nearly the same as the analytical value. The problem is that Iam not sure about "convergence/correctness" of the Hull making function. I recently (5min ago) contacted the original author of this function to get more information. The CalculateMassInertia function is then just a simple method based on an idea descriped here: www.number-none.com/blow/inertia/bb_inertia.doc
(yeah, *.doc format!)