Changing gravity

Yes, I found the resource on modifying gravity via scripting for individual players, but I need something a little bit different. I would like to change the gravity from going one direction (i.e. along the z axis) to coalesce at a single point. Imagine a small planet (like a tennis ball) that has an enormous amount of gravity and attracts everything to it.

Now, the problem I have is I can't for the life of me find where the gravity attributes are actually used. I found member variables inside ShapeBase and such about gravity, but not a single function uses them, as far as I can see. Can someone tell me where such data is used in the engine?

Thanks.