Another improvement to this method is to use multiple types of approximation techniques together.
When the fast one catches up to the slow one, it will pass through it and come out in front of it.
A screenshot of the program running is below: objects for each of the meshes in the model.
We will focus on bounding spheres in this tutorial, because of their simplicity, and because XNA has a lot of built in support for bounding spheres.
The basic idea is that for each model you are using, or for each mesh in a model, you will construct a sphere from it.
One drawback to this method is that a sphere (or even a bounding box) may not be a good approximation for an object.
For instance, imagine you have a long object, like the arrow in the image below.
With these methods, you would basically build a box or sphere around a model that completely covers the model.
There will obviously be area that is outside of the model, but still inside of the bounding box or sphere, but an ideal bounding region will limit this as much as possible.
It is important to know when objects in a game collide.