This isn’t exactly an OpenGL question, but I know a lot of the people here have poked around with game engines, so I thought maybe someone had run into this before.
As indicated, I’m working on a physics engine in C++. I want to be able to build a tree of bounding volumes for my objects and test intersections between these bounding volumes. I would also like to be able to use different types of volumes in the same tree (i.e. bounding spheres and bounding boxes in the same tree). I’m an experienced C++ programmer, so this is a rather embarrassing question, but I can’t figure out a good way to do this!
My initial thought was to have Sphere and Box classes. Of course, to stick them in the same tree, they’ll both have to have a common base class. When I test for pairwise overlaps through the base class is where the problems come up. For instance, suppose I have two tree nodes, node1 and node2. What I would like to have is a boolean function that returns whether they overlap. Like node1.testOverlap(node2). It doesn’t have to be a member function, though, I would be happy with testOverlap(node1, node2).
Here’s my question: If the testOverlap function is a member of the derived classes, it must be present in the base class as a virtual function. Unfortunately, this requires me to put references to Box and Sphere in the base class…I think it’s bad programming practice to have a base class have to “know” about all classes derived from it.
If the testOverlap(a,b) function is not a member (the solution I’d prefer), then I don’t think I can call it from a base class pointer, can I? For instance, I couldn’t call testOverlap(node1, node2) and have it realize node1 is a sphere and node2 is a sphere so it should really call testOverlap(sphere, sphere).
It seems like some of you may have run into a problem like this in the past. If so, or if you have an idea for an elegant solution, I’d really like to hear it. I’m really hoping I don’t have to have a type identifier in each class or do something kludgy like that.