Is Chipmunk overkill for simple collision detection?

Question

I'm working on a game where the physics are very simple. I just need to detect when a ball (point) hits a wall (line segment). There is no gravity, no friction, and the collisions are perfectly elastic.

I've already written collision detection code, but I'm about to make some major changes to the project, so there's an opportunity to replace it all with the Chipmunk physics library. Is this a good idea?

On the one hand, Chipmunk will be more heavily tested and optimized than my own code, and I won't have to do the work of maintaining it.

On the other, maybe Chipmunk will be less performant in my case, since it was designed to support a lot of features I won't be using.

I'm hoping someone more familiar with Chipmunk will spare me the effort of profiling it or reading the code myself to make this determination.

Answer 1

The only real advantage Chipmunk would have here is if you are colliding that ball (or many balls) against many walls as it uses a spatial index to only check the collisions of objects that are near each other. This means that you can scale up to hundreds or thousands of objects without slowing to a crawl, but offers no real advantage if you only have a dozen objects in the scene.

It sounds like what you've implemented so far works just fine for your needs. "If it's not broke don't fix it" is a good rule of thumb here. On the other hand, it would be really easy to implement the same thing in Chipmunk. If you want the experience and the possibility of scalability in return for the hassle of a dependency, go for it I guess.

• Scott (the Chipmunk Physics guy)

Answer 2

I've found Chipmunk to be incrediblly easy to use, I would recommend it to anyone starting a 2D project. I can't answer the performance question without knowing your code. I know it uses a spatial hash for collision determination, it may end up doing less collision tests than your code. (On the other hand if there are a very small number of balls and walls, this may not be an issue).

It is open source, so another possibility would be to use Chipmunk, but remove all the features you don't need - gravity, friction, moments of inertia, etc. Again, it's hard to say this is a good option without knowing exactly what you have already implemented.

Answer 3

It really comes down to what you want it to do. I have not used chipmunk itself, but from what it sounds like I'd say you aren't really in need of a full physics library.

Now, if you have plans to expand it beyond a ball and a wall such that you would have use for the expanded physics, then learning it now on a simple problem now may be a good idea. Overall though, unless you either want to learn the physics library or plan on raising the complexity/number of types of physics calculations, I'd say just do it yourself.