April 1st, 2013| Posted by slembcke
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We had a great time at GDC last week! We ended up meeting a lot of new and interesting people. It’s always great because we can chat with a lot of people who are and are not using Chipmunk to figure out how we can make it even better.

Farewell Chipmunk Physics. Long Live Chipmunk2D!

Chipmunk isn’t going anywhere. Just rebranding a little bit to make it easier to search for. Google for “Chipmunk” and see how much of it is physics related. 😉

This was a suggestion that came up a bit before GDC in a Cocos2D thread, but came up a couple times more when there.

On that note, I’ve set up a new URL, chipmunk2d.net (currently just a redirect), and a new twitter account @chipmunk2d dedicated to Chipmunk stuff. Follow us and help spread the word!

Unity3D support:

I was never quite sure how to make Chipmunk fit in nicely with Unity, so it’s been an idea that sat on the very back burner. After talking with people at GDC, there definitely seems to be a nice niche market for a good 2D physics engine. It seems a lot of people are frustrated trying to get the builtin 3D physics to do 2D nicely. I think with a bunch of custom editor components we can get something pretty close to the simplicity Unity provides now and then sprinkle in some of our own secret Chipmunk sauce to make it even better.

Chipmunk provides a number of nice features that PhysX does not (or at least are not exposed). Since Chipmunk isn’t doing all that extra work for a dimension that is just being thrown away it’s also *much* faster. So we think we can go simpler, faster, and more flexible. Seems like a win/win/win scenario if you want to do 2D physics games.

Better JS Support:

Last year, Joseph Gentle made a fantastic port of Chipmunk to Javascript. He’s also done a great job so far of keeping it up to date so far. I don’t do much Javascript myself, but it’s become so much better recently that I’m excited for the possibilities! I’d love to put some interactive stuff on the Chipmunk website and in the documentation.

Anyway, with Chipmunk-JS becoming a more or less standard part of Cocos2D-JS, I’m going to try and make timely patches for Joseph so he’s not stuck volunteering to port all my changes and fixes.

Simplify Simplify Simplify!

One of my design goals with Chipmunk is to keep the API as simple as it can be without taking away flexibility. I’ve spent a lot of time thinking about how to avoid thresholds, sensitivity to units and other “tuning” factors. I’ve gotten some very nice compliments on it’s simplicity, so I think I’ve probably done OK in that regard. It could be better though! You shouldn’t need to be a physics engine master to make great games using one. Sometimes I lose sight of what it’s like to be a beginner. I’ve got two particular cases in mind. Simplified object creation and a collision only mode.

Creating a physics object in Unity or Box2D is different than Chipmunk. You lay out your collision shapes and they guess the mass, center of gravity and moment of inertia for you. This takes away some flexibility, but it’s also vastly simpler for beginners. I have utility functions in Chipmunk to help out with that, but sometimes people don’t care or need to know what a moment of inertia is to make a good game. It’s just a barrier that gets in their way.

A lot of people want to make a game that needs collision detection, but don’t really care about physics. It’s perfectly possible to do that with Chipmunk now, but it’s certainly not obvious how for a beginner. I could totally build a simpler API on top of Chipmunk to help with this.

Continuous Collision Detection (CCD):

This is related to the previous point. I’ve tried to make Chipmunk’s API as simple as possible and make it so that things “just work” without having to fiddle with thresholds and scales and such. One thing that doesn’t “just work” in Chipmunk is continuous collision detection. I usually sort of brush it off as being unecessary or usually very easy to work around, which is true, but missing my own point. Collisions should “just work” and not be something that you need to worry about as a designer. Erin Catto made that point in his GDC talk on collision detection, and it really struck a chord. The 6.2 beta branch is already a big step in the right direction.

I’ve been sitting on some ideas for mixing pseudo-velocities and speculative contacts for some time. I think it could work really well and solve some of the things I didn’t initially like about speculative contacts. If it works well, it will be awesome. 😀 If not… then I’ll have to go with something more traditional. 🙁

More Tutorial Content:

Documentation, examples, tutorials… There can never be enough! I try to make as much as I can, but it’s very time consuming to do. I met up with Ray Wenderlich and Rod Strougo (They wrote the book “Learning Cocos2D”) at GDC and they sounded pretty interested in working with us to make more of it and get it out where people can see it. They are pretty active in the books and documentation realms, so I think that can be a great asset.

Great. Can you have it done by Friday?

Oof. So clearly that is a lot of stuff to chew on. Our company mostly supports itself by doing contracting work, but we’ve scheduled a big block of time for enhancing Chipmunk for a while. If there’s something you’re really dying to have in Chipmunk, let me know. It’s good to have some external input when prioritizing.

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