Archive for the 'graphics' Category


New paper on procedural animation

This is a longer, journal paper on the Twig procedural animation system, submitted to the new journal IEEE Transactions on Computational Intelligence and AI in Games (full disclosure: I’m an associate editor).  This paper documents a fair amount more than the AIIDE paper, including object manipulation scripting, and a little bit about the authoring tools.


my other blog

I’ve been maintaining a separate blog that’s specifically for Twig, the procedural animation system I’ve talked about a little here.  You can find the blog here.  At the moment, it’s more active than this site because that’s where most of my limited hacking and thinking cycles are going.

The blog also includes pointers to the episodes of a “webcomic” that I’m doing with Twig as a way of testing out features and guiding feature implementation.


Final version of AIIDE paper on procedural animation

This is the revised version of the AIIDE paper on Twig, the procedural animation library I’ve been working on.  I’m going to do a longer journal version of it, so suggestions are very welcome.


Procedural animation paper

Sorry for being off the air for so long.  This is a paper I did for AIIDE on the procedural animation work I’ve been doing.  Unfortunately, rather too much of it was written during a 39 hour plane-trip-gone-bad, so I was pretty seriously sleep deprived when I wrote it.  Comments welcome.

Things are winding down for me at school now, so I should be posting more.  There’s another AI paper coming in a few days.


character physics made easy


One of the annoying problems with wanting to do AI for virtual characters is that those characters can’t really do much without bodies.  But giving them bodies means wading into all that bothersome graphics and physics.  If you’ve ever read a paper on hardcore physics simulation, it’s pretty daunting, especially when you think about trying to run it at frame rate.

Probably the single most useful paper I’ve read this summer has been Thomas Jakobsen’s 2001 GDC paper on Advanced Character Physics in the Hitman engine.  Jakobsen talks about how to implement believable ragdoll physics by basically ignoring angular momentum and modeling rigid and articulated objects as particles (with only linear momentum) connected by rigid constraints.  By using a combination of techniques – Verlet integration and constraint satisfaction by projection – you can make a system that’s easy to implement, runs quite fast, and looks pretty good.  I was able to implement a basic engine in about 800 lines of C# code and an acceptable procedural animation system in another 600 lines or so (I’m particularly proud of the hugging behavior shown above).  It took me about a week of hacking, which is pretty good given that it was only my third 3D graphics program.  I highly recommend Jakobsen’s paper.