HTTP/2 301 server: nginx date: Tue, 27 Jan 2026 04:04:37 GMT content-type: text/html content-length: 162 location: https://ianhorswill.wordpress.com/feed/ x-ac: 2.bom _dca MISS alt-svc: h3=":443"; ma=86400 strict-transport-security: max-age=31536000 server-timing: a8c-cdn, dc;desc=bom, cache;desc=MISS;dur=231.0 HTTP/2 200 server: nginx date: Tue, 27 Jan 2026 04:04:37 GMT content-type: application/rss+xml; charset=UTF-8 vary: Accept-Encoding x-hacker: Want root? Visit join.a8c.com/hacker and mention this header. host-header: WordPress.com vary: accept, content-type last-modified: Wed, 28 May 2025 17:18:49 GMT x-nc: HIT dca 30 content-encoding: gzip x-ac: 4.bom _dca BYPASS alt-svc: h3=":443"; ma=86400 strict-transport-security: max-age=31536000 server-timing: a8c-cdn, dc;desc=bom, cache;desc=BYPASS;dur=234.0 https://ianhorswill.wordpress.com artificial intelligence, robotics, and interactive entertainment Tue, 26 Mar 2013 23:55:26 +0000 en hourly 1 https://wordpress.com/ https://s0.wp.com/i/buttonw-com.png https://ianhorswill.wordpress.com https://ianhorswill.wordpress.com/2013/03/26/how-to-build-a-constraint-propagator-in-a-weekend/ https://ianhorswill.wordpress.com/2013/03/26/how-to-build-a-constraint-propagator-in-a-weekend/#comments Tue, 26 Mar 2013 23:55:26 +0000 https://ianhorswill.wordpress.com/?p=45 This is a tutorial that Leif Foged and I did for the AI summit at GDC on how to build your own finite-domain constraint solver using AC-3.  It’s won’t solve the really hard problems that high-end SAT solvers can solve, but it’s very fast for problems with a lot of solutions; fast enough to run in a game engine:

      https://www.cs.northwestern.edu/~ian/GDCConstraintsHowTo.pdf

Comments welcome.  I intend to keep revising it, since it isn’t archivally published.

 

]]> https://ianhorswill.wordpress.com/2013/03/26/how-to-build-a-constraint-propagator-in-a-weekend/feed/ 10 ian https://ianhorswill.wordpress.com/2009/01/12/new-paper/ https://ianhorswill.wordpress.com/2009/01/12/new-paper/#respond Mon, 12 Jan 2009 18:34:23 +0000 https://ianhorswill.wordpress.com/2009/01/12/new-paper/ 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.

]]> https://ianhorswill.wordpress.com/2009/01/12/new-paper/feed/ 0 ian https://ianhorswill.wordpress.com/2009/01/12/new-paper-comments-welcome/ https://ianhorswill.wordpress.com/2009/01/12/new-paper-comments-welcome/#comments Mon, 12 Jan 2009 18:18:24 +0000 https://ianhorswill.wordpress.com/2009/01/12/new-paper-comments-welcome/ This is a paper I wrote for ICFDG that takes some work from my previous life as a roboticist and applies it to Twig (the procedural animation system I’ve been working on).  However, it’s situated in a tradition that the games community, and even the present-day AI community isn’t very familiar with, so much of the paper is an attempt to survey and explain the literature on using combinational logic for inference – why you’d want to do it, why it’s limited, and what you can do to overcome some of the limitations.  And even then, I’m worried that it won’t be transparent to the reader; not because it’s technically difficult, but just because the motivations won’t be clear.  Anyhow, any advice would be welcome.

]]> https://ianhorswill.wordpress.com/2009/01/12/new-paper-comments-welcome/feed/ 1 ian https://ianhorswill.wordpress.com/2008/11/09/fall-symposium-talk-slides/ https://ianhorswill.wordpress.com/2008/11/09/fall-symposium-talk-slides/#respond Sun, 09 Nov 2008 01:53:24 +0000 https://ianhorswill.wordpress.com/2008/11/09/fall-symposium-talk-slides/ Here are the slides from my position paper at the AAAI Fall Symposium on Naturally Inspired Artificial Intelligence.

]]> https://ianhorswill.wordpress.com/2008/11/09/fall-symposium-talk-slides/feed/ 0 ian https://ianhorswill.wordpress.com/2008/10/27/the-passing-of-a-friend/ https://ianhorswill.wordpress.com/2008/10/27/the-passing-of-a-friend/#comments Mon, 27 Oct 2008 23:14:14 +0000 https://ianhorswill.wordpress.com/2008/10/27/the-passing-of-a-friend/  

 

My friend Patrick Welch, a painter, comic artist, and professor at the Illinois Institute of Art, passed away recently.  He will be greatly missed.  Drink a beer for him for me.

]]> https://ianhorswill.wordpress.com/2008/10/27/the-passing-of-a-friend/feed/ 2 ian Patrick 1 image image https://ianhorswill.wordpress.com/2008/10/25/my-other-blog/ https://ianhorswill.wordpress.com/2008/10/25/my-other-blog/#respond Sat, 25 Oct 2008 02:44:29 +0000 https://ianhorswill.wordpress.com/2008/10/25/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.

]]> https://ianhorswill.wordpress.com/2008/10/25/my-other-blog/feed/ 0 ian https://ianhorswill.wordpress.com/2008/08/19/final-version-of-aiide-paper-on-procedural-animation/ https://ianhorswill.wordpress.com/2008/08/19/final-version-of-aiide-paper-on-procedural-animation/#comments Tue, 19 Aug 2008 20:10:07 +0000 https://ianhorswill.wordpress.com/2008/08/19/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.

]]> https://ianhorswill.wordpress.com/2008/08/19/final-version-of-aiide-paper-on-procedural-animation/feed/ 5 ian https://ianhorswill.wordpress.com/2008/06/01/another-paper/ https://ianhorswill.wordpress.com/2008/06/01/another-paper/#respond Sun, 01 Jun 2008 11:59:16 +0000 https://ianhorswill.wordpress.com/2008/06/01/another-paper/ Men are Dogs (and Women too).  This one’s for the AAAI Fall Symposium on Natural Computation.  It’s my latest effort to try to get my intuitions about cognitive architecture onto paper.  There are a bunch of other arguments that I want to fold into it, but it’s already overdue, so they’ll have to wait for the camera ready copy.  Comments and suggestions welcome.

]]> https://ianhorswill.wordpress.com/2008/06/01/another-paper/feed/ 0 ian https://ianhorswill.wordpress.com/2008/05/26/procedural-animation-paper/ https://ianhorswill.wordpress.com/2008/05/26/procedural-animation-paper/#comments Mon, 26 May 2008 01:07:33 +0000 https://ianhorswill.wordpress.com/2008/05/26/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.

]]> https://ianhorswill.wordpress.com/2008/05/26/procedural-animation-paper/feed/ 1 ian https://ianhorswill.wordpress.com/2008/01/24/coming-up-for-air/ https://ianhorswill.wordpress.com/2008/01/24/coming-up-for-air/#respond Thu, 24 Jan 2008 02:29:42 +0000 https://ianhorswill.wordpress.com/2008/01/24/coming-up-for-air/ Last quarter I was teaching 3 classes, so I’m just getting my head above water now.  I’ll try to start posting regularly again now.  I’ve gotten at least a little bit of hacking done and should have a pre-alpha release of the humanoid animation code in time for GDC.

]]> https://ianhorswill.wordpress.com/2008/01/24/coming-up-for-air/feed/ 0 ian