Behavior Trees for Next-Gen Game AI (Video, Part 1)

Alex J. Champandard on December 12, 2007

Quite a few people asked for a PDF of my slides from my lecture at the GDC in Lyon, but I promised to do better and release a video with the animations an the whole audio. Here is the first part of the talk; it’s exactly 22:37 minutes long.

In the video, I go over the motivation for behavior trees, in particular how they relate to other techniques using hierarchical logic and what problems they address. I also give a quick introduction of the concepts behind behavior trees using a simple guard dog example that you should be familiar with if you’ve been following the tutorial series here on

It took much longer than expected to prepare, but at least I’m a little more comfortable with video editing tools now! The second part will be posted this Sunday, and is reading for being edited… Be sure to subscribe to be notified when it’s released.

Discussion 7 Comments

Dave Mark on December 13th, 2007

Hell, it takes longer than 22 minutes to download the bloody thing! That's a whopper, Alex!

alexjc on January 4th, 2008

Well, it seems the video has trouble loading under internet explorer. If I use Javascript, it works out ok in IE 6/7. But when I do, then it gets messed up in feed readers... In the future, I'll use a forum to provide high-quality videos that registered members can download freely :-)

Crash on March 21st, 2008

Hi Alex, I am also having difficulty viewing the videos on the blog. Have you already uploaded them somewhere else for download? I am very keen to see this material. Sam,

dannyBlue on March 21st, 2008

where can i find the video?

Crash on March 22nd, 2008

The video is at: [url][/url] I don't know if alex's announcement today about videos in the other forum was in refrence to this but it worked ok for me today. Very informative and I look forward to watching the others soon.

kofman on May 9th, 2008

Incredibly informative. Myself, being totally inexperienced with HTN Planners and the like, I walked away with a great understanding of Behavior Trees after watching this video. About to move onto the next two.

jadnohra on July 12th, 2008

before I jump into part2, this is the first time I see a way of 'piping' all those pieces of logic that actually do sthg (called conditions and actions here), in a really convenient way ... the concept of forcing a task to either fail or succeed and nothing else is great, it forces you to build the complexity around the behavior tree's structure, thus forcing you to make actions and conditions that are really pluggable. add the way the tree is executed using selectors and sequences, this makes it definitely a sensible 'structure' that removes the fear of things breaking down at every small unexpected event. I was always grumpy about all the other solutions, this is the first one that makes me intuitively think, mmm this might be it. so thx for introducing / sharing!

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