*Updated October 14, 2008*

Every once in a while I’m asked by Midway Home Entertainment to perform motion capture for the Mortal Kombat games due to my martial arts experience. Today was one such day, and I thought it would be interesting to some of my readers to know what that entails.

When I arrive at the office in the morning, I usually head straight to the motion capture studio. If I am early, I might drop in on some of my friends and chat a bit. Once in the studio, I suit up while the motion capture team set up and calibrate the system.

For those not familiar with motion capture, according to wikipedia

Motion capture, motion tracking, or mocap is a technique of digitally recording movements for entertainment, sports, and medical applications. In the context of filmmaking (where it is sometimes called performance capture), it refers to the technique of recording the actions of human actors, and using that information to animate digital character models in 3D animation.

The motion capture talent is suited up in a tight black outfit with many small reflective markers velcro-ed onto them. Cameras or sensors around the room pick up the position of these markers and record the data into the motion capture software. By recording human movement this way and applying them to 3D models, you can get much better and more natural movement for much cheaper than you could if you were to use key framing.

Once I suit up, I help one of the guys put all the reflective markers on me. You might think that the markers go on joints but in actuality, placing them on joints makes the data less meaningful because you can’t detect joint rotation as well. So the markers generally go between joints like forearms, biceps, shins, etc. I’ll start warming up by doing some wushu basics, jogging, and some stretching.

When we’re ready to begin, they’ll do a “range of motion” test. I stand in the middle of the capture space and do things like lift my arms up, bend my elbows, bend my knees, swing my arms around, kick, bend my neck, and move around. I’ll talk with the team and try to understand what they want us to do. Usually there’s 2 or 3 motion capture artists at any one shoot. Today it was Carlos, Ray Wu, and I. Once I get what they want me to do, if it’s a cinematic intro, we’ll come up with a sequence on the spot given the direction and rehearse it a couple of times before we shoot. We’ll shoot until lunch at which point some of the people I know might drop in the capture studio to chat while we eat. After lunch we resume shooting until end of day.

On this particular day, Ray did a flash kick as part of a move. Mostly we shot some in-game moves. One thing to note is that for each sequence, we start in a T-pose and end in it. A T-pose helps map our motion capture skeleton to the 3D character they’ll map to. Motion capture is a fun and cool experience. It’s neat to see your moves mapped to a stick figure in real-time during the capture session and also to see it in the actual game.

* Sachin Agarwal, CEO of Dawdle.com has a good write up of another one of my motion capture sessions at Midway Games over at the Dawdle blog.

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