Mark Wilson's Blog

Biorobots, more and more

Attended an ACM event tonight on animation. Not a lot of what was said was in any way directly applicable to what I'm doing for EMAE/BIOL 377, since the talk centered around Maya (a pre-authored, high-powered, but ungodly expensive animation tool), but it was a good event in that it got me thinking about some issues I'm going to have to deal with in using keyframed animation.

It's good to think about issues now, because I finally got around to reading in keyframes and hopping from one to the next in the program this past weekend, and most of these issues are the next big step. I don't want to get up to my neck in code and then realize I've done something stupid and have to redo it all.

The big one, of course, is going to be interpolation, which I had kind of been dealing with up to this point by making mystic passes at it and chanting. Linear interpolation is simple, obviously, but there's no way on God's green earth that it will ever look right. Interpolating correctly is likely going to involve some calculus of one sort or another, and I need to figure out a way to specify an interpolation function as part of each keyframe's specification, just as I'm currently specifying a relative duration to the next keyframe.

Maya uses a simple system (from the user's point of view) wherein you can attach handles, tangential to the curve, at any point along the graph of the interpolated frames and use them to alter the curve's rate of change around that point, via a fairly intuitive system of rotating the handles around the point. It probably sounds complicated, but when you're looking at it graphically it's very obvious. I haven't thought too hard about this yet, but I'm wondering if there's some way to specify a similar set of rate-of-change modifiers in plaintext and use that to make some simple alterations to the rate of change between keyframes.

Or is there a better (simpler) way? I'm not quite sure yet. Probably need to consult some references.

Now to find time between my other assignments to work on fun, challenging stuff like this. Programming some wacky stuff for Theoretical Comp-Sci while simultaneously learning Perl has taken up the last few hours of my life and promises to take up a few more before I'm done.