Character Technology
Character Technology
Here is a video that talks about some more advanced usage of the quaternion double-cover property, and specifically how you can use this to eliminate unwanted blending problems in your animation system.
One thing to note, is that I get a little too excited in one part when I'm doing a physical demonstration of a blending glitch, and I accidentally say "extra 720 degrees" instead of "extra 360 degrees". There is never an "extra" 720 degrees so while most of the time I say "extra 360" in the video, I do slip up once so please don't let that throw you :)
Also, Dave Moore from RAD Game Tools sent me a link to this cool web page that shows how to do the belt trick I mentioned in the lecture: http://gregegan.customer.netspace.net.au/APPLETS/21/21.html.
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I did some interesting tricks to make my b-spline solver handle multi-order discontinuities. This lets it do stuff like correctly fit the motions of things that teleport, bounce, etc., without having to break the curve up into sections (you still get one nice big b-spline, that you can evaluate normally). I wrote up some notes on how I did it.
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I wrote an extremely fast and accurate high-res to low-res mesh projection tool that I included in the exporters for Granny. It actually knew the exact worldspace quadrilateral mapping for each texel in the projecting texture maps, and would cast rays out of the resulting shape.
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I developed a technique for looping motion extraction called Periodic Loop Decomposition. While it works very well for single motions, it breaks down for transitions between motions mid-loop, and so I don't think it's quite where it needs to be to be a standard tool. But someday it might be worth looking at again.
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Quaternions for real-time animation were very poorly understood when I started working with them. The conventional wisdom of the day was that to interpolate quaternions, you had to use something expensive like SLERP, which is what I did at first. But I later discovered with some experimentation that you have many more powerful options. My initial e-mails on the subject are here, along with the original screenshots from my cute little MathVis test harness.
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