CompuServe Thread

>> Can anyone tell me why I get a camera roll when the camera passes over or near it's target. This doesn't happen in every animation. << It apparently has something to do with the way 3DS deals with the x,y,z universe. One solution I've heard offered is to create a dummy object at 0,0,0, link everything in the scene to it, and rotate it 90 degrees in any direction. You can now look "down" at your target without the flip/flop.

<Flip Flop> I haven't found a way around it. If you find an answer I'd like to know. Scott Lunsford

Hi Will, << camera flip flop.. >> Gary answered this back in June.. Here's a repost of related threads… "You can also try linking everything in your scene to a dummy rotating the dummy 90-degrees on frame 0. This will likely shift the entire animation to an orientation in which you won't ever being passing the camera over the singularity at the poles. Note that the singularity is just an artifact of quanternion mathematics, which was originally developed in the 1800's to inhibit the gimbles on big sailing ships from locking. All high-end 3D animation systems use this form of math for smooth motion, but like anything it's not perfect. Quaternion math (used by almost every animation system on the planet for things like camera and object rotations) is polar-based (using a three-component vector and an angle/scaler), which causes a singularity along the polar axis. As the vector approaches that singularity, its orientation becomes ambiguous. In order to deal with the ambiguity, the program maintains continuity of motion (or at least tries to minimize discontinuities). This math was originally developed in the early 1800's to keep the gimbles on huge sailing ships from locking as they traversed their own polar singularities. If you're interested in learning more about it, check out an article in Computer Graphics & Applications magazine (the ACM Siggraph bible) by Ken Shoemake, 1985. He pretty much pioneered the use of them in computer animation while at Xerox Parc (as far as I can remember). There is a strong relationship between quaternion math and Euler's theorem, which states something about how any displacement of an object with a fixed centroid can be represented by a single rotation about an arbitrary axis. I hope that gives you more of what you wanted, but reading over it I'm starting to doubt that's what you had in mind when you asked the question. The short answer is that it's just the way it works. – G"