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View Full Version : Need to spin on own axis

bcicio
10-13-2010, 09:38 AM
Okay, I feel really stupid not being able to figure out how to do this simple movement, but I can't seem to make a flying saucer spin on it's own axis while it banks and rolls in flight. The saucer just starts to badly wobble around a world y-axis when it banks. I start it at 0 keyframe, move it to a final position, spin it a bunch of times, and key it in. It then spins great if I keyframe other locations around the scene, but only if I keep the saucer horizontal. As soon as I bank a turn, it wobbles. I've tried parenting to a null and spinning that to no avail.

I guess it's the same situation as animating a car tire rolling on pavement as a car takes a turn. How do you get it to spin around it's own axis? Is it a bone thing?

Thanks.

4dartist
10-13-2010, 09:53 AM
You don't need bones at all. Basically you are missing a key principle lesson in rotation orders. Play with the rotations and notice, if you rotate in Heading, (pitch and bank will follow), but if you rotate in Pitch (only bank will follow), and last if you rotate in bank, (none will follow). So the order is H, P, B. So the problem is, as you rotate in pitch and bank, the heading rotation axis isn't following (which is normal) but the result is your vehicle isn't aligned anymore causing the wobble.

The solution is easy. You just need to make the saucer a child to a null object and animate the null object for the position and flying rotations (not spin) of the saucer. Then to create the saucers spin, just rotate the actual object, not the null. This way the heading rotation will always be in line with the saucer even as you move/rotate the null object.

This will also make it easier to animate the saucer flying around because now your heading isn't tied up with the spin motion, and you can use it to help fly around, for example if you were turning and tilted back, you could just pitch up and rotating in heading as you turn.

Let me know if you run into problems with the null object, I can make a scene to show you.

bcicio
10-13-2010, 10:39 AM
Got it. Thanks!