CGTalk - Animation question

Roger Eberhart

02-19-2003, 11:49 PM

OK.... Last month I was at a Lightwave users group meeting in LA. While some guy was talking about video editing in Toaster (yawn), the guy next to me was trying to figure out how to roll a cube across a surface.

This is actually kind of difficult in Lightwave. You can't animate the pivot like Messiah. The solution he came up with was parenting the cube to a null. He placed the null on the front bottom edge. Then he rotated the cube 90 degrees around the null. Then he moved the null to the new front edge. However, this caused the cube to move. So he had to correct that by moving the cube back. Then he rotated the cube around the new corner. Then repeat...ect. Kind of a pain.

I thought this should be a piece of cake in AM, so I played around with it at lunch. I tried making an action in muscle mode, but found that the cube would deform in odd ways as AM tried to move the points in the straightest path between poses. So muscle mode is a bust since I don't want the cube to deform. I guess I will have to do something with bones and nulls.

Anyway, how would you approach this problem in AM?

Nonproductive

02-20-2003, 03:53 AM

Maybe one of these tut's will help?
http://www.jb-av.com/tutes/rocking.html
http://www.jb-av.com/tutes/rolling.html

Roger Eberhart

02-20-2003, 04:30 AM

Thanks. Not exactly what I'm trying to accomplish, but it gave me some good ideas.

JBarrett

02-20-2003, 06:18 PM

If the cube is "rolling" in a straight line, this would be easy to do as a cycling action with stride length...provided the cube is also very flatly textured so you wouldn't notice that it's cycling back to the same side with every rotation.

I remember seeing a tute on something like this a long time ago for a different app. It involved laying out a series of nulls or bones that were setup in a specific parenting relationship, and all on the same plane as the base of the cube. One null/bone is at an edge of the cube, and rotating it turns the cube over onto one side. At that point, another edge of the cube lines up with another null/bone (which is a parent of the first). Rotate that to roll the cube over onto another side. Add enough nulls/bones to roll the cube wherever you want. The tricky part is laying out the nulls/bones in the right position so that each one matches an edge of the cube after a certain number of rolls, especially if the rolling isn't in a straight line. This technique would also allow the cube to be textured however you want it, as it would actually be rolling onto various sides.

(BTW: thanks for sharing the links to my tutes, Nonproductive!)

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