how do I.....

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toonertime
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Joined: Mon Feb 26, 2007 11:34 pm
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how do I.....

Post by toonertime »

This is a simple prob I am trying to work on:

Say you want to use bones to animate a worm, or
anything tubular, like legs, arms, etc.

How do you do this without creating "kinks"
in the tube, and having a nice natural animation?

Bones seem to distort vectors very easily, and
I am wondering how you guys manage around
this?
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slowtiger
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Post by slowtiger »

Right now I have to work with a bunch of animals, including a giraffe and an elephant. So I have a neck and a trunk and some tails. Most are done with a nice chain of short bones, about 1.5 to 2 times as long as the thickness of the "pipe". The outline of that pipe has one point for each connection between two bones, and this on each side. The points are bound flexible, and that's it.

The elephant's trunk is boned differently because it needs to stretch. The bones cross each other like in this Herringbone stitch: http://en.wikipedia.org/wiki/Image:Herr ... titch2.jpg

You have to take care to set the curvature of the points correctly. Most times the default is OK.
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heyvern
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Post by heyvern »

I also use simple bone chains.

But I like to add in "extra" levels of bones for simpler control.

For instance if I have 10 bones in a chain to control a tail, to get smooth motion I would have to key frame all 10 bones every time I move the tail. This gets to be a bit tiresome.

I will add in one or even two "control" chains that the tail bones are constrained to.

Hard to explain, so below is a simple test file.
In the animation both scaling and rotation are controlled by just 3 bones. There are 10 bones in the "tentacle".

http://www.lowrestv.com/moho_stuff/forum/tentacle1.mov

http://www.lowrestv.com/moho_stuff/forum/tentacle.anme


Check the bone constraints. That is what makes it work. Each group of two bones is constrained to control bone. The second bone of those two is constrained at 0.5 to that bone in the control chain to smooth the motion.

I went a bit overboard with this just for demonstration purposes. You could probably get away with one control chain with 3 or more bones. It depends on how many bones you want to have to key at each frame to animate the tail. The key is to experiment.

In some cases you might not have enough control of the "tentacle". With some "extra" bone chains and a different set up you can control specific sections of the "tentacle" independently.

-vern
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