CGTalk - keeping bones together

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Zoogie

12-17-2003, 06:03 PM

Is it possible to keep bone chains from pulling apart in messiah, and stretching the mesh. ie if you pull the hand further from the body than the length of the arm, it stretches the arm. What I want to do is to be able to pull the hand without worrying that there will be gaps in the bones and hence the length of the arm is always the same.
Is am not sure how to do this. I am thinking you may need to write an expression to keep the base of each bone at the end of its parent (ie the length of the parent. But I am sure there is an easier way.

Can any one help?

maks

12-17-2003, 07:35 PM

Yep there is - muscle bones :)

M.

chikega

12-17-2003, 10:43 PM

You can take a look at some examples of muscle bones in the sample scenes - also Joe Cosman's tutorial CD's show some nice real world examples:)

Zoogie

12-18-2003, 12:05 AM

Thanks folks.
I had seen the name "muscle bones", but didnt know thats what they were for. I havent gone very far into messiah. I just noticed that chapter 13 of Joes CD has muscle bones.I am on chapter 4 :) , but its coming along.
Thanks again.

Bill_nuts

12-21-2003, 09:35 PM

Zoogie, did you get your question answered? I understand that you DONT want your arms or legs to stretch.
In Joe's rig, he has the hand bones parented to the IK goal null for the arm. This makes the hand bones move with the goal which in turn stretches the arm.
You can parent the hand bones to the forearm bone and the goal is not part of the hand hierarchy so its free to move around and doesn't stretch anything, only straightens the arm bones.
I use another null parented to the forearm bone which becomes the end effector.

All the best.

Bill.

Zoogie

12-22-2003, 01:50 AM

Thanks Bill,
You described my problem exactly.
I didnt really find a solution to my problem.
I am gonna try your method.

I tried Joes final rig and realized that the arms do stretch, so do the legs. So it seems you have to eyeball the position of say the foot so there is no stretching.

I am new to rigging, but for instance in Cinema4D, there is a switch(check box) called force position. when checked, the bones do not pull apart.

I also tried muscle bones The bones were stretching. I have still to play with that some more.

I also want to try a simpler, equally functional, rig tutorial, so I can really understand whats going on before tackling Joes rig.
Do you have any suggestions?
Thanks again for your help.

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