CGTalk - Deforming Joints "Ball and Socket"

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DrM

12-14-2001, 03:05 AM

The ball joints connected to the chest and torso are one of the
hardest of parts to deform in the body with a solid mesh.....aside from the
face...and the hands...and the....well any ways......
back to the limbs connected to the chest or torso....

One of the THINGS is that a weight map that is made to
deform when the limb rotate forward and backward may not deform
properly when the limb is rotated up and down. The idea that I'm
proposing is just that ....an "IDEA" and could be a big ass setup
but I'm just testing the waters.

For every joint you would use three bones ....one bone for each rotation.

Lets say we are working on the shoulder. The the bank bones pivot is in
the middle of the arm. Because if you twist"or Bank" YOUR arm you will see
that it dose not deform in the joint but half way down the your arm as the
skin twist's around YOUR bones.
Splitting up the heading and pitch into two separate bone is the
point that you can assigned to two different weight maps to the motion of the
arm. That is.... one for the front and back of the shoulder to be moved by the
heading bone. The second one for the top of the shoulder and the pit of the arm
to be moved by the pitch bone.

If i get this idea working and if people are interested to see
this developed..I may write and post some thing up on LWHUB
on this idea and how to maybe take it to the next level.

Here or some pix to help explain it ..

Bone ROTATION setup
http://www.newtek.com/discus/messages/2/13875.jpg
Bone WEIGHTMAP setup
http://www.newtek.com/discus/messages/2/13876.jpg

Thanks for you time to look at my idea
and any feedback would be great

Dylan drm3d@hotmail.com

Rabid pitbull

12-14-2001, 01:24 PM

I think i have seen it written before to use 2 bones like this, but in the forearm... I never really understood how the hierarchy would look. How would you parent these bones??

Sounds like a good idera, but I am still confused on how it would work. Please keep us informed on your progress.

Chewey

12-14-2001, 02:04 PM

I think your idea for 2 bones in the bicep is a bit odd. Maybe fine for the forearm as Rabid mentioned.

It appears that your shoulder geometry is a part of the problem you're having when it comes to the deformations. Check out the spiraloid site and look at the way that Bay dude creates his shoulder geometry.

I've gotten away from having use weight maps in LW7b by making sure that geometry is properly created and making sure the fall-off is properly set.

A good video to check out is the the Brian Freisinger CA Basics if you haven't done so already.

Here's a link to Rowsby's site that shows a little info on how he goes about setting up Lightwave
bones for production. He also has some interesting Sasquatch furred creations. Rowsby knows his stuff and has worked for Foundation Imaging where they use Lightwave producing tv shows.

http://www.rowsby.com/SPN_Bone1_layers.html

Chewey

12-14-2001, 05:55 PM

btw, Maybe you can try compressing those jpegs so the folks out there with old dial up modem connections have a chance to view the your screen grabs faster.

I was able to take one of your jpegs that was 470k(about half a meg) and reduce it down to 40k in Photoshop 6. Quite a savings(approx, 90% reduction) and not enough loss of detail to make a noticeable difference.

Usually I wouldn't bring it up but I have a fast cable hookup and the shots were loading pretty slow even with the cable hookup.

"I am Chewey, hear me roar!"

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