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JHN
12-16-2009, 08:09 PM
I have once read on a blog a few lines of code in a rotation script controller that will do a proper shoulder extraction, keeping the upperarm twist bone in the right rotation. I can't remember on which blog it was, and I have searched the web and my archives a lot last week. So if anyone knows what I'm meaning, it was a ingenious piece of script that I think did make use of some clever dot acos stuff and the rotation of the upperarm was flawless...

Any help is greatly appreciated!

-Johan

Polimeno
12-16-2009, 08:42 PM
guess it was phoelix tutorial (http://joleanes.com/tutorials/flippingless/flippingless_01.html).... isnīt it ?

hope it helps.

**** EDIT ****

Arenīt you talking about this Algorithm (http://en.wikipedia.org/wiki/Dual_quaternion) ??

source 01 (http://isg.cs.tcd.ie/projects/DualQuaternions/)
source 02 (http://mayadqskinning.sourceforge.net/)
source 03 (http://portal.acm.org/citation.cfm?id=1230107)
source 04 (http://74.125.47.132/search?q=cache:NfP3_LaNxxsJ:www.cgg.cvut.cz/members/kavanl1/papers/sdq-i3d07.pdf+duo+quatarnion+skining&cd=2&hl=en&ct=clnk&client=firefox-a)
source 05 (http://softimage.wiki.softimage.com/index.php/Dual_Quaternion_Deformation)

JHN
12-16-2009, 09:46 PM
Aawh excellent!!! It was that tutorial indeed!
I didn't mean dual quaternions, but I wouldn't mind having it in max ;)

But thanks a lot for this, been searching for some time for that one!
-Johan

eek
12-16-2009, 10:19 PM
guess it was phoelix tutorial (http://joleanes.com/tutorials/flippingless/flippingless_01.html).... isnīt it ?

hope it helps.

**** EDIT ****

Arenīt you talking about this Algorithm (http://en.wikipedia.org/wiki/Dual_quaternion) ??

source 01 (http://isg.cs.tcd.ie/projects/DualQuaternions/)
source 02 (http://mayadqskinning.sourceforge.net/)
source 03 (http://portal.acm.org/citation.cfm?id=1230107)
source 04 (http://74.125.47.132/search?q=cache:NfP3_LaNxxsJ:www.cgg.cvut.cz/members/kavanl1/papers/sdq-i3d07.pdf+duo+quatarnion+skining&cd=2&hl=en&ct=clnk&client=firefox-a)
source 05 (http://softimage.wiki.softimage.com/index.php/Dual_Quaternion_Deformation)

This is essentially the math i use for all deformation systems im working with -it handles natural twist/deformation extremely well. Ive formulated a theory that they are a core component to natural motion/rotation.

The core idea can be used anyway from the spine, shoulder, wrist, elbow etc and in a variety of ways.

I'll post some of my findings soon on my blog.

Polimeno
12-16-2009, 10:28 PM
I'll post some of my findings soon on my blog.


hey Charles,
sounds pretty interesting !!
Would be awesome if you share your thoughts with us, although iīd love to hear more framework ideas about that.


seeya

eek
12-17-2009, 12:43 AM
Well basically I've been studying indirectly biotensgrity - which is basically biological tensional integrity. The basic though behind it is that there are core systems in place to stop you basically breaking - i.e tensional integrity to keep us together. Theres a massive body of work on the subject known as 'Anatomy Trains' this is research into the miofasi of muscles skin etc and core tensional lines that run through the body - an ache in the shoulder for example maybe caused in the lower back.

Well anyway what i took from this is that there must be a common system that joints use regardless of DOF that keeps them in check and more importantly there surrounding deformation.

Deformation essentially is a system to keep joints from popping out of there socket - volume preservation is a natural bi-product of these systems as scale is a bi-product of a matrix.

So this added to a recent master class i went to formulated an idea that you could build a common system to not only solve twisting but also volume preservation. Which is also fits well with the general rules of rigging:

Poses to be created quickly and easily.
Deformation that aids the fidelity of the pose.

So basically come up with 'wedges' that are bound in a system similar to what pheonix described (which can also be doubled up) to describe complex joint deformation: shoulder/wrist/spine and simpler ones: knees, elbows etc.

Its really really simple - but works out really well. There some extra stuff i use for extra fidelity but that the basic notion.

JHN
12-17-2009, 12:38 PM
Dang Charles, I get the gist of it, but I'm nowhere near the level of abstract thinking needed to implement even the notion of the mechanics you describe. I mostly copy and paste code that work, and if I need it a lot, I'll dive into it some more, to really understand the thought behind stuff. But since I'm still struggling with basic trigonometry, I'm just really happy that people like yourself are sharing this info!

But then again you are a character TD for a big game company and I'm an generalist and "parttime" TA for a boutique animation shop.

If I may ask, will you post examples next to the theory, that works best for me, so I can from a sample file try to deduce what is going on, and match the theory with the practice.

Thanks!!

-Johan

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