## Re: [Algorithms] Animation and change of root

 Re: [Algorithms] Animation and change of root From: Chris Haarmeijer - 2004-11-09 19:42:08 ```Doing things with or without a root both has its pros and cons. It depend= s on the application. We're currently analyzing human motion using orientat= ion and pressure sensors. The pressure sensors are located beneath the feet a= nd the orientation sensors on each limb. We want to compute position based o= n the orientation sensors. To do this, we have to fix the foot with the mos= t pressure as the root of the system so the other one can move freely (gait cycle analysis). That's why I need to change the root of the system durin= g runtime. If you would do this without a root, how would you go about this= ? Chris ----- Original Message -----=20 From: "Jonathan Blow" To: Sent: Tuesday, November 09, 2004 7:56 PM Subject: Re: [Algorithms] Animation and change of root > Right, by disparaging the root I am saying that the hierarchy is not a > good idea. > > I have found that once we start doing things that are more interesting > than playing back animations, the hierarchy becomes vestigial and a big > hinderance. Sure, if you bend your elbow, your fingers move. But if > your hand hits a wall, it stops your elbow. Influence travels both > ways, that's what being in a physical reality is all about. > > > Gribb, Gil wrote: > > >Well if you have a heirarchy, something has to be at the root. And the concept of a heirarchy is not at all artifical. If I bend my elbow, my fingers move. But if I move my fingers, my elbow doesn't move. Quite a natural relation. > > > >-Gil > > > >-----Original Message----- > >From: gdalgorithms-list-admin@... > >[mailto:gdalgorithms-list-admin@...]On Behalf Of > >Jonathan Blow > >Sent: Tuesday, November 09, 2004 12:39 PM > >To: gdalgorithms-list@... > >Subject: Re: [Algorithms] Animation and change of root > > > > > >"The root" of a skeleton is a pretty artificial concept that has mostl= y > >outlived its usefulness. Most people still do things that way, but it= 's > >not a great idea. > > > >Dynamic re-rooting of a skeleton is pretty easy; the annoying part is > >when you have all this animation data that's stored bone-relative and > >you're like, hey, what do I do with all this stuff? The most > >straightforward thing is to evaluate that animation on a spare skeleto= n > >that has a fixed root, to get the object space transforms, then > >re-compute bone space transforms for the new hierarchy based on that. > >(If you like bone space, which a lot of people on this list seem to.) > >Anyway, that's not "fast" if you are thinking > >I-am-peephole-optimizing-my-algorithm fast, but it's O(n) with the > >number of bones, so hey, whatever. > > > >But if you have time to actively experiment on this stuff, I would > >explore doing things without a root. > > > > > > > >Chris Haarmeijer wrote: > > > > > > > >>Hi, > >> > >>For an animation system, I have to change the root of the system frequently > >> > >> > >>from the left foot to the right foot. Are there any publications available > > > > > >>on the subject of fast changing of the root of an animation hierarchy= ? > >> > >>Kind regards, > >> > >>Chris Haarmeijer > >>--- > >>Keep IT Simple Software > >>Van Alphenstraat 12 > >>7514 DD Enschede > >> > >>W: http://www.keepitsimple.nl > >>E: mailto:info@... > >>T: +31 53 4356687 > >> > >> > >> > >>------------------------------------------------------- > >>This SF.Net email is sponsored by: > >>Sybase ASE Linux Express Edition - download now for FREE > >>LinuxWorld Reader's Choice Award Winner for best database on Linux. > >>http://ads.osdn.com/?ad_id=3D5588&alloc_id=3D12065&op=3Dclick > >>_______________________________________________ > >>GDAlgorithms-list mailing list > >>GDAlgorithms-list@... > >>https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list > >>Archives: > >>http://sourceforge.net/mailarchive/forum.php?forum_id=3D6188 > >> > >> > >> > >> > >> > > > > > > > >------------------------------------------------------- > >This SF.Net email is sponsored by: > >Sybase ASE Linux Express Edition - download now for FREE > >LinuxWorld Reader's Choice Award Winner for best database on Linux. > >http://ads.osdn.com/?ad_id=3D5588&alloc_id=3D12065&op=3Dclick > >_______________________________________________ > >GDAlgorithms-list mailing list > >GDAlgorithms-list@... > >https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list > >Archives: > >http://sourceforge.net/mailarchive/forum.php?forum_id=3D6188 > > > > > >------------------------------------------------------- > >This SF.Net email is sponsored by: > >Sybase ASE Linux Express Edition - download now for FREE > >LinuxWorld Reader's Choice Award Winner for best database on Linux. > >http://ads.osdn.com/?ad_idU88&alloc_id=12065&op=CCk > >_______________________________________________ > >GDAlgorithms-list mailing list > >GDAlgorithms-list@... > >https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list > >Archives: > >http://sourceforge.net/mailarchive/forum.php?forum_ida88 > > > > > > > > > > ------------------------------------------------------- > This SF.Net email is sponsored by: > Sybase ASE Linux Express Edition - download now for FREE > LinuxWorld Reader's Choice Award Winner for best database on Linux. > http://ads.osdn.com/?ad_idU88&alloc_id=12065&op=CCk > _______________________________________________ > GDAlgorithms-list mailing list > GDAlgorithms-list@... > https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list > Archives: > http://sourceforge.net/mailarchive/forum.php?forum_ida88 ```