RE: rigging dilemma: driving a parent with attributes of the child

Date : Wed, 1 Mar 2006 07:48:45 -0000
To : <XSI(at)Softimage.COM>
From : "kim aldis" <kim(at)cg-soup.com>
Subject : RE: rigging dilemma: driving a parent with attributes of the child
I'm not sure there is an evaluation order. My understanding of local and
global is that they're both just different representations of the same
thing. In fact, if you think about it and look at the values, they couldn't
be applied one after the other. Concatenating these two matrices would give
you the wrong results. 

> -----Original Message-----
> From: owner-xsi(at)Softimage.COM 
> [mailto:owner-xsi(at)Softimage.COM] On Behalf Of brad
> Sent: 01-March-2006 03:19
> To: XSI(at)Softimage.COM
> Subject: RE: rigging dilemma: driving a parent with 
> attributes of the child
> 
> I believe the evaluation order can be ascertained by looking 
> at the node stack, same as with modeling and deformation ops. 
> Start at the bottom of the kinematic stack and work your way 
> up. Since the Global node is higher than the Local, anything 
> applied to Global, such as a constraint happens after 
> whatever effect is applied to the Local transform.
> 
> 
> >  -------Original Message-------
> >  From: brad friedman <xsibrad(at)fie.us>
> >  Subject: RE: rigging dilemma: driving a parent with 
> attributes of the 
> > child
> >  Sent: 01 Mar '06 03:12
> >  
> >  There's the added complexity of the local transform vs the global  
> > transform.  Constraints apply to the global, not the local.  But a 
> > child's  local transform is not affected by the parent's 
> translation.  
> > An adjustment  to a global seems to trigger a change to the 
> local and 
> > visa-versa.  This is  a scenario you don't find in maya as there is 
> > but one transform.  I'm  actually a bit currious as to the 
> evaluation 
> > order of the local and global  transform in different 
> scenarios like this one.
> >  
> >  -brad
> >  
> >  _ANDRE DEANGELIS <ANDRE.DEANGELIS(at)UBISOFT.COM>_ wrote: Yes 
> I relise  
> > that Kim,
> >  
> >  But having tried it and seeing hat it works (at least in a simple 
> > test),  I am wondering what makes this colution less than desirable.
> >  
> >  Andre
> >  
> >  -----Original Message-----
> >  From: owner-xsi(at)Softi!  mage.COM  
> [mailto:owner-xsi(at)Softimage.COM] On  
> > Behalf  Of kim aldis
> >  Sent: Tuesday, February 28, 2006 2:29 PM
> >  To: XSI(at)Softimage.COM
> >  Subject: RE: rigging dilemma: driving a parent with 
> attributes of the  
> > child
> >  
> >  Because the rotation of the parent is driven by the child, 
> but the  
> > rotation of the parent affects the position of the child, 
> which then  
> > affects the direction of the parent, which affects the 
> rotation of the  
> > child .....
> >  
> >  > -----Original Message-----
> >  > From: owner-xsi(at)Softimage.COM
> >  > [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Andre DeAngelis  > 
> > Sent: 28-February-2006 19:04  > To: XSI(at)Softimage.COM  > 
> Subject: RE: 
> > rigging dilemma: driving a parent with attributes of the  > 
> child  >  
> > > There is only one parameter dependency here.
> >  >
> >  > If you parent one null to another and then apply a direction  > 
> > constraint to the parent (to point to the child) it workd 
> just dandy.
> >  >
> >  >!  ; In  fact, you can continur to rotate the parent in 
> branch mode, 
> > to
> >  
> >  > offset the whole set-up.
> >  >
> >  > Am I missing something here?
> >  >
> >  > -----Original Message-----
> >  > From: owner-xsi(at)Softimage.COM
> >  > [mailto:owner-xsi(at)Softimage.COM] On Behalf Of kim aldis  > Sent: 
> > Tuesday, February 28, 2006 1:48 PM  > To: XSI(at)Softimage.COM  > 
> > Subject: RE: rigging dilemma: driving a parent with 
> attributes of the  
> > > child  >  > I'd be intrigued to see how, as rob says, the 
> child is 
> > dependant  upon  > the parent which is dependant upon the 
> child, which 
> > is dependant upon  > the parent which is dependant upon the child 
> > which ...... And the  > whole thing rapidly crawls up it's 
> own arse. 
> > Whichever software you  > use.
> >  > Would have been the same in SI3D too.
> >  >
> >  > > -----Original Message-----
> >  > > From: owner-xsi(at)Softimage.COM
> >  > > [mailto:owner-xsi(at)Softimage.COM] On Beh!  alf Of  
> David Gallagher  
> > > > Sent: 28-February-2006 18:39  > > To: XSI(at)Softimage.COM  > > 
> > Subject: Re: rigging dilemma: driving a parent with  > 
> attributes of 
> > the  > > child  > >  > >  > > Maya has its benefits. It 
> handles this 
> > situation better  > unfortunately.
> >  > >
> >  > > > I don't see how you can avoid a cycle.
> >  > > >
> >  > > > As soon as you tranlsate the child in negative Y the 
>  > parent 
> > rotates  > > > causing the child to move causing the parent 
> to rotate  
> > > causing the  > > > child to move...
> >  > > >
> >  > > > _rob
> >  > >
> >  > >
> >  > >
> >  > > --
> >  > > David Gallagher
> >  > > Animator, Blue Sky Studios
> >  > >
> >  > > ---
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