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

[Adam Sale <adamsale(at)shaw.ca>]

I get a very interesting blend when I drag and drop an objects local srt > 
posy input onto the same objects pivots > rotz input.




----- Original Message ----- 
From: "Noodles" <awalsman(at)omation.com>
To: <XSI(at)Softimage.COM>
Sent: Tuesday, February 28, 2006 8:28 PM
Subject: Re: rigging dilemma: driving a parent with attributes of the child


> No cycle.  This is how it seems to resolve in Maya:
>
> child.translatey -> parent.rotatez -> parent.worldspace ->
> child.parentmatrix
>
> and this is where the evaluation ends (the child.parentmatrix attribute 
> does
> not modify the child.translatey attribute).  It modifies the position, but
> not the actual numeric value stored in the local position attribute.  So 
> no
> cycle.  I would think it should do the
> same thing in XSI, you'd get:
>
> child.posy -> parent.rotz -> [internal parent-child propagation resolves 
> the
> worldspace position]
>
> But if I try it in XSI, it definitely does freak out and not work.  Could 
> it
> have to do with XSI's mixed transformation representation?  Or
> maybe the interface stuff that takes dragging the arrow around or typing a
> number in and decides what to do with it? (Like it's not expecting the 
> local
> space to change while it's updating...?)  Maybe in how the transforms are
> propagated from parent to child?  I don't know I'm just grasping in
> the dark.
>
> Anyway, all that being said, there's some ways you can kinda fake it.  It
> doesn't seem to mind if you set an expression from the translation of an
> object to the same object's rotation (so you can combine your translation
> and rotation), but then again, that doesn't let you rotate the child how 
> you
> want.  You can get the motion you want if you just have a sepparate custom
> parameter driving both object's position/rotation respectively, but then 
> you
> just have a slider and not something you can pull around.  Bummer.  Might 
> be
> a way to fake it with a scripted op...?
>
> -N.
>
> ----- Original Message ----- 
> From: "brad" <brad(at)cg-soup.com>
> To: <XSI(at)Softimage.COM>
> Sent: Tuesday, February 28, 2006 7:19 PM
> 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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