Re: "link with" expressions in rigging - good or not?

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

exactly the workaround.. but funny how link with doesn't work on shape weights.. what a strange anomaly..

 

Adam

----- Original Message -----
From: Mikko Ronkainen <noratio@kolumbus.fi>
Date: Wednesday, September 26, 2007 1:25 am
Subject: Re: "link with" expressions in rigging - good or not?
To: XSI@Softimage.COM

> Adam,
> This may sound silly but I've tried to avoid this by having all
> mixer 
> expressions in =, so it is easy to replace the mixer if
> something happens 
> to go wrong. All shapes are forwarded to ppg's sliders and
> forward to 
> controls. I do link between ppg and control if I have to, not
> being very 
> much for a scripter. Question is does this get around this
> problem? This 
> far it seems.  I can't remember who gave me the tip long
> time ago.
>
> Mikko
>
>
> On Wed, 26 Sep 2007 00:13:56 +0300, Adam Sale
> <adamsale@shaw.ca> wrote:
>
> > hey bernard.. this is a problem I've noted and reported a few
> times 
> > since v5 I believe.
> > it sees to happen only when linking shape weights to other
> controls.. 
> > setting relative values seems to only log a single value
> change for the 
> > curve for whatever reason. The key is there, but at the wrong
> value, so 
> > I always end up going in an fixing by hand or scripted
> solution. I 
> > thought for a while it was only myself having this issue, but
> I did get 
> > support to repro the problem about a year or two ago. Can't
> remember who 
> > its was though?
> >
> > this problem doesn't happen to me on linking transforms..
> >
> > other than that one annoyance, as Brad wrote, I use them all
> the time, 
> > and I'm never left out to dry...
> >
> > Adam
> > ----- Original Message -----
> > From: Bradley Gabe <withanar@gmail.com>
> > Date: Tuesday, September 25, 2007 2:00 pm
> > Subject: Re: "link with" expressions in rigging - good or not?
> > To: XSI@Softimage.COM
> >
> >> Hi Bernard. "Link with" operations are entirely stable and
> >> reliable, and I
> >> have used them many times in many productions without incident.
> >>
> >> The thing that is potentially unstable are the local Euler
> >> results you get
> >> from a pose or orientation constraint. Constraints are applied
> >> at the global
> >> level and use quaternion math for the calculations. As the
> >> results are
> >> calculated and applied back to the local rotations, they may
> >> shift between
> >> quadrants. When you have a local rotation that relies on a
> >> consistent range
> >> of values, say between -180 and 180, this can destroy the
> >> relationship you
> >> thought you were getting, since local 360 is as good as 0 to the
> >> globalvalue. This applies to normal expressions as well as "link
> >> with" operations.
> >>
> >> The solution is, any nodes you are using for expressions or
> >> "link with" ops,
> >> make sure to set animation keyframes on the local rotation at
> >> 0,0,0. This
> >> will force the global constraints to always resolve in the
> same local
> >> quadrant, and thus you can rely on your relationships always
> >> performingproperly.
> >>
> >> FYI, I have notified Softimage about this issue many times. I
> >> have logged it
> >> as a bug and also via escalation. I don't know if it has a UDEV
> >> number or is
> >> being tracked. It may be one of those issues that's too deep
> to easily
> >> solve, and there is a known workaround, so it's low priority.
> >>
> >> -Brad
> >>
> >>
> >>
> >> On 9/25/07, Bernard Lebel <3dbernard@gmail.com> wrote:
> >> >
> >> > Hello,
> >> >
> >> > Not really a support question, but rather getting a feel people's
> >> > experience in general compared to my own.
> >> >
> >> >
> >> > We have a bunch of characters, that I have not rigged.
> >> > The modeler created some shapes.
> >> > The rigger created a cpset to control the shape weights,
> with nice
> >> > sliders.
> >> > The thing is that the relationship between the shape weights
> >> in the
> >> > mixer and the cpset parameters are not (=) expressions, but "link
> >> > with" expressions.
> >> >
> >> > Now, the problem we're continually having is that somehow the
> >> > relationship between the shape weights and the sliders
> break. It
> >> > doesn't look like it's broken (I've checked 100 times,
> every element
> >> > of the expressions is there and valid), but moving the sliders
> >> has no
> >> > effect anymore on the shape weights.
> >> >
> >> > In time I have written lengthy scripts to workaround this
> problem.>> > It's ugly but it works. However, even though it's
> no longer a
> >> > show-stopper, animators are keep reporting that they have to
> >> use my
> >> > scripts to repair the shapes. The typical case happens when the
> >> > animator exports the mixer and imports it back onto the model.
> >> >
> >> > We're not using reference models.
> >> >
> >> > Perhaps there is something wrong we did in the first place,
> I don't
> >> > know. I don't know all the details of the rig (it's extremely
> >> > elaborate). However nothing seems non-legit to me.
> >> >
> >> > Obviously, my faith in "link with" _expression_ has taken quite
> >> a toll
> >> > as a result. I could have fired this to support but we're
> not on
> >> > maintenance.
> >> >
> >> >
> >> >
> >> > So my question is this: how much use of "link with"
> >> expressions do you
> >> > make in rigging? Is my experience unique? What are the things
> >> to do
> >> > and not do when using those?
> >> >
> >> >
> >> >
> >> > Thanks!
> >> > Bernard
> >> > ---
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> >> text in body:
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> >> >
> >>
>
>
>
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