MPxConstraint (or lack of) 2003-11-27 - By deane@(protected)
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On Fri, Nov 28, 2003 at 12:34:55AM +0100, Olivier Renouard wrote:
>
> > The geometry constraint achieves this amazing feat by connecting to a
> > special attribute on shape nodes called 'geometry', which is explicitly
> > intended for geometry constraints.
>
> True, bad exemple, let's say I want to replicate the "soft connection"
> behavior they have aquired in Maya 5.0 (didn't do much with Maya 5.0 API
> yet, so there might be more ways to achieve things like this that weren't
> available in Maya 4.5), by that I mean, constrained objects can still be
> moved in the 3D view (couldn't in 4.5, very few connection displayed this
> behavior in 4.5, like attribute blenders and animation curve). I remember
> a discussion on this list about the fact it was impossible to define /
> get attributes to show this sort of behavior ("soft connection" instead
> of default "hard connection") in Maya 4.5.
Yeah. Internally they're referred to as "passive" connections and they are
not currently exposed in the API or in MEL. I'm not sure why not. I
started to look into it once while on contract to Alias, but ran out of
time. From what I did see it didn't look that difficult to do, though
there could be complications buried deeper in Maya's engine. It could also
be that not enough people have asked for it to make it a priority, so make
your voice heard. :-)
So far as I know, animation curve nodes are still the only ones which use
passive connections. All others, such as the geometry constraint and skin
cluster nodes, do it through additional attributes which use normal
"active" connections. Unfortunately that's not of much use when driving
attributes on existing Maya nodes.
> Yes, actually if I want to write a "distance constraint" (object must
> stay at fixed distance from a given point") I could use the geometry
> constraint by passing a sphere as geometry.
My example was showing how to have a constraint maintain a fixed distance
above a surface, not above the center of the surface. So as you move the
surface's cvs around, the constrained object would move with them to always
remain that distance above the surface.
===========================================================================
- deane Gooroos Software: Plugging you into Maya
Visit http://www.gooroos.com for more information
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