Is there something like Geometry- and Attachment constraint??

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  08 August 2009
Is there something like Geometry- and Attachment constraint??

Coming from a MAX/Maya background I'm currently trying out different things in XSI. Now what I often use in Max is the Attachment constraint (where you can constrain an object to a polygon face, for example) and the Geometry Constraint in Maya, which basically constrains an object to the surface of another object while you are still able to move it around (practically allowing you to slide an object over the other objects geometry).

Is there something similar in Softimage?

I've found the Surface constraint in Softimage but that seems to be somewhat different ...

I'd be grateful for any advice ...

-Alex
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  08 August 2009
http://forums.cgsociety.org/showthr...p?f=24&t=788816

That's an ongoing thread with the same question.
 
  08 August 2009
Thanks Jettatore for your quick reply!

Really pretty ueseful thread indeed, but I guess I didn't make myself clear. I'm looking for constraints, meaning, that in animation, the locator (for example) would stay attached to the Base objects face, no matter how it deforms, OR in case of the Geometry constraint, you can animte the locator around and it will always stay pinned to the surface of the constraining Object!

Hope this is clearer!
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  08 August 2009
From your description of Max's Attachment constraint, it sounds similar to the Object to Cluster constraint in Softimage.

The Geometry constraint in Maya sounds closest to the Surface constraint, which unfortunately works only with NURBS not poly meshes.
 
  08 August 2009
In Softimage, sort of - kind of...

You can constrain to a "NURBS surface". I don't believe without additional plug-ins you can constrain to a polygon surface.

From the manual "Constrain Surface"

"You can constrain the displacement of an object based on the UV values of the constraining NURBS surface object or the U value of the constraining NURBS curve"

I.E. You can't just use the move tool anymore, you have to animate the U and V values of the Surface Constraint Operator.
 
  08 August 2009
Yeah, I've looked at the "Constrain Surface" and it is a promising start. It's not so bad that I can only use Nurbs surfaces, I just wish I could still freely move the object around. I often used that to constrain controls on a surface ...

Are there any known plugins that can do the tick, any of you know of?

Thanks a million,

Alex
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  08 August 2009
If you want to do it without plugins, you can fudge one by making a 1pt curve. make a null using object to Cluster to the curve. Shrinkwrap the curve to the source geometry (use nearest surface).
Now you can move the curve around and it sticks to the nearest surface of the mesh Hence the null does too.
That wont give you tangency and normal direction but theres bound to be an easy fudge for that too.
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Over one hundred polygons
 
  08 August 2009
Oh, pretty nifty trick Pooby.Good stuff.
Appreciated!

cheers!
 
  08 August 2009
Ah nice Pooby! I'll go and try that out right today!

Awesome
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  08 August 2009
Thanks for the help guys!

While working on this stuff I found an even simpler way (at least for
what I want to do) ...
Simply create a ribbon (I used a poly, haven't tried with NURBS yet,
define each surface Quad to a Cluster and use the Object to Cluster
constraint with Tangency and Normal settings on!

This will have your joint follow the orientation of the ribbon segment
nicely!


Now what I still need to find is a way to basically do it the other way
around, having an object stick to the surface of another Object, but
still be able to pick and move it around on that surface - the whole
surface of the Object, which didn't work with the object to cluster
plugin ...

I'll try around some more!!

-Alex
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  09 September 2009
Sorry for resurrecting a stale thread, but I think I was able to code up a scripted operator that constraints an object to the surface of a polygonal mesh.

Watch the demo here: http://vimeo.com/6819594/

Info page: http://shaderop.com/softimage/geometry-constraint/

Direct download: http://cid-485226d6dd07a5e2.skydriv...nstraint.js.zip

Hope someone will find it useful
 
  09 September 2009
@ShaderOp

Works perfectly. Thank you very much
 
  09 September 2009
shaderop - looks great thanks for sharing! Plus your shape tools look awesome and should be a real production time saver.

cheers!
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www.matinai.com
 
  09 September 2009
Originally Posted by ShaderOp: Sorry for resurrecting a stale thread, but I think I was able to code up a scripted operator that constraints an object to the surface of a polygonal mesh.

Watch the demo here: http://vimeo.com/6819594/

Info page: http://shaderop.com/softimage/geometry-constraint/

Direct download: http://cid-485226d6dd07a5e2.skydriv...nstraint.js.zip

Hope someone will find it useful


Awesome! Thanks so much.
 
  09 September 2009
My pleasure

Programming it was a lot of fun actually, albeit in an odd, masochistic sort of way.
 
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