I am new at Houdini but I am betting once you read my nifty and straightforward description you'll be able to point me in the right direction.

Essentially I have created a tower of duplicated NURBS Circles. That works fine. What I want to do now though is to have this other geometry SOP, let's pretend its a sphere, and I want to duplicate that Sphere and have it driven by the duplication of the circles. I can easily link the $CN variable so that when I increase the duplication of the Circles the Spheres duplicate and transform in Y along with it.

However, how can I create an expression or relationship so that if I individually do an edit on an arbitrary NURBS Circle in the group the same numbered sphere will translate with it? Is there a way to express a parenting of the Circle over the Spheres?

Example, I do an edit and then select the 5th duplicated NURBS Circle and translate it in X. I want the 5th duplicated Sphere to translate with it.

Hope this makes sense

you could use a circle primitive, copy 5 times, translate
a circle then use them as a template for copying
your nurbs circle and (in a separate thread) spheres
before merging both.

-cpb

See my post on the OdForce forum:
http://odforce.net/forum/index.php [odforce.net] act=ST&f=15&t=956&s=fa2c5e32e4dfb361d6cb07dfe2e0e554


-jeff

jeff, thanks for the advice, I posted a response over at that thread.

Sorry to confuse this thread but having two Houdini forums messed me up, I wasn't sure where to post stuff.

I just wanted to add that the suggestion made by cpb over at the sidefx forum did work, which of the 3 techniques do you think is best? I am a neophyte at this so I am trying to understand why one way is preferred over the other.

Also, I just wanted to add one other spin on this that I forgot to mention in the original thread. Once I have gotten the spheres to increase and translate as I do the same with the circles, I want to have the spheres tranlsated a little outwards from the center and then progressively rotate around the stack of circles, sort of like a staircase. I couldn't figure out a way to do that with cbp's technique, I must be missing something.

You can post to both forums. Many of us troll through both forums looking for new posts.

I seem to troll the forums once or twice a day during weekdays.

As for your question regarding related scales, there are other ways to build data in houdini that can accomplish the same thing. Sometimes the traditional approach can be much improved using a procedural approach that isn't so obvious. Let us know what you want to do and then different approaches can be explored.

-jeff

spiraling the circles is doable
with copy but seems a bit messy:

circle: set to poly,
delete: all but point 0,
copy1: set number, Y trans and rotate,
copy2: use previous as template for spheres,
convert: circle form poly to circle
referenced copy of copy1: use previous as the input,
copy3: use previous as a template for your nurbs circles.
merge: copied spheres and previous.

with this the parameters in circle and copy1 will
affect the positions of everything.

now, chuck in a spring sop after circle and add
turbulence… oookay nevermind.

-cpb

Jeff and cpb, I am still having trouble tying this all together.

I just wanted to clarify what it is I am trying to do here, hopefully you'll be kind enough to try one more time to explain this.

I am not interested in scaling at all, just dupe/copy and translation. I am basically trying to create a poll using a skin on a bunch of NURBS Circles. At the same time I want to have an equal number of NURBS Spheres (or whatever really) that are spiralling up and around the poll.

Additionally, I want to create a binding so that when one of the profile circles is translated, both the skin is affected as well as the appropriate NURBS Sphere, i.e., if I translate the 4th duplicated profile circle, the skin should change as well as 4th duped NURBS Sphere.

Make sense right?

I can currently do this no problem using the 2nd technique that Jeff described (driving the primitives with the attribute) but the problem is the Skin, once Jeff's nodes use the primitive I can't seem to use the Skin anymore. If I put the Skin in before hand then it doesn't get effected by the translation of the profile Circles.

With cpb's solution I am able to get the skinning and the “bound” translation to work, however I cannot for the life of me get the NURBS Spheres to rotate in a spiral fashion up and around the skinned poll.

So I feel like I'm almost there with both of those techniques but each is missing that final part. Maybe I don't know enough SOPs yet to figure it out, surely there's a way to get a skinning done even after a primitive node in the network. And likewise there must be a way in cpb's technique to get the proper spiral rotation.

I can't figure it out however. Btw, I agree that the first hack solution that Jeff provided is not the best way so I haven't been experimenting with it.

Anyway, hopefully I haven't annoyed everyone with this one, I'm sure its obvious to the pros here.

the previous option I posted does exactly
what you're after.
Reading it now I forgot to mention that
the delete sop is to delete all but one
point of the (poly) circle so when you copy
it with Y rotation you get a spiral of points,
which you may use as a template for copying
the spheres.
(You may also want to switch on display
points for the viewport so you can see them)
converting the poly circle to a circle primitive in
a separate thread and feeding that into a reference copy
of the first copy sop will result in a linear pile of circles
which may serve as a template for copying the original
poly circle before skinning.
Using a reference copy means you can control the copying
of both the spheres and the circles at the same time.
the rest is just merging.

-cpb

p.s. this forum could really do with a means of submitting
attachments!

cpb,

you know i didn't really pay enough attention to your 2nd post so I went back and am trying to follow that.. i get a little lost with step #6, “referenced copy of copy1..”. i'm not sure what a referenced copy means and i'm not sure where i'm putting this in the network, after the convert?

UPDATE: Ok, maybe by referenced copy you mean a copy and paste as reference on the pertinent channels of Copy1? i.e., the ty, ry and $NCY? That seems to do what I think you meant…

UPDATE #2: I think I almost have it but I must have something wrong because when I do an edit after copy1 one of the spiralled points, the skin doesn't change, here's an image of what I have at this point…



i'll keep playing with it, i am though really blown away about how the delete op (all but that one point) changes the entire meaning of the template. the whole template thang is just impressive, i don't remember seeing anything like this in XSI.

btw, if you want you can post the hip file over at odforce under a duplicate thread (see link above from Jeff) or email it to me at sharpiedeck AT hotmail.com

okay there's a hipfile posted at odforce:

http://odforce.net/forum/index.php?act=ST&f=15&t=956&s=286ad2ea42c5e7408a06b955710d36cb [odforce.net]

-cpb

Thank you very much, besides solving my problem I have a learned a lot from your file. I am new at this so these concepts seem really unreal at times and it never occurred to me I could do things the way you did them.

Much thanks again, this will go a long way in helping me understand Houdini in the future!