If any one has used contraints in maya…like contrain to normal, contrain to point, contrain to geometry, contrain to aim….etc…

is there something like this in houdini…? or is it something you have to build from the ground up?

Not sure what they do but are they like the rivet and sticky objects?

Step this way my good man, this is why i love the ODwiki….. For character constraints you want this page
http://www.odforce.net/wiki/index.php/Character [odforce.net] but for the sticking stuff to geometry and the like you want the rivit object and you can also roll your own. but the pages on constraints outlines most of the tools you may want to create.

but if you want specific solutions just ask.

thats a great source of information….yet Im not really interested in anything involving characters right now…mainly just learning for procedural modeling..etc

from what I read it looks like I should take a look at the transform CHOP and a couple other ones and use those….

is there anything you could think of that I should know not having to do with characters?

thanks

well you should visit this page and find out how to make the equivlent of all your maya constraints. read this page and KNOW the blend object.
http://www.odforce.net/wiki/index.php/Constraints [odforce.net]

But why worry about trying to emulate Maya constraints for procedural modelling when there are umpteen different ways to do that in SOPs that we all do day-in and day-out?

Use tools like grabbing point positions or any other attributes with the point() expression. With that, the Attribute Create SOP and some blending functions like modblend I can create many different positions in space and blend between them all. I can orient data to any fixed or dynamic co-ordinate system in so many ways: VEX and VOPs, orient() and other expressions that even handle up vectors for orientation, POPs, CHOPs, even the friggin' compositor can do procedural modelling in real funky ways.

There are the SOPs that form the stock and trade in constraining data: Align SOP, Sweep and Copy SOPs, second input in to Point SOPs, and on and on.

There is a whole world of options to procedurally build data and have any number of dynamic constraints built on whatever rules you want!

Don't limit yourself to “literal” channels. Try to free yourself from that constraint levied on you by Maya and start to use the data and the procedural tools in Houdini to build in any type of relationship you want. Place down some of the above mentioned SOPs and open the help then start parusing the example files. Many a top Houdini user has learned his/her stock and trade from the example files.

I was always mystified by the word “constraint” when I first ran in to it a few years back. I don't see the world as “constrained” but liberated! I use the term “relationship” instead of constraint because it is far more applicable to CG. Yet another Maya funky colloquialism. :x
In Houdini I build relationships between data and parameters that give me what I want, when I want it!

And yes, I am a glass-half-full kind of guy. Wolfwood, JC, Simon and other Houdini users are a glass-overflowing kind of guys! ops:

thanks a lot…yeah I'm definetly into the procedural approach…I do feel maya can be a bit unorganized…I just found it quite easy to “contrain” in maya…but you are right its more of a relationship…

I am definetly interested in orienting things…did you say there is an orient expression? or are you talking about the vop…

Open the textport and type:

exhelp -k orient

and that returns you a bunch of expressions that have orient somewhere in the help. A great place to start.
From that list, vorigin, and objlookat work with object references and allow you to grab world positions of objects in two different contexts.

Fyi, exhelp -k <search string> is very useful for searching all the expression functions for keywords and returning those functions that have the key word(s) in their help. Can also use the on-line help in Houdini.

Another class of expressions deal with points and primitive attributes, namely the point() ad prim() expressions. Try at the textport typing exhelp poi and you will get many of the point specific functions. Same for Prim.

There is an morient() expression that returns the transform matrix that is the rotations required to fold one vector on to another vector. You usually embed morient() inside an explodematrix() expression to extract the various components of the transform matrix.

I tried exhelp -k constrain in the textport and got nothing. :wink:

jeff
I tried exhelp -k constrain in the textport and got nothing. :wink:

But if you type “constraint” (in the help search, not in the textport), you get quite a bit

See?!? Houdini IS constraint-aware! :twisted:

(sorry jeff… just couldn't resist)

This thread is about Object and geometry constraints. Not DOP constraints which is essentially what you get in the help search using “constraint” as the key word. Not really one entry is returned on what this thread is about.

Now if you type “relationship” in the search, DOPs is all over the place again but at least I get some hits that are relavent to the thread:
-Match Houdini cameras
-Blend Object
-Copy, paste and link parm values
-Blend parents of objects
-Point Sop

To be fair, there should be more relavent hits to this thread than the above for both keywords. I'll have to see what can be done about that. I wonder if the search also gleans through the comments on Operator Nodes in the help card example files?