How would you control object positions with VEX

It has to be fast the, vex SOPs work on 100's of points and I would only want to work with 20 objects

I want to take in several object transforms and use VEX to work with the information and then send it back to other objects.

this may sound like a job for chops but from what I have seen that isn’t the case mainly because VEX for chops only works on one channel and outputs only one.

This may be a feature request but what about some kind of “VEX transform operator” that can take in several matrix values and out put to several matrix values. The “Inverse Kin CHOP” pulls of most of these tricks but if we also could make something that could do these kinds of operations but let us under the hood.

I really want to wire together rigs within VEX where I can make my own constraints.

If there is an established work please tell me. I am new to Houdini so I am full of ideas that have existing solutions.

Vex SOPs can only realistically control point positions. Not good for you. Sure you could hack in geometry to represent all your object properties, but the expressions needed to grab that geoemtry data out of a VEX SOP would kill any performance advantages gained.

You would be much better off using CHOPs as they come. The standard CHOPs offer a lot of control. If you are stuck, you can use the expression CHOP but this is a pretty hard hit in terms of performance. I am pretty sure you can do what you want with the standard CHOPs. If not, then I will be very interested to see why not. Some CHOPs are pretty clever in their implementation.

-jeff

Can you make constraints between 3 objects within chops?
Do most operations have to happen at one channel at a time in chops?
A rotation is a complex thing and to looke at it one channel at a time is counter productive.

I guess i see all the matrix, quat and vector operations in VEX and i and they are just begging me to use them.

By the way where are some examples of houdini files…. I dont have a houdini CD and i am not in the US so I dont have the example files on the second CD where are some examples of houdini files i can take a look into to lern a thing or two?

meshsmooth
Can you make constraints between 3 objects within chops?
Do most operations have to happen at one channel at a time in chops?
A rotation is a complex thing and to looke at it one channel at a time is counter productive.

You can constrain 3 objects even without CHOPs, using the Blend Object. But yes, you can do it in CHOPs, and a lot more. CHOPs can work on hundreds/thousands of channels simultaneously if needed, and they're fast.
Look at the help for the MathCHOP, for example. The ObjectCHOP would also interest you for constraints. The same goes for Transform, Pretransform, Geometry, Composite, Blend, Lookup CHOPs.
Take a little time to explore CHOPs, because they open a whole new way to approach things.

Dragos

PS and you can always use VEX/VOPs to build a CHOP if you really need some special constraints…