Is there a way to get a vop parameter's value at a specified time? this would be similar to the lookup chop

i want to use this as a more controllable replacement for the spline operator in vops

If you have a channel in your parameter (and you have since your parameter is apparently animated) you can use one of expressions like: chf, cht.
See in texport: exhelp chf

sy.

thanks symek, but i'm working inside vops, so i can't use any expressions functions!

Make a Parameter VOP to house the expression (even if the parameter is marked “invisible”) and wire the value in where you need it.

thanks jason, this sounds good - i guess this is what SYmek meant as well!

now a problem with this for my specific case:

the time value for the lookup comes from a point attribute… now it doesn't seem like you can use $PT or other local variables in expressions on a vop SOP.

what i would need to do is something like

cht(“deform_curve”,point(“.”,$PT,“timeVal”,0))

to get the time attribute at each point, right? any ideas?

I'm not really sure what you're trying to do but definitely CHOPs are your friend. See rough example!

hope this help,
sy.

cool SYmek, thanks a lot!

i will try to do what i'm working on in chops, maybe it'll work. what do you think about speed of vex vs chops for manipulating geometry?

anyway maybe it would be worth an RFE having this ability inside VEX/VOPs. I'm thinking along the lines of an import attribute with a time parameter

though jason's suggestions works fine for many things, i'm sure having it all in vops would be much faster than using an expression

This is not so easy. Think for a minute what VOPS really are and when & where they are executed. Vops are just a front end to vex language. They build blocks of code. The code is send to mantra along with values taken from parameters evaluated in Houdini. Now mantra is not a time machine. It computes a state in small piece of time - your frame. Thus expressions in VOPs is not a best idea. I can't imagine for what specific purpose this could be helpful. You really can sue VopSOP as a expression machine - but again not related with time. In case of a time related issues CHOPs rock! And as to your question they are very fast! They can handle huge amount of data in a short time. Try!


cheers,
sy.

yes, i thought this might be the answer. what i really just wanted (unrelated to any specific purpose) is a better ‘curve’ interface for vops, more controllable than the spline operator.

apart from that, for what i'm actually trying to do your suggestion seems perfect!

thanks a bunch