On the attribute wrangle sop there is a little button next to the snippet window that gives the help tip “creates spare parameters for each unique call of ch()”

There is also a little drop down menu beside that.

It looks like there are some presents built into the wrangle node that you can select from that drop down menu… but I'd like to know more info about this menu. Is it possible to save our own vex snippets in this list? How does this differ from using presents like with what's build into l-systems?

As for the “creates spare parameters for each unique call of ch()” button…. what does this do? I attempted to put f@foo = set(ch(“test”)); and then clicked it and was able to create a float parameter, the same with when I tried with a string. But I'm not sure on how to create a vector spare parameter doing this. Is it possible?

that list is populated from VEXpressions.txt in your houdini dir, possibly as well from home dir prefs
difference from preset is that it changes just snippet code, not the whole layout and parm values, so it's quite handy when using in POP nodes (however not so user friendly as you need to exit that text file to add more and the dropdown always replaces the code)


as for the button to create parms, you need to use specific ch?() functions to hint the type, which you should be using anyway
ch() and chf() creates float parameter
chv() creates vector parameter
chi() integer
chramp() ramp
chs() string
ch4() matrix
.
.
.

Ah, thanks!

I'm used to using hscript expressions, but never really dove into vex. Was accustomed to ch() and chs() but no other variations on it.

http://www.sidefx.com/docs/houdini15.0/vex/functions/ [sidefx.com] is going to be my new best friend.