Hello all,

I couldn't find any help with this in the docs or on the forum. I just finished the animation chapter in Will Cunningham's out of date “The Magic of Houdini” and ran into some issues with the CHOP driven animation of a dragonfly (see attached).
I'm not sure if the issue is due to an error on my part or b/c the .hip file included with the book is out dated. The goal is to add together the twist and goal tx with the body tx using a math CHOP node and apply a lag to these curves before exporting, but if the book is followed it only applies the export to half the data.

My question is specific to the syntax of the node parameter in both the fetch1 and export1 CHOP nodes. The book instructs:

“/obj/*twist? *goal?”

to be entered for both the export and fetch nodes, but it seems like the export node only exports half the data (the one right after /obj/). I entered:

“/obj/*twist? /obj/*goal?”

into the export node, and that appears to export everything if I middle-click, but I'm not sure that is correct, and the same expression/pattern throws an error if I put it in the fetch node.

OK, I just noticed another issue and will include it in this post, since it is related. I used a mirror operation to create the bone geometry for the right side of the dragonfly and now the goal and twist nodes on the right side have a reversed X direction (apologies for the incorrect terminology =\), meaning that -x is now +x, so the CHOP override causes the goal geometry to travel in the opposite direction (interestingly, it doesn't seem to affect the twist locators…). Did I do something wrong or is this the intended result after a mirror?

Sorry for the long post, trying to wrap my head around things and using this old book there are a lot of error prone variables due to version mismatches… thanks for any help that folks can provide!