I am trying to make a simple “instance along curve” kind of HDA for Maya 2016 Houdini Engine and it seems that I cannot get the NURBs curve in.

I create a NURBs cuve in Maya, plug it in the HDA, create a polygon box and plug that into the HDA and nothing shows up. When I send the scene to Houdini for debugging, there are no points on the curve that I plugged in.

Can someone please test this? It feels an awful lot like a bug in Maya 2016 to me. Or maybe I fail at creating the right type of NUBRS curve? Or maybe I plug stuff into the wrong inputs.

Yup, I was able to reproduce this. It's definitely a bug. I'm still looking into fixing this.

Thank you for looking into it! Is there a rough ETA for a fix?

It shouldn't be too difficult to fix. Maybe in the next day or two.

Thanks!

I just made a fix for the input curve issue. The fix should be in tomorrow's 15.0 build (15.0.311). This should get input curves working again.

After that, I also had to make a small change in your asset to make instancer work. In your original asset, the instance node is directly referencing the path that's given to the asset's path parameters. This would be the right thing to do in Houdini, but unfortunately, this doesn't work with the Maya plug-in. At the moment, the output instancer can only instance objects that also exist in the asset. this means you actually need to object-merge the input geometry into your asset as a separate object node. See the attached asset to see what I mean.

Thank you!

Small follow-up:
Things work in Maya now, but in Houdini the procedure is broken due to an infinite recursion error.

I could work around it with a simple switch, but I wonder whether that is expected behavior, or whether there is a solution that works in both Houdini Engine Maya and Houdini.

On the topic of a simple switch it also made me think of: https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=41858&sid=8d67e4ef371e5eda9f0fff575a5d8d07 [sidefx.com]
And whether anything happened on the topic.

Ah, I see it. Since I already added a switch to use a default geometry inside curve_object1 and box_object1, there's no need for the path parameters to have a default. This is why there's an infinite recursion. Simply remove the default values for the curveObj2 and instanceObj2 parameters, and the asset will work again in Houdini.

Thanks, brilliant!

There's another thing to watch for. There's a known issue in Maya with saving ramps parameters. If the first key is zero-position and zero-value, Maya will think it's a default value, and not save the value into the Maya scene file. This means the next time the scene file is loaded, the first key will be missing. The workaround at the moment is to set a really small (e.g. 0.001) value on either the position or the value. Maya will then save the key to the scene file.

Thank you!
- IMHO, all users should be able to see the list of all known issues/bugs.