In this network, from the mantra1 node I can render the “box” object but not the “sphere”.

It looks to me like objects can't be rendered when they're not directly in the OBJ context? I'm trying to wrapp a bake procedure in a Engine tool, how am I to do this if I can't point at OBJ networks?

You just need to specify the correct path to the Candidate Objects on the Mantra node. By default it is a * which means top level.
Try setting it to subnet/* to render only what is in the subnet.

This doesn't work. I even use the op picker gui to make sure I get the correct path (which in this case is “subnet/ropnet1/objnet1/sphere”).

Interesting detail, if I assign the box and render in the IPR I get rerenders when editing the box geo. When doing the same with the sphere I don't. So it's not just that I get a blank render, the geometry isn't included in the render at all.

It works for me. Just pick the subnet, not the sphere. Type subnet/*

Try putting a light in your subnet as well (that is what I did in my test, oh yeah I also added a camera to the subnet and looked through the camera). Maybe it is working but you are just not seeing anything?

Now we're getting somewhere! Adding a camera to the objnet and using “subnet/ropnet1/objnet1/*” as candidates and “/obj/subnet/ropnet1/objnet1/cam1” for camera works.

Either setting candidate specifically to “subnet/ropnet1/objnet1/sphere” or camera to “/obj/cam1” will break the setup again. So the camera needs to be seen by the renderer somehow. I'll go submit this as a bug.

Thanks a lot for the help Enivob.