A common thing to do in 3D workflows is to make an object invisible to the render engine. Either completely invisible or invisible but still cast shadows and reflections. In geek parlance, no primary rays but secondary rays. If you are a Cinema 4D user, you can achieve this through the
Seen by Camera option in a
Compositing Tag. Houdini users are accustomed to the
Phantom option. At least this is how I came to learn it by. So how to we disable primary rays in Houdini?
In early versions of Houdini, you could disable primary rays by checking on the
Phantom switch. Simple enough. Just good old fashioned one-click wonder.
This option is accessed differently now. I didn’t notice in what version this changed but as of Houdini 15.5, the
Phantom switch is no longer there. If you go to the object’s Render tab, you will find something different. This is now know as
Render Visibility. Which makes sense. It also includes a dropdown menu with several other options. In here, you will find the
Invisible to primary rays or
Phantom option. We are back in business!