I'm currently doing an animation on an automatic transmission for a client and it took me some time to figure out how to "fake" render booleans in Octane. As it took me hours and hours (even if it's now quite simple), here is how I did it.
Scene: https://www.dropbox.com/s/womlu91uwcoqv ... oolean.mp4
1. Create a Mix material node.
2. Use the "Polygonal side" node to create a material for the inner and a material for the outer shell of the model.
3. Create different materials. In my case, I created a "Glossy" material node for the outer shell and a "Diffuse" material node for the inner shell.
4. Create a "Transmission filter" pass in Octane. You will see that only the diffuse material will show up in the "Transmission filter." It should be black.
5. Create the "Beauty" as well as the "Transmission filter" passes and use the "Transmission filter" pass as an Alpha channel (e.g. in AE). That way, you can use whatever color you like for the "hole filling."
This, of course, is a work around. You don't see any reflections or shadows, and it can also be a little bit tricky when you need other diffuse material. You may then use Light passes or any other pass that will give you the possibility to separate the inner from the outer shell of the model.
Sparrowhawke3D is also creating a new plugin for Carrara that can do real cross-sections. That way, you also see reflections and shadows. Here's a quick example: https://www.dropbox.com/s/0j7c3r8v87muv ... arrara.mp4
Hopefully, Octane will come up with a render boolean any time soon
Best wishes,
Thomas
