The reason I'm intested in this is, that I want to build skymaps as rendered scene backgrounds within Unity. If I have a cubic environment map seen from point X with the surrounding scene, I can use the six generated textures to stitch them together seamlessly in Unity.
This provides me with a scene background which can be anything, really. A room, a distant landscape with clouds overhead, etc.
A polar panorama only works in that aspect, that I could use a large cylinder with inward facing normals surrounding my scene. If I put the panorama on this cylinder, I have a landscape, etc. This doesn't cover floor and ceiling however.
It's also a possibility, but I would prefer a cubic environment map, since I can use it for reflections in shaders and scene backgrounds in skymaps equally.
I utilized this to great effect in several realtime projects and just want to know how to get this out properly from within houdini

Well… now to the execution:
I followed the docs and your checklist, but still no cubic environment map seems to be rendered out to anywhere I can find.
A scene is provided as attachment, maybe somebody can point me to the error. When I render the scene, no cubic environment map or additional image planes are generated.