Object inner is black with clipping camera for cutaway view - add inner lighting? I am using cutaway view with camera clipping, and managed to show the cut area by geometry node, looks soo good, but see the image there is a cube with room inside,
it is black because no light can pass through...

you agree - it looks awful ;)

If I uncheck "Ray Visibility" of the object with Shadow or Diffuse it also doesn't look so good because shadows of the objects are missing in general.

Is there a node trick to bring light into the darkness...?

As a solution I also could add a pointlight into the geometry...
but is there anyting better ?
This is because the geometry is still there, even though it's not visible to the camera. Rays bouncing through the scene will still interact with such geometry.

Instead try something like in my answer here.