This helps to visualize the inner structure of a model.

Example

This will require interactions with the stencil buffer

Some references:

https://discourse.threejs.org/t/capping-clipped-planes-using-stencil-on-a-buffergeometry/18407/9
http://daign.github.io/clipping-with-caps/
https://core.ac.uk/download/pdf/295554133.pdf