This is both the problem and the magic of SketchUp The fact that it devolves everything into lines (edges) and planes (faces) gives it the ability to easily compute the intersections involved as well as easily passing the triangles to the video engine.
Towards the end of this post I make that clearer (I think):
The fact that it devolves everything into lines (edges) and planes (faces) gives it the ability to easily compute the intersections involved as well as easily passing the triangles to the video engine.