Eneroth Cut Surface Organizer
When cuts that aren't flat are desired the model can be manually divided into groups representing each side of the cuts. This script helps putting the cut geometry on its own layer so it can be hidden when the model as a whole is shown.
Eneroth Cut Surface Organizer

When to use this extension

In most cases the native Section Cut tool works just fine. It hides parts of the model without affecting the geometry itself so cuts can be added, moved or deleted in a matter of seconds. However, the native tool can only make flat cuts which isn't desired in some complex models.

The workaround is to make each side of the cuts its own group and put these groups on their own layers so they can be displayed individually. Scenes can be used to fastly show or hide specific groups. These groups could be floors in a building for instance. This also has the advantage that the cut surfaces can be drawn as ordinary faces instead of the model looking hollow.

When the model as a whole is shown these cut surfaces (those where the groups touches) and their bounding edges should be hidden so the model doesn't look divided. This extension moves that geometry to its own cut layer in just one click. Without a script to help this is a quite tedious process, especially since you need to do it quite often when drawing close to the cuts because geometry is easily drawn on the wrong layer.

How to use it

For the extension to work it's very important that the model is drawn correctly. The groups to look for cut surfaces in MUST be drawn directly in the model root (not inside other groups or components). Since the extension only looks for groups in the model root nested groups, such as furniture, aren't checked which reduces execution time a lot.

Since the extension identifies cut surfaces by their material it's important that the materials are named correctly. Multiple materials can be used. For instance one for the building, one for the terrain, one for vegetation and one for water. These materials should all be named "!Cut!" or "!Cut#n!" where n is any integer. The expression mark makes the cut materials appear first in the alphabetically sorted material browser.

To run the script simply click its icon in the toolbar or click Plugins > Hide Cut Surfaces.

Limitations

Curved surfaces

Because of how Sketchup renders faces connected by smooth edges shading errors occur when the cut isn't perpendicular to the curved surface. This means that this cut technique should not be used on double curved surfaces (e.g. domes) but single curved surfaces works fine (e.g. the towers shown in the first picture).

Moving cuts

Moving these manually drawn cuts can be quite time-consuming since you need to move geometry between groups and remove the old cut surfaces.