Draw, Project, and Intersect

Use this mode to quickly split fragments.

Overview

1. press shift+T to activate the mode
2. draw a 2D shape using space+left drag
3. finish (and leave mode) by flood-filling with shift+left click

Details

You can think of this mode as a flood-fill with the currently selected ID, but the flood also stops at the boundary of the shape you drew. For that, the shape is extended in 3D infinitely, along the current viewing orientation.

Since the flood-fill is performed in 3D, you might get unexpected results when the object you are trying to split is connected outside the current region you are working on.