So, let's look at how that happens. The user may create this sketch here. Having done that the system may return this. Then the user may decide this is not right, there is something missing here, the user may indicate that missing thing by a drawing inclusion loop and that would give the system return the set starting. The user might realise that there is something of the same stuff come in, the user might see something that is extraneous, so the system will cut that out. The strokes, the include and exclude strokes, help the user refine the sketch, the initial selection.

---