The reference part intersects each of the slides that you specify. When you create this intersection, one or more intersection loops are created. You can separately handle each loop. If a loop does not intersect the existing silhouette curve, the system discards it. If the loop does intersect the silhouette curve, the system removes the portion of the silhouette curve inside the loop.

Points of intersection with the silhouette curve split the loop into upper and lower chains. These chains are added to the existing upper and lower chains of the silhouette curve and treated the same way.