Create a smooth transition area between pasted surfaces.
If A and B are disjoint (not overlapping) surfaces, and you paste surface A into surface B, B has two separate regions. Triangles fill in the gap, but they are not visible. To make them visible, draw a polygon around the region you want to fill in, and add that polygon to the surface as a show boundary. The invisible triangles become visible, and the two pieces are joined. To complete the process, you may need to manually edit part of the transition area by adding points.