1, the whole graph is invariant (1 graph is a cyclic class. 2 Figure is a square class);

2. Small graphics are transferred from the inside out;

3. The position where the small figure appears must be a plane (you can see it when the big circle in 1 figure becomes a semicircle).

So in Figure 3, it must be:

1, which must be a cyclic class diagram;

2, small graphics must be transferred to the outside;

3. Small graphics must appear on the plane of large graphics.

As for the contact surface, it can be plane to plane, or the arc of a small semicircle faces the plane of a large semicircle.