As shown in the figure, the cross section of the plastic sheet is a row of semicircles, and pictures are prepared to be pasted on the straight line (plane); Cut two pictures (A, B) into dozens of strips with the same width, reassemble them into a new picture in the order of A1, B1, A2, B2 ... An, Bn, and stick them on the plane of the plastic sheet; In this way, when people look from one direction (A, cyan), they will see picture A composed of some pictures of cyan line segments, and from the other direction (B, red), they will see picture B composed of some pictures of red line segments. This is only a schematic diagram, so the two directions A and B are drawn in completely different directions; In fact, due to the refraction of light by the semi-circular plastic sheet, there are many angles to see the two pictures A and B, but there must be an angle to see the picture B between the two angles to see the picture A. In other words, you can see that the angles of the two pictures are spaced from each other.