Orthographic projection is the shadow of the object when the light hits the plane vertically. According to the topic, it is easy to prove that plane A 1BC 1 is parallel to plane ACD 1, that is, it is parallel to plane A. It can be concluded that the projection lengths of the three sides next to B 1 on plane A are equal, and drawing can be started, that is, it is divided into three with B 1 as the center. Because the three sides connected by point B 1 are parallel to the other sides, it is easy to make three congruent diamonds. After connecting ACD 1, since the plane ACD 1 is parallel to the plane A, the projected edge and the actual edge are the same and equal, which can be directly calculated. According to the nature of the diamond, it can be seen that each side of the triangle ACD 1 divides the area of each diamond into two halves.