Painting 1. Draw a cube, a square on the front and a side. Draw a three-dimensional hidden surface with dotted lines, and choose gray to draw shadows.

Painting II. Draw a cuboid, draw the front and draw the side. Draw a hidden face with dotted lines and a shadow with gray.

Painting 3. Draw a sphere and a circle with the help of compasses. Draw a cross section and draw its shadow and dark side.

A three-dimensional figure is a geometric figure whose parts are not in the same plane, and it is surrounded by one or more surfaces that can exist in real life. Points become lines, lines become faces, and faces become bodies. That is to say, when you look at a regular three-dimensional figure such as a cuboid or cube, you can see at most three faces of the three-dimensional figure.