Of course, you must have some spatial imagination. In addition, descriptive geometry also gives the relationship between such figures, which can be known by reading a book carefully. Include drawing an axial side perspective view by use a plan view.

1. To draw a three-dimensional diagram, you must first prepare a piece of paper, a ruler, a rough pen and a pencil.

2. First, put the cap of the thick pen on the paper and draw a circle in the middle of the paper with a pencil.

Draw many horizontal lines around the circle with a pencil and ruler, and the spacing of each horizontal line is the same.

4. Draw several arcs on the circle with a pencil. The two ends of the arc should be connected with the horizontal lines on both sides. From top to bottom, the distance between arcs is wider and wider.

Draw a shadow on the right side of the circle with a pencil. From the edge of the circle to the right, the shadow is getting lighter and lighter.

6. Then draw a shadow on the left side of the circle with a pencil and paint it evenly.

7. Draw a shadow on the right side of the circle with a pencil and paint it evenly. Now the circle has become a sphere.