1. Draw a new axonometric ellipse, and find out the left and right endpoints in the axonometric direction (draw a line along the horizontal direction of axonometric drawing after passing through the center of the circle).
2. Draw the same axonometric ellipse with its left end as the center.
3. Draw an ellipse with the right end as the center.
4. Connect the left and right endpoints and intersection points of three axonometric ellipses.