The Perspective of a Circle
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A circle in perspective is called an ellipse. The drawing of ellipses is controlled by rectangular perspective.
Our drawing above of an ellipse illustrates this technique. There are two distinct stages in its creation:
fig.1. The circle is first visualized in plan form on a flat square grid. Each section of the grid contains one quarter of the circle.
fig.2. The square grid is distorted according to the laws of perspective. The circle is then redrawn onto the distorted grid to create an ellipse.
The diagonals of the grid have been drawn in yellow on both illustrations to help with the plotting of the circle and ellipse.