How do you visually determine the incline of a hill? How can you determine the form of a piece of cloth just by looking at the pattern on it? How do plates on the near side of a table look different from those on the far side? Elliptical perspective is the primary clue we use to understand and depict the contours and curvature of surfaces and the distance between one surface and another.
This is how elliptical perspective works: If you look at a drinking glass from directly above, the opening, or rim, is a circle. If you look at the glass from the side, the opening appears as an ellipse. If the opening is at your exact eye level, the ellipse is so narrow that it appears as a straight line.
When you raise and lower the glass, the vertical measurement of the ellipse appears to change-in other words, the ellipse appears rounder or flatter, depending on where the glass is in relation to your eye level. So long as the glass remains upright, each step you move it above or below your eye level results in an increase in the vertical measurement of the ellipse
When you look at the rim of a glass so that the opening is almost level with your eyes, it appears as a narrow ellipse. When you look at the rim from directly overhead, it looks like a circle.
This transparent cylinder is divided into four sections that are parallel to one another. Notice how the elliptical shapes that define each section become rounder as they get farther away from your eye level.