Final answer:
Explaining one-point or two-point perspective using a sphere is difficult because these perspectives rely on straight lines and vanishing points, which a sphere lacks due to its uniform shape. While multiple spheres of different sizes can convey depth, they still do not offer the straight edges required to illustrate linear perspective.
Step-by-step explanation:
It would be difficult to explain the difference between one-point and two-point perspective using a single round object like a sphere because linear perspective relies on straight lines that converge at vanishing points on the horizon, which are not present on a round object. A sphere appears the same from every angle, making it impossible to depict the convergence of lines which is crucial in illustrating perspective. With multiple spheres of different sizes, however, you could use size variation to imply depth in a method akin to atmospheric perspective, which suggests distance through size, color, and clarity changes without relying on linear perspective.
For instance, in one-point perspective, lines converge at a single point which can not be illustrated with a sphere since it has no edges to converge. In contrast, two-point perspective involves two vanishing points and is used when an object, such as a cube, has edges receding into the distance in two different directions, which a sphere also cannot demonstrate.
Therefore, while you can suggest spatial depth using spherical objects through atmospheric perspective, the concepts of one and two-point perspective, which are based on the convergence of straight lines, are demonstrated more effectively with objects that have clear linear dimensions, like buildings or boxes.