Final answer:
The map projection class that cannot be generated using a physical-perspective approach is the Azimuthal projection, unlike cylindrical, conic, and planar projections which can be visualized as the shadow of a globe cast onto different surfaces.
Step-by-step explanation:
Among the principal map projection classes, the one that cannot be generated using a physical-perspective approach is the Azimuthal projection. Physical-perspective projections are based on the concept of projecting the shadow of a wire-skeleton globe onto a geometric surface, such as a cylinder for Mercator projections, a cone for conic projections, or a plane for planar projections.
In contrast, azimuthal projections cannot be created this way because they involve projecting points from the globe onto a plane, typically tangent to the globe at one point, and not by casting a shadow. The principal azimuthal projections, including orthogonal, stereographic, and gnomonic projections, employ the concept of perspective but do not follow the principle of a physical object casting a shadow.
To visualize this, imagine Earth's qualities, such as latitude and longitude, being projected onto the celestial sphere; this theoretical projection is similar in concept to azimuthal map projections. As the Earth is not a point light source but has a span, illustrated by the Sun's size in the sky, a perfect shadow projection is not possible, creating limitations for certain projection methods. The azimuthal projection relies on directly mapping points from the globe to the plane, not on shadow-casting.