Besides the more usual angular perspective there is the bird's-eye per spective, when the eye is taken up to an imag inary high level: the curvilinear or panoramie perspective, in which the surface of projection is a concave cylinder: and the oblique perspective. with its triple horizons and vanishing points.
Aerial perspective consists in a modulation of the brightness and colors of objects in accordance with the state of the atmosphere, the depth of the body in the perspective plane (i.e. distance in nature from the ground line), and other acci dents of place and time. As the distance of ob jects increases. their illuminated parts are made less brilliant, and their shaded parts more feeble. The bluish tint imparted by a large mass of the atmosphere to the bodies seen through it is fre quently imitated by the mixing of a slight tint of blue with the colors to be applied; a yellow object thus assumes a greenish tint:•a red one a violet tint, etc. The air, when charged with vapor, is represented by a diminution of the brightness of colors, and by the grayish tint im parted to them.
Architectural perspective is simply the appli cation of linear perspective to architectural draw ing. The plans, elevations, and sections by which buildings are represented in the working draw ings are orthographic projections, which give the correct geometric and dimensional relations of the various parts of the building shown, but pre sent in each ease only two dimensions, and do not exhibit the natural aspect of the structure as it appears to the eye from any given point of view. This deficiency is supplied by the perspectives, which show its appearance as seen from one or another point of view, all three dimensions being represented, but with the foreshortenings and an gular distortions of its actual appearance from the given point. It is customary to make per spectives not merely of the exterior of a projected or executed building, but also of the more impor tant interior portions. See DRAWING.