Selected Bibliography Architectural Graphics | Page 113

TWO -POINT PERSPECTIVE The two-point perspective system assumes t hat the observer's central axis of vision (CAV) is horizontal and the picture plane (PP) is vertical. The principal vertical axis is parallel to PP, and all lines parallel to it remain vertical and parallel in the perspective drawing. The two principal horizontal axes, however, are oblique to PP All lines parallel to these axes therefore appear to converge to two vanishing points on the horizon line(HL), oneset to the left and the ot her t othe right. T are the two hese points referred to intwo-point perspective. Two-point perspective is probably the most widely used of the three types of linear perspective. Unlike one-point perspectives, two-point perspectives tend to be neither symmetrical nor static. Atwo-point perspective is particularly effective in illustrat ing the three-dimensional form of objects in space ranging in scale from achair to the massing of abuilding. • T pictorial effect of a two-point perspective varies he withthe spectator's angle of view. The orientation of thetwo horizontal axes t oPP determines how much we will see of the two majar sets of vertical planes and the degree to which they are foreshortened in perspective. • In depicting a spatial volume. such as the interior of a room or an exterior courtyard or street. a two-point perspective is most effective when the angle of view approaches that of a one-point perspective. PERS PECTIVE DRAW INGS I 107