Elementary perspective arranged to meet the requirements of architects, draughtmen, and students (1913)
Crosskey, Lewes R · London, Backie and son ltd · leaf 18
ne along which the spectators sight is most acute, and an object is onlyseen when it comes within the cone of rays. In perspective the spectator is invariably supposed to look in a direction perpen-dicular to the P.P., hence the spectators C.V.R. is perpendicular to the P.P. Itfollows that the… … Pig. 10. Fig. 10 illustrates the cone of rays intersected by the P.P. The size of this angle varies with different people, but by experiment it has been found that 60°is the greatest angle that can be employed in order to distinctly see all the field within the angle. ELEMENTARY PERSPECTIVE.…
Perspective
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