Optical Corrections on Rooves
Optical Corrections. The effect of distance from the eye or foreshortening must be constantly borne in mind in designing any structure.
The appearance of the finished structure can only of course be gauged by experience gained in actually designing and carrying out previous buildings, and by the intelligent study of old buildings. It can readily be understood, however, that a sloping-roof will in appearance be much lower in execution than on a geometrical drawing, in consequence of the ridge being much further from the eye than the eaves.
From the time of the Greeks optical corrections have been employed in architectural design, and these corrections have to be considered much more thoroughly in larger buildings than in those we are now dealing with.
There are, however, occasions when they must be borne in mind even in smaller buildings if a satisfactory result is desired, as, for instance, when using long horizontal beams, which always appear to drop in the centre unless slightly cambered.
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