In Other Words The Observer Simply Points In The Same Direction As The Lines In Order To Find Their Vanishing Point

[30] Why The "Parallel Pointing" Method Of Locating Vanishing Points Is Important

In T-square and triangle perspective, this method of locating vanishing points is an essential step.

Thus, to draw the object below, we first construct a top view or plan (left), showing the object, the picture plane (seen as a line) and the observer's position. On this plan, "sight lines" pointing parallel to the object lines are drawn to locate the vanishing points on the picture plane. Other sight lines "project" the object itself onto the picture plane. The picture plane line, therefore, shows the relationship of the object's apparent size to the vanishing points. This "measurement line" is then transferred to the actual picture (right), where it is superimposed on the horizontal vanishing line (eye level). Whether the subject is now drawn above, below, or straddling this line, the relationships remain the same.

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Diagram Foreshortening

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In freehand drawing, whether from life or from imagination, this procedure naturally is inapplicable. The convergence of lines, foreshortening, etc., must instead be determined by careful observation or visualization.

Yet in this book the figure of an observer pointing toward a picture plane parallel to object lines will be shown repeatedly, in order to emphasize the importance of the observer-to-subject relationship even for freehand drawing.

The observer's viewpoint and cone of vision, his distance from a subject, and the apparent direction of the subject's lines are the principal determinants of how things appear in real life and therefore in perspective drawing. As these factors change, so will the picture. This is the key to any "system" of perspective drawing. Becoming aware of it and understanding it will strengthen your powers of visualization and observation.

Nature's Horizon Always Appears At Observer's Eye Level. Therefore, It Can Be Used As The [31]

Vanishing Line For Horizontal Lines

In other words, if the observer is on a mountain top or descending in a parachute the horizon line will appear on a level with his eyes.

Eye Level Horizon Line

In other words, if the observer is on a mountain top or descending in a parachute the horizon line will appear on a level with his eyes.

And when the observer is on flat ground the horizon line will still appear at his eye level. (In this case, though, notice that the amount of ground before him seems less than the amount seen from the higher level.)

And if the observer lies on the ground the horizon line will still appear at eye level. (But notice that here the amount of ground area leading to the horizon line seems even less than in the above two views.)

Mountain Horizon Line

In fact, nature's horizon line, whether visible or concealed (by these mountains, for instance, or by a house, trees or people), will always be at the observer's eye level. The eye level, we have seen, is the vanishing line for all horizontal lines. Therefore, this line, which is both eye level and nature's horizon, is of great importance, for on it are located the vanishing points of all sets of horizontal lines.

[32] Why Nature's Horizon Appears At Observer's Eye Level — Theory

NATURE'S HORIZON LINE: (i.e., where the sky appears to meet the ocean, prairie, or desert) is technically slightly different from observer's eye level. The eye level plane is truly horizontal (i.e., constantly perpendicular to the line of the observer's body) while the earth actually curves away from the observer in all directions. The diagram shows this, but with tremendous exaggeration.


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