Theatre Design & Technology - Summer 1981 - 41

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,goo

3bo"

Z.70 0

Figure 21

Space is conceived as curved in the measured grid (Fig. 20).
Unlike the freehand grid that requires the designer to make
estimates from the perspective grid, the measured grid allows
precise measurements. The designer projects points from the
floorplan onto the picture cylinder. These points are transferred to the measured perspective grid as vertical lines. The
vertical dimensions of these lines are determined by the formula:

-=_.

When the drawing is to one of the sizes suggested in Figure 7, the
engineering scale can be used to simplify the computation because
d' is always 100.
100 X ~
d = s' .

This computation for the four lines in this example is shown
left to right below. A calculator is used for rapid computation:

x --2

100

x --

This method is illustrated by two examples.

Drawing the Scenic Elements on the Measured Grid
In addition to aT-square, triangle, and French curve or adjustable curve, an architect's scale, an engineer's scale, and
a pocket calculator are needed for measured perspective.
An architect's scale is needed only if the floorplan is at an
unusual scale. The engineer's scale will be useful for standard
1/2" = l' and 1 / 4" = l' scales. The 20 scale and the 40
scale coincide with these standard scales making it unnecessary to convert inch increments into decimal fractions before
calculating.
The palace (unit 4), which was developed on the freehand
grid by turning the grid beneath the tracing paper drawing
(Fig. 18), can also be developed on the freehand grid (Fig.
21). The drawing is developed in four steps.
1. Find the position of the verticals from the f1oorplan. To do this,
project the corners of the plan drawing of the building to the picture
cylinder in plan.
2. Find the position of the verticals in the perspective. To do this
transfer the position of the marks from the plan view of the picture
cylinder to the measured perspective grid. The marks are drawn as
vertical lines on the perspective grid.
3. Find the length of the four verticals from the f1oorplan. To do this,
use the formula

s'
s
-=_.

USITT /Summer, 1981

5
15.

100

32.9

5
= 48.8
10.25

5
100 x - - = 29.9
16.7
100

5
= 40.3
12.4

x --

These four products are measured with the appropriate engineering scale from the horizon along the respective verticals.
In this case, the measurements above and below the horizon
are the same because the figure is symmetrical.
Note: All measurements using the engineer's rule are measured from the horizon line.
4. The figure is complete when the top and bottom of the figure is
drawn. The use of appropriate vanishing points and a French curve
is an aid in drawing the curved lines. The vanishing points for an
object in curvilinear perspective are found by referring to the fJoorplan. A line through the station point, parallel with the sides of the
object, establishes the vanishing point of the sides. These points
are transferred as degree marks from the plan to the perspective.

The Hell Mouth (unit 3) is another example of a figure that is
awkwardly developed on the freehand grid (Fig. 17). The difficulty here does not arise because the figure is not on the axis
of the freehand grid, but because it sits on a portion of the grid
that has been cut off by the 60° band of vision. When measured perspective is used, only the portion of the figure that
Theafre Design & Technology

Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1981