Theatre Design & Technology - Summer 1981 - 38

:2"7Tr

0"ot.?
",0/-

........

I I

I
I

I
:

Figure 13

'"c

I
~

/ ~I
1

Freehand Grid Adjustments

Drawing the Measured Grid

It may be desirable to develop a special freehand grid for
specific circumstances, but this limits the application of the
grid to the specific theatre. For example, a low-hanging light
grid that is in four foot units may be so prominent in the
theatre that four feet seems an ideal unit for a drawing grid. In
another example, a high or low average viewing position may
suggest a shift in the horizon level. All that is needed in these
situations is to change the horizon level or the scale of the grid
units in the 90° perspective that is used in developing the curvilinear grid. These adjustments, although helpful in specific
situations, limit the grid to one application. The freehand cylindrical perspective grid has almost universal application
when it is used together with measured perspective. For example, if a three foot rather than a five foot horizon is required, the bottom grid represents a plane two feet below the
floor of the theatre and cannot be used directly as floor. But
as few as four calculator computations can establish the
raised position of the corners of the room. The grid lines, although not representing the floor surface, can serve as a
guide in interpolating a new floor grid in far less time than
drawing an entirely new freehand grid. These adjustments
seem reasonable after some experience drawing on the standard freehand grid. Only when the room has walls that are not
straight or not at right angles to one another should the standard freehand grid be set aside. In this case, only the measured perspective grid is used as a drawing guide.

The measured grid is based on a cylindrical conception of
space (Fig. 20). The increments shown as horizontal lines represent circles in plan and the thirty-six vertical segments represent 10° segments in plan.

Figure 14

:.. PA

",OISe:

TEMF... E.

The measured curvilinear perspective grid is developed
from the 90° perspective as follows (Fig. 13).
1. Form the cylinder by the formula 21Tr.
2. Project depth increments by T-square from the 90 0 perspective.
3. Divide the cylinder into thirty-six 10 0 segments.
4. Project the 60 0 band of vision from the 90 0 perspective onto a
cylinder.

This grid allows precise horizontal measurements from
plan. Because of its simplicity it can be used in combination
with the freehand grid without confusion. The two grids, if
constructed on tracing vellum, can be placed one on top of
the other. The measured grid is used alone when few elements in the theatre fall on right angle co-ordinates. This is
useful, for example, when the walls are not flat planes, or do
not form right angles with one another.

Developing the Design on the Freehand Grid
The hypothetical design is suggested by a miniature of the
Valenciennes' Passion Play. Separate structures are placed at
the periphery of a small black box theatre. It is imagined that
the audience stands, moving as the action changes location.
For purposes of demonstration it is assumed that the designer has some idea of what the separate structures will look
like and where they will be placed. The perspective will serve
as a check on how the elements visually relate to one another.
A French curve or an adjustable curve are needed in addition to aT-square and triangle so that precise arcs can be
drawn.

---5'_ _

Preparing the Floorplan
Prepare a grid in 5' scale units on a separate sheet of tracing paper. Mark one intersection of 5' units as the station
point (SP). Adjust this grid so that the station point is in a desirable place and the grid lines coincide as much as possible
with the walls of the theatre. In this example all but one of the

Figure 15

Horizon Line

Ground Line
1 Ocean

2 Paradise

3 Hell Mouth

4 Palace

5 Temple

6 Paradise

Temple

Theatre Design & Technol09Y

USITT /Summer, 1981

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