Graphics Reference
In-Depth Information
NURBS geometry is most commonly used. For characters and other complex
organic subjects, either digitized geometry is used, or drawings made of the subject.
In the case of drawings, they are approximations, and rely heavily on the skill of the
artist who makes them and the ability of the modeler to interpret them.
4.2.5
Calculation
Measuring by calculation can involve working backwards from an existing object
or working forwards as part of the design process. Working backwards can be as
simple as basic multiplication and division (Hildreth 1983 ). For example, if you
have fi ve equally-spaced windows on a wall, with a space of half a window span
between them and on either side, and the total width is 100, then each window is
100
52 6 2125
*
=
.
units wide. If you don't know how wide the wall is, you can
(*)
+
use fractions instead. The smallest unit is the span between windows, so it can be 1
“wall unit”. There are four spaces between the windows and one on either side of
the outermost windows for a total of six. There are fi ve windows, each of which
is 2 units wide, for a total of 10. 10 + 6 = 16, so the wall is 16 units wide and the
windows are 2 units wide. Without knowing the actual dimension of the wall units,
the model can still be made accurately as long as each wall unit dimension is
consistent with the rest (Figs. 4.6 and 4.7 ). This type of measuring has been in use
for thousands of years and relies heavily on proportions , or the relative size or
magnitude of any two items to each other, or of any part of an item to itself.
Another way to calculate doesn't require the use of numbers or math. Instead,
objects can be designed or subdivided graphically by using squares, circles, and
triangles. This method was used by architects in ancient times (Fig. 4.8 ), particu-
larly for the designs of churches (Carpo 2003 ). For many architectural subjects,
a geometric analysis combined with a single linear dimension (usually total height
or width of a structure) is enough to generate an accurate CG facsimile of the original.
4.2.6
Relative and Absolute
Absolute dimensions are measurements made against a fi xed standard, such as an
inch or a centimeter as represented on a measuring device. Comparing one thing
to another is a relative measurement. In CG, a relative measurement can be just
as accurate as an absolute measurement, because within a CG environment, all
measurements are based on a fi xed standard imposed by the software.
Outside of a computer, some people use a casual standard for relative measure-
ments. For them, things are “big”, “small”, or “average”. Robert Wadlow then, is not
8
tall, an absolute dimension ; instead, he is “tall”. The result of measuring in this
way is that gross exaggerations take place. If something is “tall” it is made too tall.
11.1
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