Measurements and Their Relationship to CG - An Introduction to Computer Graphics for Artists - page 50

Table 4.1 Dimensi oning options

Direct Existing Estimate Design

Ruled Blueprints Partial dimensions Design from scratch

Protractor Contour map Confl icting reference Design from source

Micrometer Site map Photo reference Design from style

Scanner Historical reference Visual observation Design from rules

Digitizer Images Geometric subdivision Calculation

Surveyed Calculation

meaningful if they consistently refer to the same subject and measuring unit. The
ratio of one measurement to another is called proportion (Solomon 1987 ). When
the proportions of your measurements are inconsistent, the resulting object will be
a weak likeness. Even when designing non-existent objects, if proportions are
inconsistent with real world examples, they will be unconvincing (Doczi 2005 ).
This is why it is important to always have a fi xed standard against which you
may test your measurements (Birkett and Jurgenson 2001 ). One way to do this is
to decide that everything will be measured in centimetres and then use the same
measurement device for every measurement made. Once you have made this
decision, you can measure your target object against the units you chose for that
object class. The result will be accurate measurements and proportions that can be
used to construct a good likeness of the target object.

4.2 Dimensions

Architects and engineers call the process of acquiring or recording measurements
dimensioning and measurements are referred to as dimensions (Morandi 1962 ).
These terms have been adopted within the CG art community, and are used inter-
changeably. Because the quality of dimensions is crucial to achieving a likeness, it
is important for artists to secure the most accurate dimensions possible. This can
be done in a number of ways, all of which come down to direct measurement,
acquisition of pre-measured dimensions, estimation, and design. Table 4.1 provides
examples of some of the variety available within each of these methods. CG artists
will fi nd that they must often use a combination of methods because it is not always
possible to gain access to their target object.
Notice that in the estimate column of Table 4.1 , every estimate is based on
something specifi c. This is because an estimate isn't simply made up; it is an attempt
to arrive at the best answer based on the best available information.
Sometimes estimates, existing data, or designed measurements come in the form
of images. The resolution of these images can affect the accuracy of the information
they contain. If the width of a pixel in the image is equal to or greater than a meaningful
dimension in the target, all smaller objects will appear to be the same size, though
they may be much smaller. When this happens, artists have a tendency to build to the