Contour81
This is an Educational Game
Mactivity's CD-ROM nr 10 advice: This application did
run on a b/w 68030 processor under System 7.1, but
the behaviour on a ColorScreen of a PowerMacintosh
running System 7.1.2 was not satisfying. Our advice:
use only on 68030 processors, or try with caution
on a 68040 processor
Contour81 is an application that creates contour maps
and pictures from lists of three-dimensional data.
A contour map is a two-dimensional picture of a surface
defined by a set of data points. The points would usually
be elevations of a physical location, such as a planned
construction site. A survey crew would go to the site
and essentially return with (among other things) a
list of "points". Each one of these points
would specify the elevation of some location at the
site. Then, an engineer or draftsperson would have
to plot the points and draw contour lines according
to general rules of thumb. These contour lines would
then represent locations at which the elevation was
constant. A person could walk along the line and not
move up or down with respect to a reference elevation
at all. The site engineer can look at this contour
map and calculate the volumes of various areas defined
by the contour lines. In the case of site development,
this tells him or her how much earth must be moved
from one place to another in order to change the topography
of the location into an acceptable form. A hydrologic
engineer could look at the map and tell where flood
areas would occur and the way that water would move
around the site in a rainstorm. For example, water
always seeks the lowest level as quickly as possible.
Therefore it would flow perpendicular to the contour
lines (the gradient), because that is the quickest
way for it to change its elevation. Another type of
contour map might be a scientist's plot of the electric
potential (voltage) in an area of space. Then the contour
lines would define equipotentials, a loose definition
of these being lines that a charged particle could
move on without changing its energy. In this example,
if we draw lines perpendicular to the contour lines,
these represent the electric field.
In case you haven't guessed already, the process of
drawing these contour maps by hand can be extremely
tedious and time-consuming. Until the relatively recent
advent of low-cost microcomputers, however, this was
(and still is) the only way available to some technical
people. This program provides the necessary mathematical
and graphic power in an simple, low-cost application
that adheres to the Macintosh(TM) User Interface Guidelines.
We must assume that you are familiar with basic Macintosh
operation and are knowledgeable about the meaning of
your three-dimensional data and its analysis. You do
not have to understand any of the mathematics behind
the program if you do not wish to, but a full explanation
of the process is provided for those who are interested.
Please also note that the generation of hard copy from
this program also requires the use of MacDraw(TM),
AutoCAD(TM) or another program that can read and work
with PICT or DXF(TM) files.
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