Robotics Reference
In-Depth Information
a painting into perspective, AARON also needs to know what each lit-
tle patch of the painting represents, what is in front of what, and so on.
When it comes to colouring, for example, AARON is quite likely to find
that a part has been cut up by something passing in front of it, and it
has to be able to find each of the sub-parts so that it can make them
all the same colour. AARON can only accomplish this if it remembers
everything it has done in the painting.
AARON draws its enclosing forms, starting in the foreground, pro-
ceeding towards the background and without erasing anything already
drawn, and most of its decision-making follows from this simple ap-
proach. For example, AARON is unlikely to draw a big object in the
foreground, because it knows that that would obscure any small objects
that it might decide to locate in the background later in the drawing
process. Although the data representing a figure of a person are three-
dimensional, AARON's construction of the representation of a figure is
entirely two-dimensional, which is exactly how a human artist represents
the outside world. In order to create a two-dimensional representation of
a person, AARON was supplied with an extensive set of inference rules
by means of which it could determine which part was in front of which
on the basis of its knowledge of the figure. The problem was simplified
by the realization that the hands move around much more than any other
part of the body, and that a great deal could therefore be determined by
examining the articulation of the arm. For example, AARON can make
the following type of deduction:
if
the left wrist is closer (in three-dimensional space)
than the left elbow
and if
the left elbow is closer (in three-dimensional space)
than the left shoulder
and if
the left wrist is to the right (in two-dimensional
space) of the left shoulder
and if
the left wrist is not higher (in two-dimensional
space) than the right shoulder
then
the left arm will obscure the torso
Such a deduction will lead AARON to the conclusion that the left arm
will have to be drawn before the torso is drawn.
When Cohen started to endow AARON with the ability to colour its
work, the program at first acted as though it was preoccupied with bright-
