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\begin{document}

\mytitle{10/25/90}

\vspace*{-.25in}
\begin{center} {\large Visual Perception} \end{center}

\vspace*{-.2in}
\prob{1} 

In an information processing system there is the lowest level,
at which raw data is being manipulated. At a higher level, data is more
abstracted with certain meanings attached to groups of raw data. At the
highest level there is total abstraction; all of the lower levels are
combined to form an overall concept. In the case of a hand-held
calculator, the highest level consists of the buttons with symbols on
them that the user presses. These button presses are then converted into
groups of data which represent the symbol of the button pressed. These
data are converted into raw data, probably consisting of logic 1's and
0's, which are manipulated by the hardware (chips and whatnot). 

\prob{2} 

The 2 1/2 D sketch is the interpretation of the primal sketch.
Modules that act on either the raw primal sketch (which has image
intensity values) or the full primal sketch (edges and surfaces) can be
combined to produce the 2 1/2 D sketch. Unlike the primal sketch, which
only has edges and/or image intensity, the 2 1/2 D sketch includes
information such as depth, surface orientation, and shading. However,
unlike the 3D model representation, the 2 1/2 D sketch is
viewer-centered. The 3D model is an object-centered representation,
allowing recognition of objects despite the view.

\prob{3} 

For stereovision, a geometrical constraint, the {\em epipolar
line constraint}, is used to recover the depth of an object from two
images (one from each eye). It narrows down the possible location of a
corresponding primitive in one image for a particular primitive in the
other image.

\prob{4} 

Non-accidental coincidences in speech include pauses separating
words and inflection indicating the end of a sentence. These are
occurrences which allow listeners to easily parse speech, i.e. recognize
words and sentences.

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