The fields of geography and computer graphics must be combined for this
  project to become a practical application. Geography is the study of earth and
  its features. Computer graphics refers to methods of creating visual imagery
  with computing techniques. It is incredibly difficult to interpret hundreds of
  tables of geographic data if it is not visualized (i.e. with computer
  graphics). Thus the combination of geographic data and computer visualization
  techniques is unavoidable.

  There are several applications in use by geographic specialists that help them
  consolidate and visualize geographic data. One such program is called
  ArcGIS{\texttrademark}~\cite{arcgis}. ArcGIS is designed for the desktop
  environment on a typical two-dimensional monitor. It works primarily with
  GIS layer data files (mentioned in Section~\ref{sec:intro}). It is useful
  for portraying and altering region   data and associated attributes. ArcGIS is
  not meant to display three-dimensional data, that task is left to another
  application (typically packaged with ArcGIS) called Arc~Scene{\texttrademark}.
  However, users do not feel immersed into   the environment because the data
  is visualized on a two-dimensional screen.

  The feeling of immersion and realism is important because it allows a
  specialist to notice and analyze more features of a landscape, and to analyze
  those features with higher accuracy. To achieve complete immersion, we use a
  computer graphics technique called Virtual Reality (VR).

  Effective VR is created in a virtual/immersive environment by means of several
  projection screens and accompanying projectors. In this environment, users are
  required to wear a headset or a pair of specialized glasses. Via the
  combination of the glasses, projection screens, and the projectors, users are
  given a realistic sense of depth unattainable on modern desktop systems.
  Several companies such as FakeSpace{\texttrademark} and Silicon Graphics
  Inc.{\texttrademark} sell full VR projection systems.

  Beyond immersion in a VR environment, one must also have the means to interact 
  with and manipulate the data being visualized. For this project, the immersive 
  environment must allow the user to pick regions of a map and see all 
  associated attributes. Attributes assigned to regions in GIS layers depend on 
  the context of the research. The user must also have the ability to add, 
  remove, and update attributes as they see fit, all while inside the VR environment.

  This interaction must be done in real-time, as one of the main points of the
  purpose is to cut-down on a crucial resource, experts' time. For many reasons,
  allowing real-time interaction can be quite difficult. Geographical experts
  need to interact with large areas of the world at once, and the size of the
  area to be visualized is directly proportional to the amount of data stored
  and processed. The second reason is we are striving for realism and the amount
  of realism is also directly proportional to the amount of data stored. This
  all amounts to longer and longer computation time. Optimization methods are a
  must to visualize this data as fast and realistically as possible. We can now
  begin discussing our methods for quickly visualizing this data to allow for
  fluid interaction.