MarsMap: Analyzing Pathfinder Data using Virtual Reality
C. Stoker, T. Blackmon, J. Hagen, P. Henning, B. Kanefsky, C. Neveu, 
D.Rasmussen, K. Schwehr, M. Sims, E. Zbinden
Intelligent Mechanisms Group
NASA Ames Research Center, MS 269-3
Moffett Field, CA
94035-1000
USA 

Abstract

The Pathfinder mission made use of a unique capability to rapidly
generate and interactively display three-dimensional Dphoto-realistic
virtual reality (VR) models of the Martian surface.  Marsmap, the
interactive terrain visualization system developed for Pathfinder by
the Intelligent Mechanisms Group at NASA Ames as part of a
participating science project, creates and renders digital terrain
models produced from stereo images of Mars surface taken by the
landers IMP camera. An automated machine vision algorithm produces
dense range maps of the near visible field by matching features in the
left and right IMP camera images using the known camera geometry. The
resulting range maps are then projected into a three-dimensional model
as a connected polygonal mesh. IMP images or color composites are then
e Coverlaid onto the mesh as textures to provide photo-realism in the
model. Upon receipt at NASA JPL, IMP images were shipped to NASA Ames
Research Center via internet where models were computed and then
shipped back to JPL for display. The time from receipt of image data
to display of complete models was less than 30 minutes.

The VR models are viewed interactively using an interface that allows
reprojection from any perspective driven by a standard three-button
computer mouse. Terrain models are rendered at a frame rate of up to
60 frames per second using a Silicon Graphics Onyx 2 computer,
allowing the user to move smoothly though the interactive model
environment. The model can be viewed on a monitor either mono or
stereoscopically, or using a head-tracked VR display. The VR model
also incorporates graphical representations of the lander and the
sequence and spatial locations at which rover data were taken. As the
rover moves, graphical models of the rover are added for each position
that can uniquely determined using stereo images of the rover taken by
IMP.  Images taken by Sojourner are projected into the model as
two-dimensional billboards to show the proper perspective of these
images. Distance and angle measurements can be made on features viewed
in the model using a mouse-driven three-dimensional cursor and a
point-and-click interface.  The VR model was used to assist with
archiving and planning on Sojourner activities. It is also used to
make detailed measurements of surface features, such as wind streaks
and rock size and orientation, that are difficult to perform using
two-dimensional images.

Abstract of Paper presented at American Geophysical Union, Fall Meeting, San Francisco, Dec. 9, 1997.