Recursive Ray Acoustics (RRA) Sonar Algorithm
Java-VRML Implementation
This project calculates and renders physically realistic sonar beams in real time.
Java programs are used for sonar ray-tracing computation and the Virtual Reality
Modeling Language (VRML 97) is used for 3D graphics.
The primary motivation for this project is to produce underwater sonar beams
for analytic and visualization use in virtual worlds.
Virtual world simulations are realistic when individual components
are simulated in a manner that reflects reality. For an underwater virtual
world that includes simulated acoustic detection, a physically based sonar propagation
model is required if ranges in excess of tens of meters are expected.
The Recursive Ray Acoustics (RRA) Algorithm by Dr. Lawrence Ziomek of NPS
provides a general & rapid ray-tracing algorithm which can accurately
& quickly predict sonar propagation through seawater, under a wide variety
of surface, water-column and ocean-bottom environmental conditions.
This project creates an application programming interface (API) for real-time
3D computation and visualization of acoustic energy propagation. The API
provides features for generating complex physically based sonar information
at interaction rates, and then visualizing that acoustic information.
The simulation is programmed in Java, and runs either as a stand-alone
program or as a script in a web browser. This program generates Virtual
Reality Modeling Language (VRML 97) compliant code that can be viewed
from any VRML-capable Web browser. This approach allows the characteristics
of the energy propagation to be calculated with high precision and observed
in three dimensions (3D) and in real time.
As sonar-system information bandwidth becomes larger, more intuitive ways of
presenting information to users are required. Interactive 3D graphics with
environmental and entity rendering can free users from mentally integrating
complex data piecemeal. This approach can enable significantly greater understanding
and quicker reaction times. We are optimistic that this API might someday provide
the foundation for fundamental advances in sonar modeling and visualization.
The RRA software, model and documentation library was last updated
20 September 1999.
Confirmation of build date/time is in file
build.date.rra.txt.
The software library is available in two forms:
rra.tar.gz
and
rra.zip
A
Makefile
is used to produce the rra distribution.
See the text file
make_rra.out
for a log of success, warning & error messages generated
during this build.
Autogenerated VRML file warnings are also available at
filelist.vorlon.warnings.out.
The
RRA Package Documentation
is produced by
Javadoc
from the API source code.
It describes rra model classes and example applications in the RRA package library.
The
References
section on this page includes links to Tim Holliday's thesis and summary powerpoint presentation.
Here are a few simple visualization examples.
We have chosen a single but challenging sonar geometry
to demonstrate a variety of visualization techniques.
Each ping starts at the surface and points down towards an upward-sloping bottom.
Each ping reflects between shallow bottom and water surface several times before
returning dowards deep geometry. Refraction (bending) and energy absorption occurs
throughout the ping trajectory, due to continuous changes in
sound speed profile (SSP) plus reflections at bottom and surface.
The great variety of displayed information in the following examples
hint at the visualization possibilities possible using this approach.
A great deal of follow-on work is planned.
Holliday, Timothy, Real-Time 3D Sonar Modeling and Visualization,
Master's Thesis, Naval Postgraduate School, Monterey California,
June 1998.
Available at
HollidayRRAthesis.pdf.
Slideset available in
Powerpoint
and
Acrobat .pdf
formats.
Ziomek, Lawrence, "The RRA Algorithm: Recursive Ray Acoustics for Three-Dimensional Speeds of
Sound," IEEE Journal of Oceanic Engineering, vol. 18 no. 1, January 1993.
Ziomek, Lawrence, Fundamentals of Acoustic Field Theory and Space-Time Signal Processing, First
Edition, CRC Press, Boca Raton Florida, 1995.
The RRA work is currently unfunded but remains in use for student projects.
Significant additional development is possible.
Please contact
Don Brutzman
if you are interested in research sponsorship opportunities.
Students in our research team at NPS are carrying out a variety of related work
on large-scale networked software architectures.
Topics include implementation of the
Distributed Interactive Simulation (DIS) Protocol dis-java-vrml,
dial-a-behavior protocol (DABP),
area-of-interest management (AOIM) and the
virtual reality transfer protocol (vrtp).
1 November 2003
(official NPS disclaimer)
URL:
http://web.nps.navy.mil/~brutzman/vrtp/rra
feedback:
brutzman@nps.navy.mil
