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By Chris Worman and
Andrey Mirtchovski
Why Galaxies?
• Interest in scientific computation and
simulation
• Visually appealing results
• To learn how to model gravity based
systems
Galaxy Collision
• A galaxy is modeled as a grouping of stars
around a massive body
• Only stars with a velocity that is less than
the escape velocity will remain in the
galaxy:
Velocity
• If the velocity of a star is too low then it will
be sucked into the center of the galaxy
• The direction of the velocity should also be
tangential to the desired orbit
Gravity
• If a body A of mass m is at a distance of r
from a body B of mass M then
Where G is the gravitational constant
Gravity
• This implies that the acceleration in the i-th
component ci is given by
2D Results
• Initially the simulation was implemented in
two dimensions
• The following slides depict a collision
between two galaxies
• The galaxy on the top of the screen is the
more massive of the two
• There are 10,000 stars per galaxy
Challenges in 3D Implementation
• Computationally expensive
– O(n^2) or O(n*log(n)) minimum
– Scientific simulations run on 256+ processor
machines
• Memory requirements
– Based on design and number of galaxies
memory requirements can grow up to gigabytes
• Visualization – creating a visually appealing
galaxy
Galaxy Collision Realism
• Very close to real-life galaxy collisions
• Compare a two-galaxy collision with
images taken from Hubble Space Telescope
3D Results
• Due to the extreme computation
requirements for the 3D version, real-time
galaxy collision is limited to about 500 stars
per galaxy
• The following slides depict a 3D galaxy
collision with 1000 stars per galaxy
Expandability
• Both 2D and 3D models could be extended
to more than 2 galaxies.
• Number of stars per galaxy can vary
• Galaxy masses vary
• Simulation of different celestial objects
(quasars, black holes, etc)
Conclusion
• Java3D is a viable tool for creating
scientific simulations and visualizations
• Performance losses from using Java3D are
relatively big compared with pure OpenGL
• Development time is significantly less, due
to higher level abstraction of Java3D’s API
• NASA officials have already contacted us…
(which leads us to ‘Future Plans’)
Future Plans
• Over the next 5 years we plan to run a 3D
simulation of 2 galaxies with 100 000 stars
each. We plan to complete a 500-frame
movie by the end of the run.
• Simulate evolution of stars, galaxies and
solar systems
• http://research.amnh.org/~summers/mihos/
mihos.html