By Chris Worman and Andrey Mirtchovski

trexpeeverΛογισμικό & κατασκευή λογ/κού

13 Δεκ 2013 (πριν από 3 χρόνια και 10 μήνες)

66 εμφανίσεις

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
c
i

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