N-Body Galaxy Simulation

Very simple, OpenGL & CPU based, nbody simulation written in C. 8192 particles, O(n^2) operations.

Category:

Science & Technology

Tags:

• body
• particle
• galaxy
• space
• simulation
• visualization
• opengl

[VelRyphon]

Is it a 2D or 3D simulation ? I'm working too on a cosomoligcal simulator, for now I'm still in the 2D configuration, but I don't get any main rotational behaviour like yours, even with collision handled with SPH. I use the Barnes Hut algorithm to accelerate gravity computation. Could you give some details about your implementation ? Thanks.

[rdelcueto]

@VelRyphon It's 3D simulation, based on the model specified @ Nvidia's Nbody Paper (Google for the PDF and source code). It's quite a simple and naive simulation. (Uses no data structures simplifications, nor collision detection). I'll say your simulator is way more complex and interesting, in that sense.

I initialize my particles inside a two ellipsoid constrained space, and specify a speed vector in such way they all orbit in the same direction, to create the spiral rotation behavior.

[TheJesseLenney]

Is there a black hole in the middle, or are you just doing the n^2 operations? Also, How come there are no wild slingshot particles (when 2 particles get really close together).

[rdelcueto]

@TheJesseLenney There's no black hole in the simulation, just the n^2 interactions between the n particles. To prevent the "wild slingshots", a smoothing factor is used, so that particles are never TOO close, and you can control the "slingshot" speed. Without it, you get a very erratic behavior, were most particles fly away from the galaxy center and never come back.

[SomeHelpNeeded]

Is this video in real-time, or did you speed it up?

[rdelcueto]

@SomeHelpNeeded No realtime here (8192 particles). =)

On my Intel i7 @ 1.6, using 4 threads, it renders @ ~1fps.

[tclyue]

@VelRyphon Have you had any success implementing Barnes & Hut algo?

[DKM101]

@VelRyphon MASSIVE BUMP but it looks like a good source of inspiration is youtube com/user/Nbodyshop

they have "big-bang" style starts, along with some SPH stuff to accurately model gasses.

[ColacX]

how big is the diffrence between the smallest mass and biggest mass?

[ColacX]

i dig this nice question and nice answer was having problems figuring this out

[VelRyphon]

@rdelcueto Ok thank you. I saw this NVidia paper. Indeed it's quiet a simple model. you're swirling rendering comes from your initial conditions, having already an orbiting rotation before you lauch it. I'm trying to get that rotation from scratch, with 0 velocity at beginning, only random positions in a sphere which induce gravitation interaction...