How much can ten minutes of physics change when gravity is invited?
Ten Minute Physics
11–20 of 43 posts
Re: Ten Minute Physics
#12interesting ideas but too short. 100 minutes would be better.
Re: Ten Minute Physics
#13Ten Minute Physics is a great resource! Matthias Mueller makes concise demos and explains them really well. (Though I think it would take someone without existing familiarity with the subject matter a lot longer than 10 minutes to digest the results. Lots of rewatching!) A really interesting results that's come out of Matthias and co.'s research in the last few years that is still percolating its way through the real…
This is very coincidental timing. The physics simulation in the Source game engine, and Garry's mod, absolutely cemented in me an interest in computational physics. I really wanted to see fully simulated fluid water in games, particularly GMod, but it never really happened, 15 years ago.
This never stopped bothering me, so I recently loaded up the game and programmed an entity that was simply a particle that repelled itself with inverse distance-squared falloff. I was only able to get up to around 100 particles before the game slowed from 200+ fps to ~10. There seemed to be a huge amount of overhead in the lua scripting system's connection to the game/physics engine. Something about getting the position of 100 particles, or asking for all the particles within a given range of each particle, even for only 100, was enough to send frametimes over 100ms-1000ms. I wanted at least 500-1000 particles at at least 10fps, and I'm sure in terms of raw math, that is nothing for modern CPUs, even with the most naive implementation. I had to figure out exactly which lua functions had the most overhead for such a small amount of simple math.
So, I re-wrote the script, seeking to chase every rabbit hole that would let me increase the number of particles while maintaining over 10fps.
1. Switch from per-particle loop, to a global loop that cached each particle's position per frame, so it was more pure math and less engine bindings/"context switching". Approx 50 particles to approx 150.
2. Limit the particle simulation to 10hz instead of 66hz+, and adjust the force scale to compensate. Raised the limit to approx 300-400 particles.
3. A dynamic scaling system, so that the system would never try to simulate more than 100 particles at once, per 10hz tick. Raised the limit to approx 700 particles.
At this point, there are now other non-CPU bottlenecks. Any method of drawing 700 entities, even basic wireframe?, even with a very high end GPU on a nearly 20 year old game, is significant, and there's no easy way for me to break past this.
I am sure if I learned how the source engine's plugin system worked, and I hooked into the physics engine using C++ instead of however the lua bindings work, I should be able to simulate a thousand particles at 100+fps, but that's about where the scope of the project starts to contend with "real life", and I continue to wait for a 3D sandbox game with satisfying fluid physics.
Your optimization method of "only one iteration per frame" is in a sense, the same, and in a sense, the opposite of my method of simply not even simulating every particle every frame... I just didn't have the spare performance for that. Then again, I'm only simulating a single force field with no proper collision detection or anything fancy
Re: Ten Minute Physics
#14Ten Minute Physics is a great resource! Matthias Mueller makes concise demos and explains them really well. (Though I think it would take someone without existing familiarity with the subject matter a lot longer than 10 minutes to digest the results. Lots of rewatching!) A really interesting results that's come out of Matthias and co.'s research in the last few years that is still percolating its way through the real…
This is very coincidental timing. The physics simulation in the Source game engine, and Garry's mod, absolutely cemented in me an interest in computational physics. I really wanted to see fully simulated fluid water in games, particularly GMod, but it never really happened, 15 years ago. This never stopped bothering me, so I recently loaded up the game and programmed an entity that was simply a particle that repelled…
Realtime fluid sim is making lots of progress, though full 3D sims still appear to be computationally out of reach, at least for games that aren't focused exclusively on them. Here are some fun fluid sim examples from members of the Ten Minute Physics discord:
https://twitter.com/Michael_Moroz_/status/159507609967093350...
Re: Ten Minute Physics
#15Ten Minute Physics is a great resource! Matthias Mueller makes concise demos and explains them really well. (Though I think it would take someone without existing familiarity with the subject matter a lot longer than 10 minutes to digest the results. Lots of rewatching!) A really interesting results that's come out of Matthias and co.'s research in the last few years that is still percolating its way through the real…
This is very coincidental timing. The physics simulation in the Source game engine, and Garry's mod, absolutely cemented in me an interest in computational physics. I really wanted to see fully simulated fluid water in games, particularly GMod, but it never really happened, 15 years ago. This never stopped bothering me, so I recently loaded up the game and programmed an entity that was simply a particle that repelled…
The problem sounds like you're doing O(N^2) calculations at every tick because each particle has to interact with every other particle. To make it faster you should keep some spatial datastructure so that you can query the other particles within a certain range of your current particle and just interact with those, ignoring the rest.
The usual implementation is an octree or something similar.
That said, N=100 should still be fast with the naive algorithm so I'd definitely move off the scripting language to something faster.
Re: Ten Minute Physics
#16This has one of thoe timeless qualities to it. Reminds me of the old NeHe opengl tutorials.
Re: Ten Minute Physics
#17This has one of thoe timeless qualities to it. Reminds me of the old NeHe opengl tutorials.
"NeHe opengl tutorials" - these words of wisdom trully brings me back in time.
Re: Ten Minute Physics
#18Ten Minute Physics is a great resource! Matthias Mueller makes concise demos and explains them really well. (Though I think it would take someone without existing familiarity with the subject matter a lot longer than 10 minutes to digest the results. Lots of rewatching!) A really interesting results that's come out of Matthias and co.'s research in the last few years that is still percolating its way through the real…
This is very coincidental timing. The physics simulation in the Source game engine, and Garry's mod, absolutely cemented in me an interest in computational physics. I really wanted to see fully simulated fluid water in games, particularly GMod, but it never really happened, 15 years ago. This never stopped bothering me, so I recently loaded up the game and programmed an entity that was simply a particle that repelled…
> At this point, there are now other non-CPU bottlenecks. Any method of drawing 700 entities, even basic wireframe?, even with a very high end GPU on a nearly 20 year old game, is significant, and there's no easy way for me to break past this.
I've run into this before - it _can_ be fast if your engine supports some form of mesh instances and exposes it to the user.
Re: Ten Minute Physics
#19Earlier quoted context omitted.
This is very coincidental timing. The physics simulation in the Source game engine, and Garry's mod, absolutely cemented in me an interest in computational physics. I really wanted to see fully simulated fluid water in games, particularly GMod, but it never really happened, 15 years ago. This never stopped bothering me, so I recently loaded up the game and programmed an entity that was simply a particle that repelled…
Realtime fluid sim is making lots of progress, though full 3D sims still appear to be computationally out of reach, at least for games that aren't focused exclusively on them. Here are some fun fluid sim examples from members of the Ten Minute Physics discord: https://twitter.com/Michael_Moroz_/status/159507609967093350... https://twitter.com/MytinoGames/status/1600278137564184579
I might have to join the discord, that first link is extremely satisfying, and the shading on the materials in the 2nd one does a great of giving the feeling of the 3rd dimension without the computational complexity. Thank you for sharing
Re: Ten Minute Physics
#20Didn't realise at first that some of the demos were interactive, e.g. the cloth can be pushed around with the mouse. Impressive!