Hi guys, (and gals if there are any),

I was inspired to make a ball simulation based on https://www.allegro.cc/forums/thread/617607, and I now have a fully functional if partially broken simulator.

It's pretty stable, but there must be some small condition I'm missing that allows balls to escape my 'pen'.

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As you can see, there are many balls with many different velocities and accelerations, and the intercept times are all calculated properly, except for every once in a while, a collision is failed to be detected. And a few balls still escape the pen.

Can anyone help me figure out what is going on?

I narrowed it down to this ;

1. An intercept is detected.
2. I advance time to the first intercept
3. At this point, the balls should touch, but not overlap (distance = 0)
4. Sometimes the ball overlaps
5. Time is advanced to the next intercept
6. Sometimes its so quick that the overlapping ball gets hit by another ball, driving it even further into the first ball. No collision can be detected because they already overlap.

In an attempt to remedy #4 I used the normal direction and "Pushed" the balls away from each other by half the difference between the distance and the total radial distance.

What can I do to prevent them from overlapping in the first place? "Rewind time" by a small amount so they never overlap in the first place?

I need to work on the numerical stability of the program as well, if anyone has any tips on that I would appreciate it.

I know I said never to move objects into overlap positions, but I'm not sure how to do that here. I feel like I'm going to have to 'cheat' somehow.

All the code is on Github here :

https://github.com/EdgarReynaldo/Merlin

That's amazing! How did you get them to stay put!

EDIT
What did you compile them with? What OS and architecture are you using?

Pull from git and try again. This time try with only 10-20 large balls (small balls can be launched with the RMB. The farther you are from the middle of the screen with the mouse, the faster they will go. Leave a little space.

I added a workspace project. I can add dynamic linking projects too if you want.

I just want to re-iterate that I freakin' love the "graph" like presentation. My brain is like "OOoooOOOhhh that could be a game."

I compiled it with gcc version 6.3.0 (MinGW.org GCC-6.3.0-1) on windows 7 x64 with latest allegro5 from git.

Got it fine too even with more than 450 little balls.

I have waited until there was no more overlapping, and none escaped.

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In which order do you do things ?
You have to generate new position, check if collide, then only if not swap old and new positions. If moving it make it collide it has to stay where it is and have its velocity/whateverelse reversed according to the bounce.
The best case would be to compute the intersect point of colliding, and then move accordingly to the first non colliding position, and reverse velocity/whateverelse according to the bounce.
So ?