I'm looking for a fixed-point 3D physics engine (basic kynematics and collision detection-resolution... nothing too fancy.)

I need fixed-point math because I'd like to have deterministic results, for reproducibility purposes, and high portability, because I expect my game to be highly portable for devices such as mobile phones or portable gaming consoles without floating point units.

  • \$\begingroup\$ The only physics engines I know that support fixed-point math are 2D ones. I get your desire for determinism, because that's nice to have, but is it actually a requirement? And there are many portable physics engines, fixed or floating point doesn't have a whole lot to do with that unless you need them to run in lockstep across platforms or something similar -- do you? \$\endgroup\$
    – user1430
    Feb 16, 2011 at 16:17
  • 2
    \$\begingroup\$ It's a requirement, since this is planned for a networked turn-based game where each player shared their orders with other players at the end of each turn, and they simulate the result, which has to be the same, exactly, and no authoritative server can be in the middle (p2p game.) I intend it to be portable, not only between OSes, but machines too, even ones without FPU like NintendoDS. FPU results may even be unconsistent between different compilers in the same OS, so think about different architectures... \$\endgroup\$
    – kaoD
    Feb 16, 2011 at 16:19
  • \$\begingroup\$ Did you find a fixed-point 3D physics engine yet? I'm looking for one too. \$\endgroup\$
    – Ergwun
    Apr 20, 2011 at 2:56
  • \$\begingroup\$ @Ergwun nope I didn't... I guess they just don't exist. \$\endgroup\$
    – kaoD
    May 7, 2011 at 19:46
  • \$\begingroup\$ Yeah, I've given up looking too. \$\endgroup\$
    – Ergwun
    May 9, 2011 at 1:55

1 Answer 1


You can try asking guy who made tutorials on Flipcode on 3d fixed point math on mobile devices, he made games and they included physics.

(Some old games used fixed point (guessing Carmageddon, Destruction Derby ...). Fixed point is used on some mobile devices and they have games, and some of them are 3D.)

I hope it helps. :)

  • \$\begingroup\$ Not exactly what I was looking for, but nice information. I didn't explore the AirplaySDK too much nor did I see any license, but it looks like it's propietary software. I will end up coding my own physics engine (or at least a fixed-point math replacement) so the first like would be a great starting point. \$\endgroup\$
    – kaoD
    Jun 15, 2011 at 19:27
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    \$\begingroup\$ @kaoD Some more about fixed point physics I found by googling. I was wondering if such stuff is possible in Bullet and it seems some guys tried it. I believe Bullet is good, so this is natural to search for it there ... Contact them or google more for (ODE fixed point, bullet physics fixed point, ...) \$\endgroup\$
    – user712092
    Sep 8, 2011 at 8:38

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