On Fri, 9 Nov 2012 20:37:10 +0000, Stuart wrote in message <CAP3ntysv=1xcks8nk_ssk3+e8-wwrbmwulwomaquy3vy0gd...@mail.gmail.com>:
> On Mon, Sep 10, 2012 at 12:26 PM, Jan Comans wrote: > >> We should have a random number generator in simgear that returns > >> the same random number within the same period of time (I believe > >> it was set to 1 second) to prevent short time quirks between > >> different machines. This was specially added for (random) clouds. > > > > I have looked at this, but as far as I can see FG calls the regular > > time seed intialization instead of the 'time period' one. I think > > the period is even 10min. But I recall having some issues with > > giving the whole simulation a fixed seed (either through the > > srand10 method or providing a custom seed). Next to that, the time > > period seed relies on the fact that system clocks are more or less > > in sync. Normally NTP should take care of that, but with our sim > > being tweaked constantly this is difficult to guarantee. This for > > me is also a reason for providing a separate rng to handle the part > > that I'm interested in. As I said before, form me this was just a > > quick and dirty hack to get the results we needed. Personally, I > > think it would be beneficial to put the randomness somewhere in the > > property tree so that the cloud code can build 'deterministic' > > clouds from these values. In this way, other FG instances could be > > coupled in way similar to using --fdm=external, and just receive > > the basic random seeds that would result in the same cloud fields > > on every instance. But that's just my idea without having looked at > > the code too much. > > I've committed a change to keep the clouds in sync across > multi-process systems. > > It relies on the clocks of the systems being roughly in sync as the > seed changes every 10 minutes. ..are we now close to be able to run a FlightGear clock service, e.g. over a multiplayer network, independently from real time or hardware clocks, to e.g. render a 4K cinematic quality movie at say 4% of real time speeds 'n framerates? -- ..med vennlig hilsen = with Kind Regards from Arnt Karlsen ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_nov _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
