> 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. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
