On Thu, Nov 8, 2012 at 11:12 PM, John wrote: > Yes, your are correct it you run a single instance of fg with three > displays with whichever scheme you use; e.g. using the XML file to create a > left, center, and right camera for the scene or one of the video splitters > to break a single large camera into three channels for each display. > > However, if you run an instance of fg using, for example, the center as the > master FDM, then create two "slave" fg's using the FDM=NULL option for each > left and right instance each instance starts with a different random seed. > This occurs whether you run all three instances on a single CPU or, as in > our case, each instance on a single core of a multi-core machine since each > instance creates it's own scene graph. The advantage of the multi-core > machine is performance limited only by the bandwidth of the busses and > graphics pipelines and GPUs. have not really drilled down just where or > what are the limiting factors using a multi-core machine with multiple video > cards; just know it is faster based on fps for each core versus running > everything on a single core machine. The disadvantage is many of the > dynamic features like clouds, AI traffic, etc are not sync'd across > processes. > > Jan Comans solved the problem by using a *fixed* random seed ( another > oxymoron ;-) ) for the 3d clouds at least.
As mentioned elsewhere, I've just committed a time-based random seed for cloud generation to fix this in origin/next. Please let me know how you get on. On Fri, Nov 9, 2012 at 8:08 PM, Torsten Dreyer wrote: > just one more note about multi-displays on a single machine: With our > four cards driving eight displays at 1600x1200, the 3d clouds appear > seamless across the individual displays and they work fine when clouds > are scattered or few and you stay well clear of the clouds. When a cloud > starts occupying a big part of one or more screens, there is a massive > drop in frame rate, down to unusability. > The same hardware runs smooth with 60fps (synced to vblank) in any > situation with just a single display. I think that's just a side-effect of having so many pixels covered by (multiple) quads with alpha. I'm not sure there's much we can do about that, unless we somehow start dropping sprites. I'll have a think - 3D cloud perf has always been a big challenge. -Stuart ------------------------------------------------------------------------------ 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
