Erik Hofman wrote:

Drew wrote:

Hey All,

I'm running flightgear on Windows, and have noticed that it seems to
use up all of the available processing time, and because of this, it
seems to get jumpy when other applications are being used while
FlightGear is running.  I noticed that I can try to bump up the
priority of FlightGear, and everything else comes to a complete halt.

I did experience that running Acrobat Reader and FlightGEar simultaneously does cause this behavior. To my opinion there is just one thing that can cause this, another application is also using OpenGL (or DirectX?) for it's rendering...

This is done more and more to get hardware support for screen rendering. You might want to experiment a bit to see which program that might be.

I don't mean to get into OS advocacy here, but it's been my observation that Windows runs single monolithic apps as good as any OS available. But when you want to run a lot of little apps, it's process management isn't as refined as unix, and apps quickly become less responsive than you like. Similar issue with files. Windows can handle big large files pretty much as well as the next OS, but when you start dealing with a lot of little files, the performance of it's file system starts breaking down. I know there are many more details underlying all this and I'm sure we could all swap stories about how our favorite OS outperforms the competition under some particular circumstance, but let's not. :-)

Having said that, the operating system can't work magic. If you only have one CPU, it's going to have to be shared between all the things you need to run. If you run other applications, they will steal CPU time away from FlightGear making it jumpy. Unix has some nice process management features that can often hide these effect when additional lightweight apps are run, but again, it can't work magic.

Also look at your disk activity. IDE drives require a lot of help from the CPU to do the reads/writes so if your other apps are loading or writing files and your disk subsystem is IDE, that can really kill your performance, and the OS can't help there. SCSI drives and controllers are a lot more expensive, but they can do DMA block transfers without involving the CPU so you can do a lot of disk IO and run a CPU intensive app at the same time without them stepping too much on each other.

Just bear in mind that you are sharing resources if you are running multiple programs on your computer. FlightGear typically needs *all* the resources for smooth rendering, so running additional apps can cause jitters.

Here's another tip ... enable sync to vblanc ... that will help stabalize your frame rate quite a bit and automatically throttle's flightgear to your monitor's refresh rate. I often tune down my monitor to refresh at 60hz (even though it can do higher) so that I can get a nice sync/frame rate with FG. When you sync to the vertical refresh signal of your monitor, and when you can sustain that rate, you get incredible silky smooth animation with FlightGear and it's a beautiful sight to behold!



Curtis Olson HumanFIRST Program
FlightGear Project
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