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Howto:Troubleshooting Aircraft Performance Issues: Difference between revisions
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Howto:Troubleshooting Aircraft Performance Issues (view source)
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[[File:Su15-complexity-osg-stats.jpeg|right|thumb|http://forum.flightgear.org/viewtopic.php?f=4&t=25961&start=135]] | [[File:Su15-complexity-osg-stats.jpeg|right|thumb|http://forum.flightgear.org/viewtopic.php?f=4&t=25961&start=135]] | ||
== Objective == | == Objective == | ||
Document the main steps to understand performance issues at the aircraft level, i.e. FDM, 3D modeling, texturing and Nasal scripting. | Document the main steps to understand performance issues at the aircraft level, i.e. FDM, 3D modeling, texturing and Nasal scripting. | ||
{{FGCquote|1= you can use the osg-stats and use osgviewer/fgviewer in standalone mode to draw your own conclusions|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264190#p264190 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||
{{FGCquote|1= you can only draw reliable conclusions once you do multiple tests doing different settings/configurations, which includes all tools at your disposal - including different model viewers like osgviewer/fgviewer.|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264221#p264221 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||
{{FGCquote|1= in conjunction with viewing the model in osgviewer, fgviewer and fgfs using different settings, we can draw reliable conclusions.|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264221#p264221 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||
{{FGCquote|1= osgviewer is a good way to exclude FDM, Nasal and Canvas altogether - so it provides an excellent baselineAnd that is not specific to the Su15, you could just as well do the same tests with the 777 or the extra500, and anybody interested in understanding FG performance issues, is well-advised to use such tests to determine if, how and where certain features are contributing to those|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264221#p264221 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||
== Approach == | == Approach == | ||
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== Metrics == | == Metrics == | ||
The main metrics will be osg-stats (link) and frame rate/frame spacing when in FG, as well as ogging performance monitor metrics (link) | The main metrics will be osg-stats (link) and frame rate/frame spacing when in FG, as well as ogging performance monitor metrics (link) | ||
== Understanding framerate == | |||
{{FGCquote|1= What drags framerate is the number of model vertices in the view frustrum. When you don't look at the larger part of the cockpit because you're essentially looking out of the window with little of the plane in view, you get decent framerate. When you have the lower part of the cockpit and the forward part of the plane in view, you get lower framerate. When you have most of the model in view, you get lowest framerate.Doesn't really matter whether you actually see so much of the plane - vertices blocked by opaque surfaces still count in this game. Even if you see an instrument, the nose wheel a few meters before it will still kill your framerate even if you can't see it.|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=263133#p263133 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Thorsten</nowiki> | date = Nov 4th, 2015 }}}} | |||
== Use Cases == | == Use Cases == | ||
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== standalone FDM == | == standalone FDM == | ||
{{FGCquote|1= usually, the FDM accounts only for a fraction of the execution time over the overall time spent creating the frame, and given the complexity of the 3D model and textures, I would assume that quite some time is spent rendering, not updating FDM state. To see for yourself, you can open the performance-monitor, and post a screen shot here - next, do the same thing with the osg-on-screen stats.If in doubt, JSBSim also provides a way to run in standalone mode, you can basically run a 2 hr flight within a few minutes, and watch the whole thing using a task monitor (top/htop on Linux).This should tell you immediately if you are FDM-bound (which really is a fancy term for saying that you'd be CPU-bound), which seems unlikely as far as I can see.|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264210#p264210 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||
== osgviewer == | == osgviewer == | ||
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== Using draw masks == | == Using draw masks == | ||
{{FGCquote|1= people with very powerful hardware who are still getting only ~30 fps may want to hide the aircraft using /sim/rendering/draw-masks to see for themselves how much of an impact the 3D model/texturing vs. scenery/clouds etc has, note that this will not have any effect on running Nasal code|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=263960#p263960 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 11th, 2015 }}}} | |||
== Core Development == | |||
{{FGCquote|1= Those osg stats should really be dumped to the console during startup, maybe just the aircraft-specific branch, i.e. separated scenery/aircraft to write into the log file how complex an aircraft/airport (location) really is/was.I really believe that this is a useful metric, and the approach could also be suited to understand other issues, i.e. rendering a minimal view of a scene and removing/adding different elements using draw-mass to see if/how they impact overall scene complexity and performance.This would probably also help us understand Rembrandt issues, and it would allow us to identify opportunities for optimiing Canvas further - e.g. by allowing such stats to be gathered "per-canvas" (texture), querying the whole sub-graph for the corresponding cam, which is possible using existing osg APIs)In fact, aircraft/airport complexity I would even log to the splash screen right away, to provide some data to aircraft developers|2= {{cite web | url = http://forum.flightgear.org/viewtopic.php?p=264221#p264221 | title = <nowiki>Re: Su-15</nowiki> | author = <nowiki>Hooray</nowiki> | date = Nov 12th, 2015 }}}} | |||