Re: [Flightgear-devel] JSBSIm and altitude-agl-ft

[Adams.syd <ada...@gm...>]

I can also confirm this.same thing happens flying from Cyvr to cyyj.i get stuck in midair about halfway there,over the ocean.

Sent from Samsung Mobile

 Renk Thorsten <tho...@jy...> wrote: 



We have an odd bug with JSBSim planes hitting something solid in mid-air:

http://forum.flightgear.org/viewtopic.php?f=25&t=22743

The test case is to take off from EGFF (Cardiff) on runway 12, climb and maintain 120 degrees. Off the coast, there is a 'wall' in the sea where the ocean landclass of the coastal tile meets the generic auto-generated ocean landclass and they have a mismatch of a few meters in altitude. Since we're probably not bothering with z-buffer filling when rendering ocean, this also shows as a rendering artefact when seen from the right angle.

Crossing this line, position/altitude-agl-ft goes to zero in JSBSim planes (apparently not for others). This in turn seems to trigger ground interaction code, crash detection etc. where this is implemented, leading to unwanted side-effects.

Other users have reported that JSBSim also returns altitude-agl-ft of zero when the plane is above a gap in the scenery (no landclass defined, experimental terrain, possibly no tile loaded due to a hung tile manager...). It may be that this is a bug we've been carrying for a long time, but without ground interaction code and crash detection, it never became much apparent.

So it would seem that discontinuities in the terrain mesh trigger something in JSBSim that confused the altitude above ground determination. If the JSBSim knowledgeable people could perhaps take a look?

* Thorsten
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