On Fri, 2002-03-15 at 14:51, Andy Ross wrote: > Tony Peden wrote: > > Andy Ross wrote: > > > You give the scenery the position of the gear min/max comprssion > > > points, and it tells you where the tip really is. > > > > That is, IMO, precisely the job of the gear model. Only the gear > > model can and should "know" the path that the wheel follows as it > > compresses. I'll certainly agree that right now it's not necessary to > > model anything more than compression along a straight line, but we > > know that's not real in alot of cases and should allow for it in the > > design of the FG-FDM interface. > > I don't necessarily disagree,
But by asking the scenery code to do the intersection for you, that's exaclty what you are doing, AFAICT. > but I'm at a loss for how you get this > effect by assuming that gear compression is always along a line normal > to the ground plane? I wouldn't make this argument, I'd say it's reasonable to assume *body* axis z compression only (though you shouldn't lock yourself into that, there are many examples where that's not the case, the F-18 and Cessna 172 being two), a very different thing. > > If anything, this would argue for an interface more like mine, where > the FDM can "probe" the scenery for intersection points rather than > blindly trust an "elevation" number for each gear and assume a flat > ground plane under the gear. Why would this entail the assumption of a flat plane? We ask for the compression under (or, conversely, the agl altitude) of each contact point and whatever it is, it is. Whether the ground has a simple slope or undulates within the area formed by the gear contact points, it doesn't matter. Even a nicely non-linear curve like a ski-jump is not a problem. All we care about is the agl height of each wheel (and in particular whether its negative or not), not what may be happening in between. > > > A significant benefit will be had immediately -- the aircraft will > > follow the terrain while taxiing and the 3D model will look better. > > If you mean the aircraft will be tilted on non-level ground, then you > can get that effect already by inspecting the normal vector. When I > say "flat", I don't mean "level". Take a look at the YASim code > (which supports, but does not use, a terrain normal vector) for an > example. Sure, but we can get that and a ski-jump capability knowing the agl altitude of each wheel. > > I'm not quite sure what you mean by the 3D model. Assuming vertical > gear compression is no closer to rendered reality than what we are > doing now. You'll get a tilt, but not a physically correct one. > > Andy > > -- > Andrew J. Ross NextBus Information Systems > Senior Software Engineer Emeryville, CA > [EMAIL PROTECTED] http://www.nextbus.com > "Men go crazy in conflagrations. They only get better one by one." > - Sting (misquoted) > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
