On Fri, 15 Mar 2002 15:29:05 -0800 Andy Ross <[EMAIL PROTECTED]> wrote: >We either have to have scenery code that understands funny gear >trajectories or gear code that understands 3D collision >detection.
We can be fairly simple. If you want to do articulated F-18 gear, be my guest. All I want to know is what is the darned elevation at a given lat/lon, and eventually perhaps the roughness, the "bouyancy", and the surface normal. > >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. > >Bingo, here is the disconnect. The current terrain intersection code >gives you an altitude above the ground plane for each gear. That >allows only for compression along the ground's "up" axis, not the >body's. This is, in fact, what the JSBSim gear code uses. We do compression only along the vertical axis (the ground Z axis). As I keep repeating to you - even at an angle of up to 20 degrees, the *compression* "error" maxes out at several percent (less than 7). The runway exerts a force on the aircraft in the RUNWAY vertical direction (in real life, of course, this would be more accurately a runway _normal_ direction). It would be no big deal to compress the gear along its own body axis (for a non-articulated single strut), but we have more pressing things we are working on than doing ski jumps with airplanes at present. Providing the elevation at a single lat/lon gives _us_ a nice feature. If you don't want to use it, you don't have to. >I completely agree, by the way, that assuming the body frame >compression is always along the Z axis makes sense. In fact, while >YASim in principle supports any gear compression axis, I only bothered >supporting Z axis compression in the parser. > >I guess I'm just a little flummoxed at the resistance to >doing things "right" here. I mean, it doesn't take any more CPU time; >it doesn't make the FDM's job any more complicated, and it's >reasonably well-supported by the scenery code as-is. All that's >needed is an interface change and we're done. Maybe you need to re-state what you are thinking is "right". Something's not getting communicated. Jon _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
