On Wed, 3 Apr 2002 16:26:57 -0600 (CST) "Curtis L. Olson" <[EMAIL PROTECTED]> wrote:
>The FDM defines some aribitrary reference point (i.e. on the firewall) >and provides the lon/lat/elev of that point. We provide the lat/lon/elev of the current _CG_. >The FDM really doesn't care about the actual FlightGear view point. True. >It won't know if the user is flying from the left seat, the right >seat, or seat 5A in the DC-3. True. >It seems like it would make much more sense for the flightgear side >(maybe the aircraft-set.xml file?) to provide the actual view offset >point relative to the FDM reference point. All true. I just want to make these points: 1) In JSBSim (and I am assuming in YASim, too) one can add a weight to where the pilot sits - or anybody for that matter, including someone seated in 5A or a piece of luggage, etc. This will typically be where the pilot sits. If you change the viewpoint you won't be changing where the "pilot ballast" is. You'll merely be changing the viewpoint. You won't be virtually walking around the aircraft. 2) The flight modeler will usually have an intimate knowledge of where the *pilot* sits from aircraft manufacturer 3-views or other means. In some cases this data is given directly as X, Y, Z coords in the structural frame. An aircraft 3D modeler might have this information, too, if working from the same diagrams, or [s]he can probably guess fairly well. 3) The turn coordinator instrument (to my knowledge) works in consideration of where it is located, typically right in front of the pilot. The accels sensed by this instrument include rotational effects at the pilots moment arm from the CG. 4) If FlightGear was ever to be hooked up to a motion base, the motion of the base might be linked to the second derivative of the body velocities _at_the_pilot_location_. Thus, again in this case and with point #3, above, the flight model still needs to know where the pilot is. I still recommend that the FDM be allowed to at least _recommend_ a pilot eyepoint, as some calculations inside the FDMs will use this value. It would be nice if this value could be useful to FlightGear. FlightGear could still be allowed to shift the viewpoint as it wished, but withe understanding of points 1 - 4, above. Jon _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
