On Fri, 26 Apr 2002 09:33:00 -0500 (CDT) "Curtis L. Olson" <[EMAIL PROTECTED]> wrote:
>Ok, now isn't this very interesting. There is definitely some >confusion going on here. I agree with Jim, it's not the fault of the >viewer code. > >Ignoring the issue of the CG possibly moving during the simulation, >the assumption has always been that the FDM returns the position and >elevation of the CG of the vehicle. The viewer (for better or worse) >has always drawn the view point relative to the CG of the vehicle. > >Now we have the ability to offset the pilot view point relative to the >CG of the aircraft and have been doing that, but I'm not sure how that >is now being handled in light of the recent view manager overhaul. >I'm not sure where the code now resides, and I'm not sure where the >pilot view point offset is now configured. Jim can probably speak to >that. Well, I'm glad to hear (for once? :-) that this does not appear to be a bug with our (JSBSim) stuff. I remember paying lots of attention to this kind of thing when initially doing the landing gear model and I don't want to go through that again any time soon. Thanks to Curt for looking through this so thoroughly. I have a couple of comments: 1) We actually always return the altitude that the always-working radar altimeter reports. For JSBSim model aircraft, the radar altimeter is ALWAYS at the current CG. :-) So, we simply report the CG position. 2) ACHTUNG!! The CG location can change, and when the multi- capability within JSBSim is done we will be able to drop bombs and the CG will shift abruptly. There's also fuel burnoff that shifts the CG. We provide the pilot CG in JSBSim config files in structural coordinates. I can't remember what was decided this provided value would be used for, but IIRC JSBSim developers would like the provided value to at least be used as an initial location or as a strong recommendation. Remember that the pilot position is important to us because we add ballast for that location and because pilot accelerations are figured for that location. Anyhow, even if the CG shifts, the pilot viewpoint would NOT shift in the structural coordinate frame in which it is defined. However, it will shift its relative position to a "floating" CG location. Jon _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
