Jon Berndt <[EMAIL PROTECTED]> said: > I have seen posts to the effect that there IS a problem with properly > communicating the origin, and that this problem deals with rotating the 3D > model as specified by the FDM Euler angles, but NOT accounting for the > fact that the FDM assumes rotation about the CG, and the 3D model rotates > about a different point, such that the CG moves improperly and perhaps > puts the gear underground or something. Is this correct?
Jon, Thought I should go back to this question to clarify why I don't see a problem. A couple of geometric assumptions: 1) Roll, Pitch, and Heading are always the same for every position on the aircraft. It'll be the same at the variable CG as it is at a fixed point on the nose. 2) The position of the aircraft is always reported at the same location. In otherwords Lon/Lat/Alt is always reported from a fixed location on the airframe. If those two are true then there should never be a problem. The primarily effect of longitudinal CG movement will be on the reported Alt (Altitude) of the aircraft. For example if the CG moves toward the back and the Altitude is reported at the nose of the aircraft, then one degree of pitch change will have a greater effect on the change of altitude at the nose. Movement of the CG will also affect the reported lon/lat of the aircraft, including lateral movement. So all we need to do is rotate the 3D model at the same location as the lon/lat/alt is reported and we should be reasonably correct. Close enough to be visually correct. This could be a good argument for reporting position data at the nose, far away from CG: Greater precision for reflecting the CG variation effect. Best, Jim _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
