--- Norman Vine <[EMAIL PROTECTED]> wrote: > Jon Berndt writes: > >> > > We all know that we can rotate the 3D model correctly, but the > issue is > > the translation. JSBSim reports the location of the CG, which is > NOT the > > translation for any point on the aircraft, but ONLY the CG. > > > > So, the solution is that JSBSim (and other FDMs) could report the > location > > of the 3D model origin at every frame for rendering purposes. OR, > > FlightGear could derive it - given it may have more intimate > knowledge of > > the 3D model AND the CG. True? Problem is, the FDM guys don't KNOW > what > > point will be chosen for the 3D model origin. The FDM could report > the > > position of any point in our own coordinate system. If we gave the > > location of the nose as a commonly known reference point, then I > believe > > the rendering code could have that location to use as its "pivot > point". > > > > I hope I understand the problem correctly, and that this isn't > muddying > > the water. > > I think that when we add colision detection into the mix the most > sensible reference point is the center of the bounding volume > > collision includes wheel-runway contact points ect > > we used the static center as a 'close enough kludge' historically > but if we are going to change the location IMHO we should do so > in a way that increases accuracy. ie the nose is further away from > the geometric center then the published static center
The point we pick need not have any particular signifigance (we can calculate a lat/lon/alt for anyplace relative to the aircraft), so why should we pick a point which requires explanation and/or instruction on our part and more work on the part of the 3D modeler. The nose is something that everyone can instantly understand and locate. That is not true for the aero ref point, center of gravity, center of geometry, etc. FWIW, I still think the location should be configurable by the 3D modeler in the FG xml files. FG would pass that info to the FDM and it would return the appropriate position or FG would do the calcs itself. The wind doesn't seem to be blowing that way, however ... > > So to summarize the needed locations discussed so far > > 1:center of gravity > used by FDM > 2) aerodynamic center > used by FDM > 3) eye location > used to render the scene > 4) geometric center > used by SSG and collision detection > > Of these the one that corresponds to 'everday speak' > and common engineering usage is (4) Well, now, that depends on what kind of engineering you do. > > Norman > > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
