On Thu, 2002-05-02 at 20:14, Jim Wilson wrote: > Sam Varner <[EMAIL PROTECTED]> said: > > > I want to get the elevation of the ground for points other than my > > current location. I suppose I could do this by moving to a new location > > and calling scenery.get_cur_elev(). Is there a better way? If not, > > what operations will update the output of FGScenery::get_cur_elev() in > > the most efficient way? > > > > That's actually a problem that I'm working on currently. If you look at > tilemgr.cxx, the update() function you'll see where the value for current > elevation gets set. What you can do is modify that function to accept an > "absolute view position" vector along with the longitude and latitude > paramters and pass it along to the hitlist fgCurrentElev call. > > Take a look at "location.cxx" to see how that "absolute position" vector is > calculated (it is actually based on the latitude and longitude with the > altitude integraded to give you coordinates in 3D space). Calling the > update() routine in this way causes some trouble with the tile caching because > the caching is based on distance from the longitude and latitude you specify. > > When the routine was written we were dealing with a single view location and > an a longitude and latitude that changed gradually, not abruptly. If you keep > jumping that around the tile cache starts thrashing a bit (unless the > locations are reasonably close to each other). All this said, calling > update() will give you the readings you are looking for. Just make sure that > the current elevation gets set right back to whatever is correct for the > aircraft (the value returned by scenery->get_cur_elev()), otherwise you'll see > some other issues come up. > > Sometime in the next week or so look for updates to this code that will make > what you want to do a little easier and fix the numerous bugs in the scenery > and sky rendering that have come up since the new viewer code was introduced.
I'll be more explicit about what I'm trying to do, and you can tell me if you want to change your answer:) I'm working on a car model; the elevations I want are the elevations under each tire. The points will be close together, so there shouldn't be any tile cache probelms, but I'll have to do the calculation for each tire (and any other point on the car that could come into contact with the ground) every time step. Also, I don't want the point-of-view to change as I'm checking each potential contact point. Is update() still the way to go? Thanks. _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
