On Wed, 2002-06-05 at 14:15, Christian Mayer wrote: > Tony Peden wrote: > > > > > PS: As the air pressure curve is similar to the > > > e-function (e^altitude) > > > it's nowhere linear and thus badly approximated by a > > > table... > > > > Depends on how many points are in the table. > > Yes. You can solve all problems with raw iron... > > I don't know how feelable the sudden performance drops are when you > arrive in a new part of the table...
There's two ways to implement the model with tables. One is the brute force approach that LaRCsim uses. It maintains a tables of T,p, and rho as a function of altitude and interpolates as needed. The second comes up when you implement the model as specified by ICAO, that uses a table of constants that get plugged into one of two equations (depending on whether or not the region is isothermal). JSBSim uses the latter. The first will require a lookup and interpolation every frame its executed while the second may not require a lookup (the table only has eight breakpoints even if it does) and will incur the cost of evaluating the equations (they are e^x, I've no idea how much FPU/CPU time they incur). I don't really know, but I'd guess it's a toss up. > > CU, > Christian > > > -- > The idea is to die young as late as possible. -- Ashley Montague > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
