>[A bunch of notes on Norm's notes. Basically, everything he wrote > (even the editorializing) makes sense to me, with a few exceptions as > detailed below]
>Norman Vine wrote: > > Easy beans - no gimble lock - infinitely stackable orientations - > > everything has it's own logical spot - quick - elegant - natural > > orientation changes < ie slerp's > - the code is basically all in PLib > > for the using already - ect .... >Heh, you're a quat nut, huh? NO I HATE WORKING IN QUATS THEY MAKE MY HEAD SPIN :-) but they have their occasional place and this is one of them !!!!! > They're nice, but hardly necessary*. >The biggest difficulty is in picking the front-end interface, for > which quats basically suck. I want to have a hat switch mapping where >"left" becomes "subtract a little from view_offset". You can't expose > the quats to the user -- you need eulers for that, warts and all. There are euler to quat interface routines in PLib Use what ever interface you want but INTERNALLY I say you want quats when you are modeling a 'free' rotation otherwise you ALWAYS run into a 'singularity' that you CAN'T work around And of course there is the elegant way to control spherical accellerations that we haven't even talked about :-) ie I want my head a(de)ccelerating smoothly not with an unatural jerk > Now since every one seems confused a general overview of how FGFS > determines the 'VIEW' > > 1) the PLib coordinate system has the same 'sense' as OpenGL but is Z' > up. [...] this is a simple rotation of a right handed coordinate > system and is due to the fact that the PLib author primarily > writes FlightSimulators where this is a 'natural coordinate basis > If you don't like this fact either get over it or quit using PLib > Chill, Norm, we can deal. :) Hey all you had todo was ask and PLib has been that way from the beginning and we all thought every one just knew it :-) ie When in Rome do as the Romans ect.... > But having it spelled out somewhere more obvious would be nice. FWIW - I was not a big fan of adopting PLib for this and more importantly its NON-C++'ness but I accepted it and more importantly became a PLib developer jsut so I could watch out for FGFS Interests ! FYI - Several other FGFS'ers did the same feeling that developing PLib was developing FGFS. I feel sorry for all of those that think of PLib as an 'external' constraint it certainly didn't start off that way and it certainly needen't remain that way >I discovered it accidentally while browsing >through the source code. Just a hint for the next time you guys are >auditing the documentation. You mean you just ASSUMED we were using an OpenGL coordinate system ? > > 2) the LaRC coordinate system is different also but this should be > > handled transparently for you in existing code < see comment in > > viewer_rph.cxx > >There's a (reasonably) standard interface for the FDMs to export their >location and orientation. This bit isn't a problem. Hey LaRC Sim is what made FGFS possible and by default determined how a lot of things were done. FWIW this is a good piece of Quat code and is well documented in reference 1 at http://jsbsim.sourceforge.net/fsreference.html As Newton said 'I stand on the shoulders of giants' >This isn't quite fair. I wasn't party to the discussion, but the tilt >angle got added to solve a specific problem. The panel/UI world >*needs* an euler angle interface to the view direction to do its job. Bah It needs an interface . If you want to talk to that interface with eulers fine but it doesn't have to be an euler representation as you yourself just said it just needs an euler interface. >Under the existing implementation, the mouse code was the sole >aribiter of those numbers, didn't export them as anything but a full >quaternion, and didn't accept input from anywhere. So a new feature >was needed. Wrong the GUI exported an euler matrix ! From which you could have easily picked up the 'Mouse contribution' to the vies rotation with gram scmidt or whatever. OUT _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
