Jim Wilson wrote:
 > Andy Ross wrote:
 > > David Megginson wrote:
 > > > Something is overwriting the xyz offsets in the c172-3d-set.xml or
 > > > maybe it isn't reading that file?  Those are defaults from
 > > > somewhere...probably from c172-set.xml.
 > >
 > > YASim _sets_ those offsets based on its own configuration.  I think
 > > this is a problem of data ownership -- who "owns" the location of
 > > the cockpit?  I argue that it's the FDM, since it's the code
 > > responsible
 > That isn't the issue here though.  Those are just the offsets from the
 > lon+lat+alt to the eyepoint and it was those that were off.  Where
 > that origin is FDMwise is another issue and not related to what David
 > was observing.

No, I meant the airframe offsets, not the global ones.  The following
code appears in YASim.cxx (the negations are due to the difference in
coordinate sense):

     // The pilot's eyepoint
     float pilot[3];
     fgSetFloat("/sim/view/pilot/x-offset-m", -pilot[0]);
     fgSetFloat("/sim/view/pilot/y-offset-m", -pilot[1]);
     fgSetFloat("/sim/view/pilot/z-offset-m", pilot[2]);

Ultimate, the pilot position comes from the <cockpit> tag in the YASim
.xml file.  The rationale here was that this was the best place to put
the information about the cockpit position was in the aircraft
definition.  But that was before the 3D model work got done.  Now,
there are *two* aircraft definitions: one to decide on physical
performance and one to control visual display.  Basically, we need to
pick one mechanism.  I think the simplest thing to do would be to yank
the YASim <cockpit> mechanism (and whatever JSB and UIUC do) and use
the model stuff only.  Then, at least, we're guaranteed to be
consistent across FDMs so long as we get the origin correct.

The axis mixup, though, still requires a solution.  My guess is that
the new viewer draws the new models correctly in their (new)
coordinate system, but misinterprets the offset information generated
by the FDMs.


Andrew J. Ross                NextBus Information Systems
Senior Software Engineer      Emeryville, CA
[EMAIL PROTECTED]              http://www.nextbus.com
"Men go crazy in conflagrations.  They only get better one by one."
  - Sting (misquoted)

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