Jon Berndt writes:
> >
> Could this be solved if the "camera viewpoint" looked at the CG instead of
> the VRP? What is being done, now?
The camera viewpoint need not necessarily be either or any fixed point
i.e. the camera should be free to look around :-)
What is required is that the 'center of rotation' of the aircraft is
about the proper point.
> > But since this is an abstract thing it is good to have a 'public'
> > thrashing so all can gain an understanding of the issues involved
> > please note this is non-trivial to most and not just a simple
> > feature request which has far reaching consequences on the very
> > 'core' of most everything within the SIM
>
> Definitely.
>
> > so to outline what I have gleaned so far
> >
> > 1) the 'modellers' coordinate frame will be
> > [ X ] longitudinal increasing aft < i.e. > smallest at the nose
> > [ Y ] latitudinal increasing right < i.e. > smallest
> > at the left wing tip
> > [ Z ] vertical increasing up < i.e. > smallest
> > at the ground
>
> This is definitely my strong preference, but can even this be adusted with
> the offsets?
Yes this could be adjusted, probably easiest todo with a single matrix,
as is done with the conversion between SSG space and OpenGL space
ie in SSG space X is to the right, Y is away from the viewer, Z is up
and in OpenGL X is to right, Y is up, and Z is into the screen
and is conversion is accomplished by inserting the
sgMat4 _ssgOpenGLAxisSwapMatrix =
{
{ 1.0f, 0.0f, 0.0f, 0.0f },
{ 0.0f, 0.0f, -1.0f, 0.0f },
{ 0.0f, 1.0f, 0.0f, 0.0f },
{ 0.0f, 0.0f, 0.0f, 1.0f }
} ;
into the viewer pipeline, but do we want or need this extra flexibility
I think it best if we all just agree that this is the coordinate system
that will be used :-)
> > 2) within this frame a VRP < virtual refrence point > will be designated
> > to represent the origin of the coordinate frame with respect to the
> > 'tip' of the nose of the aircraft.
>
> The VRP represents the location that the FDM reports the lat/lon/alt of,
> since it is a comprehensible (by all parties) fixed point.
It was my understanding that the VRP was decided by the modeller,
most often for ease of 'modelling' and not for any 'physically based'
reasons. IMO we want a 'consistant' position on the frame to be the
reported [ lat, lon, alt ] location. I would argue that the position returned
by Object.getBsphere->getCenter() is the 'logical' choice for this as
it will make other parts of the SIM easier < read more direct > to keep in
sync, of course any location shift can be compensated for.
> The rendering code is beyond me ...
The rendering code is no different WRT to the 'meaning' of the
various 'reference' points then the code the FDM needs to use
to place the objects appropriately into the 'world' with the added
complexity of merging the coordinate frames.
Cheers
Norman
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