On Wed, 2002-04-17 at 18:47, Norman Vine wrote:
> Eventually anything displayed by SSG, the SceneGraph component
> of PLib, has its orientation specified by a rotation matrix.
> 
> So it may be you do not need to go from Matrix to Euler Angles and
> back again to a Matrix.  My guess is that your orientation is with
> respect to the local tangent plane and this may in fact be good
> enough as is, if not it certainl;y is no more then a Matrix multiply away
> :-)

If someone shows me how to use my matrix directly, I'll do that.  For
now I've written a conversion function that I'll probably stick into my
matrix class.

> Main / Location.hxx is a good place to start looking but my
> question is what does your 'cartesian vector' represent ?
> It could well be that there is a 'short cut' you can take
> as geocentric coordinates are also a 'cartesian vector'.

The position vector points from some anonymous origin to the origin of
the vehicle's frame.  The origin is wherever the vehicle would be if you
didn't move it.  You could put the origin wherever you want by
explicitly setting the position vector, as long as you do the correct
transformation to FlightGear's coordinate system.  What origin makes the
most sense in this context?

> Note that I may be a little vague as to exactly what Matrix
> you want to use to transform your vectors in that others
> are restructuring the pipeline but I believe that the one you
> are probably most interested in is still called UP

I'll give it a try.

> This represents the surface normal's orientation matrix
> at the current location

Is this normal to the sea-level surface or normal to the terrain?

Thanks for your help.  I'm getting close.


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