Sam Varner writes:
>
>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.
>
>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.

Cool  - get it running first as they say :-)

>> Main / Location.hxx is a good place to start looking but my
>> question is what does your 'cartesian vector' represent ?

>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?

My guess is the scenery_center and update everything to reflect
this when this changes.  I think that we can just borrow code from
'prep_ssg_node'  in svenery / tile_entry.cxx to handle this when that 
need arises

>> 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?

from the ellipsoid's < sea-level > surface

The normal reported by the scenery class 
is the normal to the terrain at this point. 

Clear as mud,  right :-)

Cheers

Norman

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