Craig Pepper (craigp++at++matra.com.au)
Tue, 09 Feb 1999 08:14:36
Well, not neccessarily. It seems to me that choice of coordinate system
axes is just a convention (compare OpenGL Y up, Performer Z up, and the Z
down system used by our aero guys). Choosing different axis directions
depending on the hemisphere you're in would be a pain to implement and
fairly inefficient. Either that or you'd fall out of the sky as you passed
over the equator (and it's not even the year 2000 yet :-).
We've implemented a double precision spheroid (lat, long, altitude)
coordinate system that resolves to a right-handed float coordinate system
around an origin tangential to the spheroid, with +Z up, +X east and +Y
north. This fits in with pf coordinates and works fine all over the globe,
and note that we do most of our flying in the southern/western hemisphere.
Our coordinate system does have to reverse the sign of compass headings (0
north, increasing clockwise) to make them pf friendly (0 +Y, increasing
counterclockwise).
Just hoping to head off any confusion that might result from the previous
post.
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Craig Pepper Home: craigp++at++matra.com.au Work: cpepper++at++syd.csa.com.au
Visual Simulation Development
CSC Australia Pty Ltd
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