On Sunday, June 22, 2003, at 01:58 PM, Grant Hutchison wrote:
> BTW: It seems as if Celestia uses Radius as some sort of *maximum*
> radius
> when rendering 3ds models  is it the maximum radius overall, or the
> maximum
> radius in some defined plane, or just the radius along a particular
> axis
> which turns out to be the long axis of most models?
I've been wondering about this issue myself, in connection with labels
for Eros. If I'm not mistaken, Celestia simply scales the model
coordinates by the radius value specified. In other words, if a point
in the model is at a distance 1.0 from the origin, it'll be scaled to
the distance specified by the radius value. So the result will depend
on how the model builder scaled the coordinates when creating the
model. I would guess that in most cases the model builder would scale
the model coordinates based on the point which is at a maximum distance
from the origin. But I could be wrong, and in any case there's no
guarantee, just as it's up to the model builder to get the center and
orientation correct.
BTW, 'solarsys.ssc' currently gives a Radius of 16.5 for Eros, whereas
the NEAR NLR190 shape model shows a maximum equatorial radius of
17.452, with a maximum chord of 32.687 (not in the equatorial plane).
 Hank
