>High!
>

>to get the ASCII matrix derived from a GeoTIFF parsed properly... but 
>now a new problem shows up: when I render the scene (code once again on 
>p.b.s-f), I get the warning message "Camera vectors are not 
>perpendicular. Making look_at the last statement may help."
>
>I did the latter, but nothing changed. How can it be that "camera 
>vectors are not perpendicular" - as I don't use up, right and direction, 
>only location, look_at and sky?
>
>The first picture is generated with 3DEM's 3D visualization module and 
>(roughly) shows how the scene should look like.
>
>The second picture is what I got instead...


One of your trace() rays doesn't intersect Earthslice. This leaves you
with "lo" being in the same direction as the sky vector, which produces
the error that you are seeing.

In fact, it's unlikely that your second trace() would intersect a
roughly spherical object, unless cNormVect and lNormVect are very
similar.

I suggest firstly:
  #declare la=trace(EarthSlice, lNormVect, -lNormVect);

Secondly, never assume that a trace() successfully intersects a surface,
get it to return the normal and check that it is not zero. Not just for
this scene, but as a general principle.


-- 
Mike Williams
Gentleman of Leisure

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