[daip] PROFL shadowing.

[R. Craig Walker]

PROFL blanks the slices of portions of the image where those slices would
be behind some stronger feature.  For example, on a strong point, you
don't see the back side.  But the algorithm gets confused at some angles
(ROTATE).  I see trouble at 90 deg and 270 deg (and small angles around
those) where major parts of the image are blanked.  I also see cases where
portions of bright features are blanked that shouldn't be at some other
rotations.  That effect seems to be source dependent.

If you do something like the following loop with DOCRT=1 you can find the
bad areas pretty fast.

for i = 1 to 36; rotate=i*10; print rotate; go; wait profl; end

I don't think you need a special image to excite this problem - at least
it is there for the two that I tried.  If I'm wrong, let me know and I'll
try to provide a concrete example.

This is on MacOSX with a midnight job a few days ago.

Cheers,

Craig

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    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
    Phone  575 835 7247        P. O. Box O
    Fax    575 835 7027        Socorro NM 87801   USA
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