Ron Parker <par### [at] my-dejanewscom> wrote:
: How to decide if there's really an intersection there?  If the common
: operation is intersection, should we throw the intersection away or
: keep it?  I think this depends on whether we're entering both objects,
: leaving both objects, or entering one and leaving another.  In the
: first two cases, keep it.  In the last case, throw it away.  For
: union, always keep it.  For merge, keep it using the same criteria 
: as for intersection.  Difference, of course, does not exist as a CSG
: type, but the proposed intersection rules seem to do the right thing.

  Note that the coincident surfaces problem (this is a so used term it should
be abbreviated CSP :) ) can also occur with objects not in the same CSG.
  Also note that a very special case of CSP occurs when a light source is
exactly on a surface: Povray can't calculate accurately if the light source
is inside or outside the surface, so black spots will appear in every
place which is illuminated by this light.

-- 
                                                           - Warp. -

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