Thomas Nelson <tda### [at] siriuscom> wrote:
: Bug #1: When using a difference to try and cut a hole in a plane I instead
: end up "pushing it out" (no hole, just a depression in the shape of the
: second object ) (Am I running into an "inside/outside" test?... if so how
: can I work around this?)

  This is normal behaviour.
  You have to think about the plane as if it was a solid object. which
extends to the infinity below the plane, like an infinite floor. If you
cut a part of the floor away, you get just that: a depression in the floor.
Think it as digging sand on a beach -> the beach is a plane, and when you
dig, you are differencing something from the plane -> you get a hole, a
depression.
  Note that the keyword 'hollow' has nothing to do with this. I still think
that 'hollow' is not a good term for what it really means.
  And note also, that objects in povray are not truely solid, but only
surfaces. They just act like they were solid when used in CSG (and the
keyword 'hollow' has no meaning here).
  What you seem to want, is an infinitely thin plane, not a solid floor.
First you should attach the keyword 'hollow' to the plane, so that it will
act as a really hollow object (with fog etc). Note that it will not act as
a hollow object in CSG, just when calculating fog, etc.
  If you want to cut away a hole in the plane so that you can see through,
you can use the 'clipped_by' statement. For example

plane
{ x,0 hollow
  clipped_by { cylinder { -x,x,1 inverse } }
}

(note the 'inverse' keyword; 'clipped_by' works like 'intersection' but it
doesn't add the surface of the second object)

  The 'hollow' keyword also allows you to put media inside the plane.

-- 
                                                           - Warp. -

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