Kenneth <kdw### [at] earthlinknet> wrote:
> Is is safe to use the exact same dimensions for the bounding box?

  Yes. Bounding boxes only affect the test whether the object is
traced at all or not. If the ray hits the bounding box then it will
also be tested against the object.

  The problem with coincident surfaces with CSG happens when it's
necessary to know which one of the two surfaces is closer (which is
necessary if the two surfaces have different textures). If they
are coincident, then it's not possible to know that, and which one
ends up being chosen depends on floating point inaccuracies.

  However, with bounding box testing there's no "which surface is
closer?" test. It's just: Does it hit the bounding box? If yes,
then trace the object too.
  (Note that the exact same ray is used to test the bounding box
and the object. The second ray does not start from the surface of
the bounding box. Thus there's no problem.)

-- 
                                                          - Warp

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