Does anyone have any general advice with regard to clipped_by and bounded_by
and improving rendering speed?

Is it best to use both, or does it depend on the situation? Are there any
adverse affects?

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Tom Melly <tom### [at] tomandluf9couk> wrote:
: Does anyone have any general advice with regard to clipped_by and bounded_by
: and improving rendering speed?

clipped_by:
  As you may know, clipped_by works like intersection, but it doesn't add the
surface of the clipping object to the clipped one. The advantage of this is
speed.
  Thus, clipped_by should be used when you want to clip off parts of an object
and the clipped surface is not visible. For example, suppose that you want
to add a handle to a cup of coffee with a half-torus. It's more recommendable
to make the half-torus with a clipped_by than with an intersection (or
difference) since the clipped surface will not he seen anyways (it will be
attached to the cup).

bounded_by:
  Since there are usually hundreds and even thousands of objects in a scene,
a group of objects is bounded with a simpler object to speed up ray-object
intersection tests (the intersection is first tested with the bounding object
and only if it succeeds, it's tested with the objects inside it).
  Povray automatically bounds objects, CSG, etc. so usually one doesn't have
to do it by hand.
  Sometimes, however, povray is unable to do a good job bounding certain
objects, for example intersections, differences, blobs, etc. Other objects
can't be automatically bounded (for example quartics and polys). In these
cases manual bounding may speed up considerably. (Note that sometimes you
have to specify the command line parameter -UR to stop povray from removing
automatically user bounds.)
  However it is recommendable to do so only if you know exactly what you are
doing. Unexperienced use of manual bounding may even slow down the rendering.

  When to use both?
  If you are using clipped_by and the resulting object is much smaller than
the original one, then it may be good to add bounded_by { clipped_by }

  See also: http://www.students.tut.fi/~warp/povVFAQ.html#renderingspeed

-- 
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):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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