What is pov going to do if you do a trace call from a point that is exactly
on a surface--
i) always report that surface,
ii) always report the next one it hits in your specified direction,
or
iii)  give haphazard results

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In article <3deeca39$1@news.povray.org>,
 "Greg M. Johnson" <gregj:-)56590@ao:-)l.com> wrote:

> What is pov going to do if you do a trace call from a point that is exactly
> on a surface--
> i) always report that surface,
> ii) always report the next one it hits in your specified direction,
> or
> iii)  give haphazard results

D) intersections too close to the start of the ray are ignored. You 
should still be careful with it though...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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On Wed, 04 Dec 2002 22:37:15 -0500, Greg M. Johnson quoth:

> What is pov going to do if you do a trace call from a point that is
> exactly on a surface--
> i) always report that surface,
> ii) always report the next one it hits in your specified direction, or
> iii)  give haphazard results

Depends on the surface, but in general, iii) give haphazard results

-- 
Mark

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Mark Wagner <mar### [at] gtenet> wrote:
> Depends on the surface, but in general, iii) give haphazard results

  If that would be true, then any surface with reflections or refractions
would look wrong.
  The reflected/refracted rays start exactly from the surface of the object.
(Internally there's an epsilon value added to the start point of the ray
to avoid problems, and I suppose that trace() works in the exact same way.)

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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