Tom Melly <tom### [at] tomandlucouk> wrote:
: What are the difficulties of implementing, or the disadvantages of having
: some sort of automatic precedence?

  The problem is that povray has no way of knowing that two surfaces are
exactly in the same place.
  How could it know it? When it gets the intersection points of the ray
and two objects and even when these points are very close to each other,
it still can't decide that "these surfaces are coincident". The surfaces
may just be intersecting and the current intersection point happens to be
really close to their intersection line.
  It can't do that even if the normal vectors are (almost) identical because
the normals just happen to be perturbed so that they happen to be really
close by chance.
  And how can it know that one of the surfaces is not truely in a different
(though very close) place than the other surface and that it's not just an
accuracy thing?

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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