On Sat, 02 Feb 2002 10:55:45 +0100, "Thorsten Froehlich" <tho### [at] trfde> wrote:
> In article <3c5b0ee1@news.povray.org> , "Tom Melly" <tom### [at] tomandlucouk> 
> wrote:
> 
> > What are the difficulties of implementing, or the disadvantages of having
> > some sort of automatic precedence?
> 
> The coincident surface problem is exactly this.  Ray-tracing works by what you
> call "automatic precedence", that is sorting the intersections found.
> However, when a surface is at "exactly" the same place the intersections don't
> really have to be and mostly are not because the precision available is
> limited and causes some intersections to appear slightly closer than others.
> As this effect changes from ray to ray, you see the coincident surface
> problem.
> 

This may be a completely stupid question... But couldn't it be set up so that the user
can specify a precedence in cases where these things do happen? If the
user could overide the automatic precedence sorting I would think the problem
would disappear. It could be made to effect only the next object in a CSG or
something,
so that only those objects effected by it are overided.

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