POV-Ray : Newsgroups : povray.general : Just musing about a pattern function... Server Time: 25 Jun 2019 20:26:28 GMT
  Just musing about a pattern function... (Message 11 to 11 of 11)  
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From: Alain
Subject: Re: Just musing about a pattern function...
Date: 22 Mar 2019 20:07:09
Message: <5c95406d$1@news.povray.org>
Le 19-03-21 à 20:49, Bald Eagle a écrit :
> clipka <ano### [at] anonymousorg> wrote:
>> Because then POV-Ray has to shoot secondary rays (for shadow tests, or
>> reflections and/or refractions depending on material), and decide
>> whether or not to consider that other surface for this purpose: Is it
>> /genuinely/ coincident or just extremely close?
>> That's where the true can of worms is opened.
> Well, yes, I didn't think that there wouldn't be a string of complications in
> the ideal implementation - but a simple "if a ray from the camera intersects
> only one object then assign the designated material, if it intersects both
> objects, then assign the designated third material (which may be the same as
> either of the previous)" would at least be useful for highlighting some overlaps
> in CSG, and could give rise to some hard-to-envision effects that might make a
> useful artistic tool.
> And I suppose that part of the implementation could be an option Epsilon value
> to override the usual 1E-06 distance...
> Like I said, it was just something that popped into the noggin before I even
> really woke up.

The problem it that it may be impossible to differentiate between «there 
is only one surface at this location» and «there are two surfaces at the 
same location».

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