POV-Ray : Newsgroups : povray.binaries.images : trace() is unreliable on lathe : Re: trace() is unreliable on lathe Server Time
28 May 2022 13:52:12 EDT (-0400)
  Re: trace() is unreliable on lathe  
From: Kenneth
Date: 28 Apr 2022 02:10:00
Message: <web.626a2e4634e735428d86850a6e066e29@news.povray.org>
I have come up with an idea that might be a fix for the precision issue-- at
least for some of your lathe objects. I have not tested it thoroughly though; I
used only frame 3 of your animation for my test, the 'cubic lathe 1' object.

That shape uses your (first) array[6] for its construction points...

  { <-3, 1>, <0, 2>, <3, 4.5>, <3, 9.5>, <0, 12>, <-3, 9.5>,

....so I made an 'intersection' of the resulting lathe object with a box:

#case (CUBIC)
  box{-6,<6,12,6>} // same y-height as in array
    lathe { cubic_spline List (uv_Ctrls)  rotate 0 }}  #break

Even with Offset = 0, it looks like the trace at the top was successful. Perhaps
the coincident or overlapping y=12 values have somehow removed the tiny
precision error. HOW, I don't know.  ;-)

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