POV-Ray : Newsgroups : povray.binaries.images : Faux Dupin Cyclide Server Time
29 Mar 2024 06:40:01 EDT (-0400)
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From: Bald Eagle
Subject: Re: Faux Dupin Cyclide
Date: 18 May 2017 13:00:01
Message: <web.591dd2009364765ac437ac910@news.povray.org>
3rd:


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From: Bald Eagle
Subject: Re: Faux Dupin Cyclide
Date: 30 May 2017 13:00:01
Message: <web.592da4f99364765ac437ac910@news.povray.org>
With regard to my continuing interest in tori, esp the Clifford Torus, and their
relationship to the Dupin cyclide by geometric inversion, I was playing with
some inversion code, and ran into some strange artefacts.


Perhaps someone can see what's going on here.   It seems very strange to lose
all of the objects above a straight line.

I had another instance where just the top right quadrant got wiped out.

#version 3.7;
global_settings{ assumed_gamma 1.0}

#include "colors.inc"
#include "math.inc"

sky_sphere {pigment {gradient <0,1,0>
                      color_map { [0.00 rgb <0.6,0.7,1.0>/2]
                                  [0.25 rgb <0.0,0.1,0.8>/4]
                                  [0.75 rgb <0.0,0.1,0.8>/4]
                                  [1.00 rgb <0.6,0.7,1.0>/2]
                                }
                      scale 2
                    } // end of pigment
          } //end of skysphere -------------------------------------

light_source { <-20, 100, -200>, 1 }

camera {
 location <0, 0, -20>
 up y
 right x*image_width/image_height
 look_at 0
}

#declare Line = 0.1;
#declare O = <0, 2, 0>;
#declare R = 3;

#declare Center = sphere {O, Line pigment {Green}}
#declare Circle_C = torus {R, Line pigment {Green} rotate x*90 translate O}

#macro Inverse (Point, CircleCenter, CircleRadius)
 #local P = vnormalize (Point);
 #local C = vnormalize (CircleCenter);
 <(Point.x-CircleCenter.x)*(R*R)/(pow(Point.x-CircleCenter.x,
2)+pow(Point.y-CircleCenter.y, 2)+pow(Point.z-CircleCenter.z, 2)) +
CircleCenter.x,
  (Point.y-CircleCenter.y)*(R*R)/(pow(Point.x-CircleCenter.x,
2)+pow(Point.y-CircleCenter.y, 2)+pow(Point.z-CircleCenter.z, 2)) +
CircleCenter.y,
  (Point.z-CircleCenter.z)*(R*R)/(pow(Point.x-CircleCenter.x,
2)+pow(Point.y-CircleCenter.y, 2)+pow(Point.z-CircleCenter.z, 2)) +
CircleCenter.z>
#end

object {Center}
object {Circle_C}

#declare TCenter = <-4, 2, 0>;
#declare r0 = 2;
#declare r1 = 0.5;
// torus
#declare XT = function (TT, TP, TR, Tr) {(cos(TT) * ( TR + Tr * cos(TP) ))}
#declare YT = function (TT, TP, TR, Tr) {sin(TT) * ( TR + Tr * cos(TP) )}
#declare ZT = function (TP, Tr) {Tr * sin(TP)}

#for (Torus, 0, 1.5, 0.5)
 #declare TCenter = TCenter + <Torus, 0, 0>;
 #declare Steps = 180;
 #for (Theta, 0, tau, tau/Steps)
  #for (Phi, 0, tau, tau/Steps)
  #declare X = XT (Theta, Phi, r0, r1) + TCenter.x;
  #declare Y = YT (Theta, Phi, r0, r1) + TCenter.y;
  #declare Z = ZT (Phi, r1) + TCenter.z;
   //sphere {<X, Y, Z>, Line pigment {White}}
   sphere {Inverse(<X, Y, Z>, O, R), Line pigment {Blue*Torus}}
  #end
 #end

#end


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From: Cousin Ricky
Subject: Re: Faux Dupin Cyclide
Date: 30 May 2017 16:37:31
Message: <592dd80b$1@news.povray.org>
On 05/30/2017 12:59 PM, Bald Eagle wrote:
> With regard to my continuing interest in tori, esp the Clifford Torus, and their
> relationship to the Dupin cyclide by geometric inversion, I was playing with
> some inversion code, and ran into some strange artefacts.
>
>
> Perhaps someone can see what's going on here.   It seems very strange to lose
> all of the objects above a straight line.
>
> I had another instance where just the top right quadrant got wiped out.

I got a completely blank image, except for the sky_sphere.

I also got these warnings:

----------[BEGIN MESSAGES]----------
Parsing 16549K tokens
File 'baldeagle-inversiontest.pov' line 54: Parse Warning: Divide by zero.
File 'baldeagle-inversiontest.pov' line 57: Parse Warning: Divide by zero.
File 'baldeagle-inversiontest.pov' line 60: Parse Warning: Divide by zero.
Parsing 36707K tokens
-----------[END MESSAGES]-----------

Please note that, as I saved your post, the #version statement is on 
line 18.  If the #version is at the top of your scene file, you'll have 
to subtract 17 from the above line numbers.  I also suspect several line 
breaks introduced by the news software right about where the divisions 
by zero occur.

> #version 3.7;
>. . .
>  #for (Theta, 0, tau, tau/Steps)
>   #for (Phi, 0, tau, tau/Steps)
>. . .

Evidently, your scene requires #version 3.71;


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From: Stephen
Subject: Re: Faux Dupin Cyclide
Date: 30 May 2017 16:55:36
Message: <592DDC44.6070400@aol.com>
On 5/30/2017 9:37 PM, Cousin Ricky wrote:
> Please note that, as I saved your post, the #version statement is on
> line 18.  If the #version is at the top of your scene file, you'll have
> to subtract 17 from the above line numbers.  I also suspect several line
> breaks introduced by the news software right about where the divisions
> by zero occur.

Right you are.
Two line wraps on three lines. Copied from Thunderbird.

-- 

Regards
     Stephen


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