Got this by mail (the sphere sweep does, indeed, seem to have some noise
problem, but I don't know what causes it):


From Mar### [at] iclcom Wed Oct 10 17:03:47 2001
Date: Wed, 10 Oct 2001 14:29:09 +0100
From: Wright Mark <Mar### [at] iclcom>
To: "'war### [at] tagpovrayorg'" <war### [at] tagpovrayorg>
Subject: Povray 3.5 bug? But can't post to news server


Hi,

Sorry for contacting you direct but I haven't been able to connect to the
povray news server to log a 3.5-beta 5 bug, and found you on the TAG
list... eenie meenie.....

I only dabble with Povray but sometimes this can be useful coz I probably
try things out that others probably don't bother with anymore.

The problem seems to be related to the CSG Noise problem with two
surfaces at the coordinates same point, but it ocurrs on the Sphere_Sweep
when using anything other than a Linear Spline:

Try....

#version 3.5;

#include "colors.inc"

global_settings {
  assumed_gamma 1.0
}

// ----------------------------------------

camera {
  location  <0.0, 0.5, -20.0>
  direction 1.5*z
  right     x*image_width/image_height
  look_at   <0.0, 0.0,  0.0>
}

sky_sphere {
  pigment {
    gradient y
    color_map {
      [0.0 rgb <0.6,0.7,1.0>]
      [0.7 rgb <0.0,0.1,0.8>]
    }
  }
}

light_source {
  <0, 0, 0>            // light's position (translated below)
  color rgb <1, 1, 1>  // light's color
  translate <-30, 30, -30>
}

// ----------------------------------------

plane {
  y, -1
  pigment { color rgb <0.7,0.5,0.3> }
}

// create a curved tube object translating a sphere along a certain path
sphere_sweep {
  //linear_spline                 // linear curve
  catmull_rom_spline          // alternative spline curves
  //b_spline
  6,                            // number of specified sphere positions
  <5, -5, 0>, 1                // position, radius
  <-5, -5, 0>, .5                // position, radius
  <-5, 5, 0>, 2                 // ...
  < 5, -5, 0>, 2
  < 5, 5, 0>, .5
  <-5, 5, 0>, 1

  //tolerance 0.001             // optional
  pigment { color rgb <1,0,0> }

}

Loadsa noise where I assume the 'joins' are.

I've had a good look round and can't see it mentioned anywhere in the web
hosted newsgroups.

Hope you can help,

Cheers,

Mark.




-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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"Warp" <war### [at] tagpovrayorg> wrote in message
news:3bc4563e@news.povray.org...
>   Got this by mail (the sphere sweep does, indeed, seem to have some noise
> problem, but I don't know what causes it):

tolerance 15 or so seems to be the upper limit, it starts to remove parts
above 15.  Its shadow goes away before that.  Anyhow, it's just a tolerance
thing.

A long time ago I made some musical notes which bent around at least this
much and probably moreso.  They varied in color (on purpose) and I think I
had to raise tolerance from its default (1e-6?).

Bob H.

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