/*
Author: Nathan Kopp
Date: Feb 26, 2000
This example demonstrates run-time scoping using the POV scripting language.

If you don't understand the term 'scope', then just ignore this message.  It
is posted here for a discussion in povray.unofficial.patches.

The call to makesph() will generate a while sphere.  The call to makesph2
will generate a red sphere.  The variable 'col' is resolved differently
depending on where and when the macro is called.
*/

#version 3.1;

camera
{
  location  <0.0, 0.5, -4.0>
  look_at   <0.0, 0.0,  0.0>
}

sky_sphere
{
  pigment
  {
    gradient y
    color_map { [0.0 color blue 0.6] [1.0 color rgb 1] }
  }
}

light_source
{
  <-30, 30, -30> color rgb 1
}

#macro makesph()
  sphere { 0.0, 1
  texture {
    pigment { rgb col }
    finish{specular 1}
  }
}
#end

#macro makesph2()
  #local col = <1,0,0>
  makesph()
#end

#declare col=<1,1,1>;

object{
  makesph2()
  translate -x
}

object{
  makesph()
  translate x
}

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The example is very interesting indeed.

> The call to makesph() will generate a while sphere.
I found the "while sphere" to be an intriguing concept (I first
tried to imagine what it was before reading any further... ). But it is a
perfectly logical concept: 2 nested while loops surely form a while sphere
:-)


Philippe

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