/*
This scene shows black Isosurface artefacts when the accuracy value is set
to high

*/
// Persistence of Vision Ray Tracer Scene Description File
// File: landschaft.pov
// Vers: Pov 3.5 beta 4
// Desc: Eislandschaft
// Date: 1/9/2000 (updated 6.10.2001
// Auth: Marc-Hendrik Bremer
//

#declare HQ=2;
#include "functions.inc"


global_settings {
   assumed_gamma 1.0
   ambient_light 0
   //max_trace_level 8

   #if (HQ=2)
  // Medium Quality - works for most scenes
     radiosity{
       pretrace_start 0.08
       pretrace_end   0.04
       count 35             // CHANGE range from 20 to 150

       nearest_count 5      // CHANGE range from 3 to 10
       error_bound 1.8      // CHANGE - range from 1 to 3
       recursion_limit 3    // CHANGE

       low_error_factor .5  // leave this
       gray_threshold 0.0   // leave this
       minimum_reuse 0.015  // leave this
       brightness 1         // leave this

       adc_bailout 0.01/2   // CHANGE - use adc_bailout = 0.01 /
brightest_ambient_object

     }
   #end
}


// ----------------------------------------
camera
{
  location  <0.05, 0.89, -5>//  -15>
  look_at   <0, -0.000001,  0.0>

}

background {rgb <0.3,0.3,0.5>}
sky_sphere
{
  pigment
  {
    gradient y
    color_map { [0.0 color rgb 0.5] [1.0 color blue 0.6] }
    turbulence 0.2
    translate y*-0.2
  }
}



light_source
{
  0*x // light's position (translated below)
  color rgb <0.9, 0.9 , 1> // light's color
  translate <-300, 1000, -450>
}

#declare T_SnowA =
texture {
   pigment { rgb 1 }
   finish

      ambient 0.0
      diffuse 0.6
      specular 0.3
      roughness 0.6
      brilliance 0.4
   }
   normal{granite 0.2
          turbulence 0.5
          scale 0.0005}
}
#declare T_Rock =
texture {
   pigment { rgb 0.4 }
   normal {granite scale 0.1}
}

#declare T_ARCTIC_01 =
texture{
    slope -y
    texture_map{
      [0 T_SnowA]
      [0.3 T_SnowA ] //flatter
      [0.3 T_Rock ]  //steeper
    }
}

#declare H = 0.21; // roughening<>smoothing
#declare Lacunarity = 4; // roughening<>smoothing
#declare Octaves = 6; // smoothing<>roughening (computationally intensive
higher)
#declare Offset = 0.55; // height (suggested to start as 1 in the Doc.)
#declare Gain= 1.5; // smoothing<>roughening (I used too much maybe)

#declare Fun=
function {f_ridged_mf(x,y,z,H, Lacunarity, Octaves, Offset, Gain,2)}
isosurface {
     function { y - Fun(x,0,z) } // function is applied to x,y,x and
interacted according to y
     //method 2
     evaluate 1,10,0.99
     max_gradient 6

     accuracy 0.000001    // set to 0.1 to show black parts on the iso!
     contained_by{box {-3,3}}
     texture{T_ARCTIC_01}
     scale 5
}

Post a reply to this message

Marc-Hendrik Bremer <Mar### [at] t-onlinede> wrote:
: This scene shows black Isosurface artefacts when the accuracy value is set
: to high

  So?

-- 
#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 -

Post a reply to this message

Warp schrieb in Nachricht <3bbec1ed@news.povray.org>...
>Marc-Hendrik Bremer <Mar### [at] t-onlinede> wrote:
>: This scene shows black Isosurface artefacts when the accuracy value is
set
>: to high
>
>  So?
>

Oh, sorry. This is related to the a thread in p.b.I ("is this a bug?
(~14k) - iso35_01.jpg (1/1)") where I suggested that you should change the
VFAQ about the isosurface artefacts (disappearing isos, black spots). Now it
only mentions max_gradient as a possible cause of this problems, but in my
experience to high "accuracy" values can cause similar problems. Christoph
Hormann doubted that, so I provided a testscene. If you render it with an
accuracy of 0.1 you will get iso artefacts.

This is not a bug-report or something like that, it's only a suggestion to
give a more complete answer in the VFAQ.

Marc-Hendrik

Post a reply to this message

Ok, I'll add a note about that.

-- 
#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 -

Post a reply to this message

Warp schrieb in Nachricht <3bbecf70@news.povray.org>...
>  Ok, I'll add a note about that.


Thanks. I see, you already changed it. Another suggestion would be to
mention that there is a relation between a to big container object and
max_gradient, too (see p.b.b-t "isosurface contained_by or evaluation
problem").

Marc-Hendrik

Post a reply to this message