Hi all,

I am working on a macro to generate tiled floors (or walls) and stumbled on
a problem I had before. When using superellipsoids I get strange black
strips on certain tiles (in the example you can see them on the centered
tiles).

Does anyone have an idea what causes this and how I can get rid off it?

Here's the code:

camera
{
 location <0, 6, -20>
 look_at  <0, 0, 0>
 right x * image_width / image_height
}

global_settings
{
 ambient_light rgb <1, 1, 1>
}

#declare singleTile =
 difference
 {
  superellipsoid
  {
   <0.2, 0.2>
  }
  box
  {
       <-1.2, -1.6, -1.2> <1.2, 0.8, 1.2>
  }
  translate <0, -0.8, 0>
  scale <0.5, 0.5, 0.5>
 }

sky_sphere
{
 pigment
 {
  gradient y
  color_map
  {
   [0.0 rgb <1, 1, 1>]
   [0.2 rgb <0.8, 0.9, 1.0>]
   [0.5 rgb <0.6, 0.7, 1.0>]
   [0.8 rgb <0.8, 0.9, 1.0>]
   [1.0 rgb <1, 1, 1>]
  }
 }
}

light_source
 {
  0 * x
  color rgb <1,1,1>
  translate <-20, 40, -20>
}

plane
{
 y, 0
 pigment
 {
  rgb 1
 }
}

#macro tiledFloor(tileWidth, tileDepth, tileSpace, xTiles, zTiles,
isCentered)
 #declare zPos = 0;

 #if (isCentered = 1)
  #declare xCenter = ((tileWidth + tileSpace) * xTiles) * -0.5;
  #declare zCenter = ((tileDepth + tileSpace) * zTiles) * -0.5;
 #else
  #declare xCenter = 0;
  #declare zCenter = 0;
 #end

 #while (zPos < (xTiles * (tileDepth + tileSpace)))
  #declare xPos = 0;
  #while (xPos < (xTiles * (tileWidth + tileSpace)))
   object
   {
    singleTile
    pigment
    {
     rgb <0.8, 0.9, 1.0>
    }
    scale <tileWidth, 1, tileDepth>
    translate <xCenter + xPos, 0, zCenter + zPos>
   }
   #declare xPos = xPos + (tileWidth + tileSpace);
  #end
  #declare zPos = zPos + (tileDepth + tileSpace);
 #end
#end

tiledFloor(12, 12 , (3/8), 10, 10, 1)


Have a fine day, nUMBc
------------------------------------------------------------------------------
We don't stop playing because we get old; We get old, because we stop
playing!

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Attachments:
Download 'tiles001.jpg' (112 KB)

Preview of image 'tiles001.jpg'

Wasn't it nUMBc who wrote:
>Hi all,
>
>I am working on a macro to generate tiled floors (or walls) and stumbled on
>a problem I had before. When using superellipsoids I get strange black
>strips on certain tiles (in the example you can see them on the centered
>tiles).
>
>Does anyone have an idea what causes this and how I can get rid off it?

I could be wrong, but it might be related to this bit of the
superellipsoid documentation, even though your values aren't really what
I would call "very small".

    Very small values of e and n might cause problems with the root 
    solver (the Sturmian root solver cannot be used). 

You could make small changes to the values, <0.18, 0.2> seems to render
cleanly in this case, but the artefacts might possibly come back when
you move the camera.

Alternatively you could use the isosurface f_superellipsoid which uses a
different solver and doesn't seem to exhibit the problem.

In this particular case the isosurface superellipsoids render just as
fast as the CSG ones.

#include "functions.inc"
#declare singleTile = 
 isosurface {
  function { - f_superellipsoid(x,y,z,0.2,0.2)}
  contained_by {box {<-1,0.8,-1> <1,1,1>}}
  max_gradient 1
  translate <0, -0.8, 0>
  scale <0.5, 0.5, 0.5>
 }

-- 
Mike Williams
Gentleman of Leisure

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