I was applying crackle to a ground plane and got tired of the way it has
occasional large flat areas due mostly to the fact that it's based on points
in 3D space. So I made my own 2D "crackle" function to use instead.

It's slow, so that's a significant tradeoff. But it mostly fixes the problem
of large flat dark areas.

In case anyone's interested, I'm posting it here:

// 2D Crackle function by Slime ( http://www.slimeland.com/ )
#declare Crackle2DClamp = function(x) {
 x - floor(x)
}
#declare Crackle2DPointDist = function(x, y, cellx,celly) {
 sqrt(pow(x-(cellx + Crackle2DClamp(f_noise3d(cellx,celly,0 )*10000)),2)
  +pow(y-(celly + Crackle2DClamp(f_noise3d(cellx,celly,10)*10000)),2))
}
#macro testAllPoints(skipnum)
 #local counter = 0;
 #local _x = -2;
 #while (_x <= 2)
  #local _y = -2;
  #while (_y <= 2)
   #if (abs(_x) != 2 | (_x != _y & _x != -_y))
    #if (counter != skipnum)
     Crackle2DPointDist(x,y, fx+_x,fy+_y)
     #if (counter < 20)
      #if (counter < 19 | skipnum != 20)
       ,
      #end
     #end
    #end
    #local counter = counter + 1;
   #end
   #local _y = _y + 1;
  #end
  #local _x = _x + 1;
 #end
#end
#declare Crackle2DSecondNearPoint = function(x,y, fx,fy, nearestdist) {
 #local counter = 0;
 #local _x = -2;
 #while (_x <= 2)
  #local _y = -2;
  #while (_y <= 2)
   #if (abs(_x) != 2 | (_x != _y & _x != -_y))

    select (
     abs(nearestdist - Crackle2DPointDist(x,y, fx+_x, fy+_y)) - 0.000001,
     min(testAllPoints(counter)),

    #local counter = counter + 1;
   #end
   #local _y = _y + 1;
  #end
  #local _x = _x + 1;
 #end
 0
 #local testnum = 0;
 #while (testnum < 21)
  )
  #local testnum = testnum + 1;
 #end
}
#declare Crackle2DNearPoint = function(x,y, fx,fy) {
 min(testAllPoints(-1))
}
#declare Crackle2DHelper = function(x,y, nearestdist) {
 (Crackle2DSecondNearPoint(x,y, floor(x),floor(y), nearestdist) -
 nearestdist) / sqrt(2)
}
#declare Crackle2D = function {
 Crackle2DHelper(x,z, Crackle2DNearPoint(x,z, floor(x),floor(z)))
}

Use like:

pigment {
function {Crackle2D(x,y,z)}
...
}

Enjoy.

 - Slime
 [ http://www.slimeland.com/ ]

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