Sketch of greedy meshing in 3D

gistfile1.js

var map = getChunkBitmap()
  , boxes = []

for(var z=0; z<CHUNK_Z; ++z) {
  for(var y=0; y<CHUNK_Y; ++y) {
    for(var x=0; x<CHUNK_X; ++x) {
      
      if(map[x,y,z]) {
        var w = 0, h = 0, d = 0
        
        //Compute width 
        while(w+x < CHUNK_X && map[x+w,y,z]) {
          ++w
        }
        //Compute height
        while(h+y < CHUNK_Y && all(map[x...x+w,h+y,z])) {
          ++h
        }
        //Fill cube
        while(d+z < CHUNK_Z && all(map[x..x+w,y..h+y,d+z) {
          ++d
        }
        //Add box
        boxes.push([[x,y,z],[x+w,y+h,z+d]])
        //Clear array
        map[x..x+w, y..y+h, z..z+d] = 0
      }
    }
  }
}

return boxes