code: private int[] getIntBounds(BoundingBox coordbounds) {
  		int[] bs = new int[6];
  		bs[0] = getFloor(coordbounds.xmin);
  		bs[1] = getFloor(coordbounds.ymin);
  		bs[2] = getFloor(coordbounds.zmin);
  		bs[3] = getFloor(coordbounds.xmax);
  		bs[4] = getFloor(coordbounds.ymax);
  		bs[5] = getFloor(coordbounds.zmax);
  		return bs;
  	}
docs: Returns an int array of size 6 :
  - elements 0,1,2: minimum x,y,z (in grid int coordinates) of the given atoms
  - elements 3,4,5: maximum x,y,z (in grid int coordinates) of the given atoms
  @return