Smooth Voxel Terrain, Part 2 (2012)(0fps.net)

  The second issue is that solving an overdetermined linear least squares problem is much more expensive than taking a few floating point reciprocals, and is also more prone to blowing up unexpectedly when you run out of precision.  There is some discussion in the paper about how to manage these issues, but it can become very tricky.  As a result, I did not get around to implementng this method in javascript (maybe later, once I find a good linear least squares solver…)

  initialize point at center
  for i = 1, 8 do
      project point onto each plane
      point := average of projected points
      constrain point to reasonable range
  end