DebugX.Log("Interpolating unset height cells - " + knownHeights.Length + " known heights / "+(heightmapSize*heightmapSize)+" cells");
for (int x = 0; x < heightmapSize; ++x)
{
    DebugX.Log(x + "/" + heightmapSize);
    yield return null;
    for (int z = 0; z < heightmapSize; ++z)
    {
        if (!(setHeights[x, z]))
        {
            float totalWeight = 0;
            float totalHeight = 0;
            float totalDistances = 0;

            //                    have per cell, a distance calc to each known cell
            //[16:34] <zeroZshadow> add the distances together
            //[16:35] <zeroZshadow> then the value of every known cell is divided by the total distance
            //[16:35] <zeroZshadow> and multiplyd by their own distance to the cell
            //[16:35] <zeroZshadow> add all the results together
            //[16:35] <zeroZshadow> next cell


            // calculate total distances from all known height cells
            foreach (float[] knownHeight in knownHeights)
            {
                float knownX = knownHeight[0];
                float knownY = knownHeight[1];
                float knownZ = knownHeight[2];

                float xDiff = (x - knownX);
                float zDiff = (z - knownZ);

                float distSq = xDiff*xDiff + zDiff*zDiff;

                // remember dist to current unknown cell, temporarily
                knownHeight[3] = knownY * distSq;

                totalDistances += distSq;
            }

            // calculate final height based on weighting each known height by its relative distance
            float finalHeight = 0;
            float totalDistancesRSQ = 1.0f/totalDistances;
            foreach (float[] knownHeight in knownHeights)
            {
                float knownX = knownHeight[0];
                float knownY = knownHeight[1];
                float knownZ = knownHeight[2];
                float ownDist = knownHeight[3];

                finalHeight += (knownHeight[3] * totalDistancesRSQ);
            }

            heights[x, z] = finalHeight;
            setHeights[x, z] = true;


        }
    }
}