protected int findClosestHeightIndex(Vector3f position, TerrainPatch patch) {

        int x = (int) position.x;
        int z = (int) position.z;

        if (x < 0 || x >= patch.getSize() - 1) {
            return -1;
        }
        if (z < 0 || z >= patch.getSize() - 1) {
            return -1;
        }

        return z * patch.getSize() + x;
    }
Finds the closest height point to a position. Will always be left/above
that position.

@param position
           the position to check at
@param patch
           the patch to get height values from
@return an index to the height position of the given block.
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/picking/BresenhamTerrainPicker.java