It appears that when you use the smooth height tool at the edge of the height map, points on the brush outside the mesh get treated as a value of 0 - so points on the edge of the height map rapidly approach a height of 0 while the other points in the brush area do more reasonable things. I can't imagine this ever being expected/useful behavior . Is there any way it'd be possible to make the edge points acts like a clamped texture for purposes of the smooth tool? Meaning, points sampled outside the height map return the value of the height map edge. I would think that'd result in much more reasonable smoothing results. Or mask the brush so it only considers points actually on the height map when averaging?