Right now, the Morph Brush's area of influence is a sphere centered around the mouse pointer.  This means that, for example if you're trying to smooth out the inner elbow when the arm is bent, it's VERY hard - you can create custom groups with group editor and restrict the tool to just that group, but it's a pain and you have the problem of what will happen when the tool goes to the edge of the group (basically that's how Poser 7's morph brush behaved).

With an "along surface" option, the influence of the tool would be just a radius of points that are connected to each other on a continuous surface.  In the example of trying to smooth the inner arm, you could work with those polys even though they might be right up against, or even intersecting with, the neighboring joint's polys.

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