Hi nos, also in some cases you might want to use the Flow command in Rhino instead of FlowAlongSrf.

The Flow command uses curve objects to define the transformation, from a base curve to a target curve. That may be a bit easier to visualize the result, I believe the distance as traveled along the base curve will map to distance traveled along the target curve in that case.

FlowAlongSrf on the other hand does not map distance to distance in a direct 3D distance sense - instead it will map between the UV space of the base surface to the UV space of the target surface. So this means that things like compression of the UV parameter space in the target surface (things like surface control points unevenly distributed) will result in uneven distribution of the morphing as well.

With the curve-based Flow command being distance based it may be easier to get a distance preserving result.

- Michael