Hi Marc - so the reason why this result is confusing is because flow works on the underlying surfaces, not just on the visible trimmed area.

It looks like your plane was created by using the Construct > Planar command, which builds a trimmed surface and it puts the base underlying plane surface at somewhat larger size than the trim curves.

You can see this more clearly if you turn on control points for your base plane - when you do that notice how the underlying plane surface itself is actually a bit larger, like this:




That larger plane where you see the 4 corner control points is the thing that is actually used as the base surface currently, that's why the final result is not at the proportion that you were expecting.

If you use the ShrinkTrimmedSrf command (http://moi3d.com/2.0/docs/moi_command_reference10.htm#shrinktrimmedsrf) on that base plane it will shrink the underlying surface down to be snug to the trimming boundaries and then after that you should see a result more like you would have been expecting.

But also the way flow works is that it basically matches a kind of percentage along each surface, it's not going to do stuff like match a distance from the object to one edge to another distance, it's more like every point on the base plane goes to its equivalent percentage on the target surface.


Hope this helps explain the confusing result - I maybe should make the base and target surfaces automatically shrink down to fit their shaded visible boundaries to avoid this kind of confusing result. At the moment the ShrinkTrimmedSrf command will do that for you.

- Michael