Flow Along Surface Give Bad Results

Hello, I work in footwear industry and i use a lot the Flow Along Surface, and i detect a strange behaviour in the command.

If i make the flow command in Rhino7 the result is OK, bu if i make the same command with the same parameter in Rhino8 the result is NOT OK.

Rhino7 gives the Green curve and Rhino8 give the White Curve.

Flow_Along_Surface_Not_Working.3dm (454.6 KB)

Here is the file to verify this strange behaviour.

P.S. I never heard that the flow along surface was changed in Rhino8, or maybe it was…

Sorry but i’m going back to Rhino7 because if i didn’t detect that situation my whole work was wrong and its not good for me.

Pedro Neves

Hi Pedro - I do not yet know what the difference is, but, why are you flowing objects larger than the surfaces? Is that deliberate?



Hello Pascal, yes is deliberate, the objects to morph is larger than the surfaces.
If you try to make the flow command in Rhino7 and in Rhino 8 you have different results. the curve in rhino 7 is like a offset of the Trimed surface and that behaviour its ok, in Rhino8 the curve has a strange form in the quadrants of the curve.


Hello Pascal

This picture show the result

Rhino7 flow make the green curve, and Rhino8 make the red curve, if the algorithm is the same the result should be the same.


Hi Pedro I understnd the problem in the result - you notice it occurs where the curves fall off of the surfaces - my conjecture of the moment is that extending the surfaces may have changed in V8. I am trying to find that out.


Hello Pascal, yes extending surfaces also didn’t work right ex: when we put a length to extend it makes a random(very big) extend, also whatever we put in the command prompt in the preview always shows a line extend preview , and the result is always a Smooth extend surface.

try in this file.

Extend wrong.3dm (164.2 KB)

Pedro Neves

Hi Pedro - in both V7 and V8, the flow outside the boundaries of the base surface becomes something like guesswork. I see that in this case at least, the transition is certainly uglier in V8 - still looking for why - but from what I understand from the developer, you probably don’t want to rely too much on results outside the borders of the base surface, even in 7.
i.e. make your surfaces oversized by a bit before you flow.

Hi Pascal,

Is totally the opposite, its very important the results of the objects outside the boundary its the reason for that command works for me, and in footwear industry.

I cannot do that because is the only way i can control the morph, the surface had to have the same boundary size the plant of the shoe sole.

Here the reason why in this file
The flow surfaces in v8 flow are very bad as you can see, in v7 are very good.

Please give me the old Rhino7 Flow along Surface please, please.

In my previous posts i talk about the extend surface that is not working.


@PedroNeves - we, that is, the developer, has found the change that causes this difference - this change fixed a different messiness at the edges of surfaces in flowing - I do not know yet which evil will be kept or whether it is possible to eliminate both.


Hi Pascal, for me it will make a big diference that the flow works like in Rhino7 in that particular situation, the surfaces in Rhino8 are unusable for me as you can see in the new file that i send , there will be no choice, i will have to go to Rhino7 to make a Flow Along Surface.


Yep, I saw that too - thanks -
RH-80360 ExtendSrf - distances incorrect


Also whatever we put in the command prompt in the preview always shows a line extend preview , and the result is always a Smooth extend surface

Ugh, I see that too… thanks

RH-80362 ExtendSrf: Always smooth


RH-80360 is fixed in Rhino 8 Service Release 4

RH-80359 is fixed in Rhino 8 Service Release 5 Release Candidate