Flow Along Surface Issues

Hey all, I’m an architecture student working on a project for school. We have to apply detailed solids to surfaces, so I’ve been trying to use flow along surface, but I’ve been having a ton of trouble with it. Typically the result is warped, distorted, or doesn’t stretch to fit the entire surface. I think the fact that the surfaces I’m applying to are curved is making it more difficult. I’ve tried troubleshooting for two days to no avail. If anyone has any suggestions as to how to resolve the issue I’m having I would be so grateful. I’ll attach some pictures to demonstrate what I mean. The first image shows the command working the way I want it to, and the second is what the outcome usually looks like. Thanks so much.


Hi Hannah - FlowAlongSrf maps objects from the base surface UV to the target UV, so troubleshooting has to take into account both - can you post an example that does not work how you want?


Yes, the second photo I attached is the undesired outcome. The grid on the front should stretch to fit the entirely of the pink surface, ideally without any distortion to the grid itself.

Hi Hannah - I need a Rhino file with the objects, the base surface and the target surface.


Sure, I made the solids I need applied onto the surface into lines to make the file size more manageable. Thank you for looking at it, I really appreciate it. Help File.3dm (16.3 MB)

you have problems because your base surface is a trimmed plane.

Hi, thanks for looking at it. I’m not sure what you mean or how to fix this. Could you explain further?

Hello - so the problem is, there is a difference between what you see as a ‘trimmed face’ in Rhino and the face’s underlying surface. FlowAlongSrf can only use the UV of the underlying surface (or a shrunken version of that, more on that later). The extents and arrangement of the underlying surface can be seen by Untrim or by looking at the surface control points -

See how your grid of curves is on a portion of the underyling surface only, and the target surfave is not trimmed at all - so the mapping from one surface to the other seems ‘incomplete’.

here is an untrimmed surface that has the same shape as the base surface:


If I flow to a 3d surface that has the same structure:

then the flow is cleaner.

The surface structures do not need to match but they need to be similar. (i.e. not like the trimmed to untrimmed faces like you have) Sometimes it is helpful to simply rebuild the target surface to a high point count as a temporary target, because rebuilding makes for a very even UV distribution, which is generally good in that distortion of the flowed objects is minimized.


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the command works better when the structure of controlpoints is similar in both surfaces.

Thanks that makes sense. When I find myself in the position of having a trimmed surface when I don’t want one how do I create an untrimmed surface like you showed with the blue surface above?

Hi Hannah - in this case, used the edges of your surface, rebuilt, somewhat arbitrarily to six points and degree 3 - and EdgeSrf. But it may not be that straightfoward. Note it works to go the other way as well - you could make the 3d surface a trimmed one similar to the trimmed base surface - that just seems trickier to get right.