Merging surfaces without wavy iso curves?

[eobet]

I attempted to insert iso curves so both surfaces match, but apparently the degree is still different between them so when I do MergeSrf they become wavy:

Anyone have any tips on how to merge them while keeping the iso curves straight?

mergesrf.3dm (1.5 MB)

(Background: FlowAlongSrf can’t do polysurfaces, so this is me using a lot of guides and network surfaces to attempt to build something which can unroll in a nice and evenly distributed manner. Currently, there’s less than 0.1mm deviation from these and the original surfaces.)

[pascal (Pascal Golay)]

Hm - yeah… degree is the same but point count way different

The smaller surface is chock full of fully multiple knots , = kinks,

I was going to suggest RebuildUV on both to say 48 points but the points in the results do not line up either.
It may work to go ahead and merge ugly and then rebuild the result to a lot of points - that will make a more predictable Flow target anyway.

Otherwise I would create that smaller surface from the edge of the other one.

Or, possibly, jump through a lot of hoops - is this too far off?

mergesrf_Maybe.3dm (300.7 KB)

-Pascal

[eobet]

Thank you, but for some reason, your surface has even bigger distortions than my attempt:

The kinks were my fault… I just tried different commands to insert iso curves and that one produced the first good result on a quick inspection. Here’s a new file without kinks:

mergesrf2.3dm (4.4 MB)

Guess I manually need to weak the unrolled surface in order to produce an undistorted result? Seems I can do that by moving the control points, but why am I not getting any points in the V direction? (And similarly to the “wrong” command I used above, what command can I use to insert points without destroying the existing layout?)

[pascal (Pascal Golay)]

Hello- Rebuild that merged green surface and the base surface to a lot of control points - 60 by 60 or so-

No idea if the multiple ap[proximations are building up to something too far away from what you need

-Pascal

[eobet]

Thanks for the tips! The Rebuild command gives quite a worrying preview, before producing a more “correct” result once you click OK…

However, depending on point count, I get some bumps which weren’t there before (and I’m experimenting with RebuildUV as well): EDIT: Nope, turns out the bump was from the initial network surf… oof, this is more difficult than I anticipated!

Also, the wavy ico curves still gives some small issues.

Anyway, I’ll try to continue to find ways to straighten them out, and also balance the rebuild count.

[Tom_P]

Dear @eobet
what are you trying to achieve ?
the original surface locks quite bumpy.

Projecting some parallel curves looks like this:

maybe you get closer to the desired precision if you only rebuild some target surface for a single flowed element ? (no need to work with a complex, merged surface that can’t be unrolled / flattened)

something like this:

for the green target surface you can use some combination of mesh, pull, patch (with starting-surface)

[eobet]

Those things are just test shapes. I’m planning to flow way more complicated surfaces than that (but right now, I’m leaning towards doing it in Blender, because that uses an UV map which I initially thought was more difficult to tweak, but now I suspect it still might be easier to bring the result of that in as subd in Rhino… the base/target surfaces recreated in Blender at least don’t have any bumps).

I’m just trying to find a workflow to get around the issue that FlowAlongSrf only accepts a single surface and not polysurfaces (or subd surfaces).

[pascal (Pascal Golay)]

I use Drape in many cases to get a target surface spanning seams.

-Pascal