Surface "ripple" / tangency issue when creating a "blend" surface between two other surfaces

I have been trying to create a surface that smoothly transitions with the tangents of two neighbour surfaces.

Countless solutions in, using both network surface and sweep2, I am always getting this “ripple” discontinuity instead of a smooth tangent, no matter how I create them:

Here is one of the many solutions I have tried with the ripple problem: Ripple (95.7 KB)

I have tried adding more V curves, getting the isocurves from the surfaces and blending the control points, rebuilding the curves… nothing seems to get rid of these ripples.

Does anyone know what the ripples and lack of tangency issue is caused by?

You have created too many section curves, and the way you are using them is “forcing” the shape to both NetworkSurface and Sweep2 functions, so they are not really expressing any usefulness.

You should use few and well placed sections/curves, just enough to describe the “bounds” and any relevant or wanted detail inside.
(This is just normal rhino stuff, but yes, it’s the same in grasshopper)

You can extract sections, make blend curves, and finish with network surface, all in grasshopper.
Or use some script block that mimic the “blend surface” rhino command in grasshopper.

How would you like to proceed?

But actually, I’ve tried to do that on rhino first, there is a problem:
your input surfaces already have some small “ripple” inside.

You should want to solve this first. Maybe by rebuilding?

Your starting surface have 3 different “densities”/parametrization inside.
That make you have “ripples” in that surface alone:
2021-01-06 19_47_50-Window

Anyway, this is with 3 simple c# scripts: (shrink, extend, blend)
(the blend one comes from another user from the forum but i cannot remember who…)

Ripple (88.9 KB)

This could be a solution, if the surfaces were ok to begin with…

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Thank you so much! I explored this for a while and it worked :slight_smile:
I tried looking at the definition in rhino common but I don’t really understand what shrinksrf does and how it helps in this case?

I’m only left with an issue where I need to get the surface to be tangent to a third, I doubt there is such a command with multiple surfaces right? I’ll probably have to find a way to make one surface out of two.

The same as “ShrinkTrimmedSrf” in rhino.
Extending the surface with c# would result into the original untrimmed surface, extended.
(People probably use plugins for this kind of stuff… )

if your new surface have 4 borders, it’s doable.
If it is a pentagon or such, that’s a problem.

Usually I use grasshopper to pick multiple edges (tangent each-other) to make a new single surface that have theirs normals, thus making it possible to use commands like NurbSurface or loft.

related Using polysurfaces-edges as a single edge

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Thanks!! That looks really interesting for my case too :slight_smile: