Eliminate a kink in a surface

In the attached file I have frames to create a surface.I have little (to no) flexibility in the outer profile, except that at the right I have extended the curve up. The green dash line is where I would trim.

The problem I have is I get this kink. EdgeSrf, Sweep2, NetworkSrf all create this same kink. I know its a tough spot but the amount of kink is excessive.

Problem27.3dm (394.2 KB)

How can I build without getting such a kink?

It’s hard without more info about what the shape should be like there, but I’d try to trim that shape and not build it into the edges - precisely because of the effect you see there - the shape is propagated into the surface structure.

As an aside, the word ‘kink’, in Rhinospeak, has come to mean something pretty specific - that is a hard corner in a curve or surface - where Explode would split the thing up. This is more of an artifact, or twist… or wave or whoopdedoo, I think.


I got an email suggesting that I use Patch. That gave the shape (but oddly with mirror copied frames, one side gives a proper fit while the other side creates a rectangle that I have to trim.

I don’t know if this has to do with having used Patch or not but, after that other programs show up. While trying to diagnose why what I actually want to do does not work, I got this simple example of something does not work.

If A is the original shape and Z is an extruded shape. Then

Red = A - Z
Black = A AND Z


Red + Black = A

However, adding Red + Black gives “Boolean union failed.”

Problem28.3dm (194.1 KB)

This makes me think I have some setting wrong somewhere. What might that be?

Patch might work well enough - it has the advantage I mentioned of making that complex edge a trim of a larger more rectangular surface. Is there no information about surrounding surfaces at all? It the curves suggest to me a relatively simple and understandable underlying shape may be lurking there some place.

Problem27_Patch_PG.3dm (221.6 KB)


Is there no information about surrounding surfaces at all? It the curves suggest to me a relatively simple and understandable underlying shape may be luring there some place.

Problem28 shows the final shape of the part. When I was thinking it needed to be done with a networksrf/sweep, I knew the surface would not be able to stretch all the way around the curve. There are parts that go on top and bottom of this (and some details that get added). Finale trim shape looks like this:

I am still having the problem in Problem28 though. High tolerance operations fail with this part/surface. For example, In problem 28, I extract a piece from the surface then try to add it back in. That fails.

When I wanted to make this image, I tried subtracting the final top piece and that failed. I ended up subtracting a simplified version of it instead for illustrative purposes.

When I try to insert a solid in the space where the black piece is shown (see above), I cannot get a boolean union to work (that’s why I tried seeing if the part I cut out would go back–and it does not).

Methinks, I need to do something while creating the path or afterwards to make it work here.

I meant, what is going on outside the complex border curves, that determines the shape of the surface - it seems at least likely that there is more to this outside the curves than we know about - having info about that would help a lot in making the right surface.


All of those here’s are empty space.Problem29.3dm (42.1 KB)

The attached file shows the whole shape. The outer lines here are the boundaries of the surface.

Problem30.3dm (844.5 KB)

I am finding that, when I use PATCH, that the resulting parts do not play well with others unless the tolerance is set very low. At the suggestion here, I had been using 0.00001. To work with these parts (see attached) I have to get down to 0.01 for most things and even down to 0.1 to make some things work.

I have to do a JoinEdge on every edge produced by PATCH. This suggests to me that the PATCH command is not generating surfaces that are very close to the border shape (at least with my settings). I don’t see a tolerance setting on PATCH. Is there any way to get the surface edge very close to the shape edge?