Another Problem with CreateSolid

I know this is a perennial problem in Rhino, but I’ve tried most of the tips from searching the forum and I still can’t create a solid from these surfaces. I’ve extended all of the surfaces and ensured they intersect. I don’t believe there are any extraneous surfaces or nonmanifold edges. But I still can’t create a solid.

I’m running Rhino6 for Mac, Version 6 (6.30.20288.16412, 2020-10-14)

Any suggestions?

cockpitSample.3dm (1.0 MB)

Hello - it llooks to me like these two are the ones:

They intersect in two places - if you use these curves to trim off the
It you trim lower three smaller pieces and just give CreateSolid the larger one, it works.

(Your surfaces are massively dense with control points:

usually a bad sign - you might want to simplify things - what are you making?)


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Sorry, I tried trimming surfaces and still couldn’t get it to work.

This is part of a 3D printed model plane. The original design was done in Fusion 360 and I exported the Fusion model as iges and imported into Rhino. But the imported surfaces didn’t form a closed solid to Rhino’s satisfaction, so I’ve been trying to reloft the surfaces to get a solid. I started by taking half a dozen or so isocurves in each direction, then extending those curves to enlarge the surface so as to ensure it would intersect with its neighbors. Then I used Networksrf to generate a new surface.

I think I see the problem, now. Part of the eyebrow surface is outside of the side window and part of it is inside. What looks like a continuous intersection actually has a gap in the middle. I’ll revise the eyebrow surface and see if that helps.

Without having the big picture, it seems to me that you are approaching this in the wrong way. My sense is that you are going to want to have the area with these pieces smooth:

If that be that the case, you are not going to want to trim/split the surfaces like this because you will never be able to get the edges tangent.

Another apparent issue is where your windows meet. It appears that you would want the plant of roof to be smooth. That would be impossible with those windows meeting at an angle. I think you want to have a window frame there that would be curved at the top and the bottom

I have had very poor success with creating solids where surfaces met at their edges or were tangent.
Even when surfaces had the same curves in common as their edges, Rhino wouldn’t create the solid. The only way I’ve been able to create solids is by having the surfaces extend past each other so there is a definite intersection. It would be great to have those surfaces be smooth if I could do it.

This particular shape has sharp edges where the surfaces meet the planes of the windscreen and window, blending tangent edges at the back where it connects to the rest of the fuselage. This is a scale plane, so I’m trying to follow the given shape as closely as I can.

This file shows the surfaces I started with. How would you create a solid from these?CockpitOriginal.3dm (578.1 KB)

Your surfaces join together but you have gaps:

You would need to fill those gaps to close.


to find the openings. Look for NAKED EDGES

I suspect there are problems with the curves you use to generate these shape. Like here:

I suspect that you want the two roof pieces to be tangent which would require the curves to be tangent as well.

Unfortunately, I wasn’t the original author of these surfaces, and I’m trying to clean them up as best I can.

I take it your process would be:

  1. Consider each pair of surfaces
  2. Join the surfaces
  3. Analyze->Edges->Show naked edges
  4. Extend the surfaces as required to close up any gaps
  5. Trim the surfaces to create a new, tight edge
  6. Once all pairs of surfaces have been resolved, join all the surfaces and check for any naked edges
  7. Create the solid (although this step may be redundant)

Step 4 could also include revising the surfaces to make them tangent where required.

I think you need to start with the curves.

For example, at the back of your cockpit you have a big dip. My guess is that you really want this to be smooth. In that cause you need your curves to be tangent (similar as to shown in red).

Yes, I do want that to be smooth, and spliced in a wedge from the tangent points at the top. I found the tangent points by duplicating the back edges and creating a line tangent to them. I don’t know how to do something similar for the surface, so I picked a point on the centerline, interpolated curves on the surface from that point to the tangent points, and used those curves as the edges of the wedge. It is fine for what I’m doing, but there’s probably a more elegant way of creating a surface that is tangent to two other surfaces.

I’ve finally been able to get a closed polysurface from these surfaces, by basically following the procedure above. In the lower corner, I deleted the small surfaces from the original model, untrimmed the surface from the side, and extended isocurves from it. Then I moved the last control points of the extended curves to make them curl in through the walls of the surface below. I connected the ends to make a new bottom edge and used NetworkSrf to replace the original surface. That gave me a good intersection. I deleted the back face and created a new plane that I trimmed from the polysurface created by joining everything else. That gave me a matching back face.

I think you are going to have to break down and rebuild the surfaces from curves.

That has been my typical approach in the past, and what I’d been struggling to do. This time, I was able to do it without wholesale relofting of the surfaces.

Maybe you should share your curves.

Here is my revised version.cockpitSample2.3dm (1.0 MB)

BTW, NetworkSrf has become my go-to tool for relofting surfaces. It’s a pity it doesn’t show up on any of the main menus.