Need Help Clean surface modeling

Hey guys,

I am working on a model that I have already built in solidworks, but now I would like to rebuild it in rhino because I no longer have access to solidworks. I have an outline of the curves I am trying to create into a surface. I also have created a surface from network of curves, but It seems that their is a cleaner way to make the surface so that when I mirror it, it is perfect and tangent. I have also attached an image of the rendering from solidworks.

Invisible Chair.3dm (2.2 MB)

One way to get at this type of pillowy surface is to use Loft with the Loose style. See the attached file- the curves are not ideal but you can get the idea- the horizontal curves are aligned to the control points of the vertical curves - some cases maybe not exactly in this example, but that is the goal. The result of a Loose loft of curves placed at deegree 3 curve control points is a surface that follows those curves exactly.

Invisible Chair_PG.3dm (1.1 MB)


The other way is to split the input curves at rounded corners, join the middle curve, and use _NetworkSrf with perspective of rebuilding later. It might be more manageble for mirroring.

Invisible Chair___.3dm (105.8 KB)

@0netech i think the goal is to prevent this :point_down: upon mirroring ; )

@pascal what did you use for the loft curves? the white ones? mine has an opening in the middle when i try those.

That’s what you have _MatchSrf with “Average surfaces” option for.

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The white curves plus the Point option to finish the loft at the ends of the vertical curves.


Awesome, thanks @pascal. That seemed to work quite well. I didn’t
realize there was a point option. I’m assuming you guesstimated on
the white curves to eventually get a form you were happy with?


@0netech I am looking at the surface you ended up with. I like the way the isocurves flow,
but I am a little confused with your explanation for achieving this. Maybe you could expand or break it down a bit more.

Thanks, Appreciate it.


Hi Tristan- the white curves are all edited copies of the base curve- this is needed if you really want the surface to stay clean- I would have probably built new curves if I were doing this from scratch, but I used yours and yes, just fiddled the points on the intermediate curves- basically removing, as much as possible, the ‘corners’ and making the curve as even as possible moving to wards the center point- ideally a circle or close to it, but that is seldom practical. Use Loft with History so you can noodle some curve points to fine tune.


OK, sorry. You can use _Split command with “point” option to split the chair edge curve at the rounded corners to get three segments (you can see the way it is split in my 3DM file). You _Join the two halves of the curve in the middle. After that you run _NetworkSrf, picking up all the curves I used in my example. After you get the surface, you can _Rebuild it if you like to reduce the point count, and smooth it out a bit (this is optional). Then you _Mirror the seat using End snaps. After that you can apply _MatchSrf with curvature continuity, making sure “Average surfaces” being checked.

I am giving you command names here, as they are universal. You can check each command, and its options in Rhino Help.

It is up to you which method to use. Mine creates some tension in surface curvature at the corners (run _CurvatureAnalysis to see that), but is easy to handle, and match surfaces. With Pasclal’s you can get really nice surfaces, but all the points converge in the middle, and sometimes you get artifacts because of that (it is fixable though).

@pascal is it possible the _Loft dialog box to have a slider which would control how much the input curves pull/influence the generated surface?

Happened to notice a history hiccup with loft yesterday: If the point command line option is used and a point existing in the file is selected, history won’t update when that point is moved. History will update using an existing point when selected along with the curves (not using the command line option). Not sure if that is as intended. I didn’t even realize before you could choose a point without using the point option.

I guess that is ‘expected’. The Point option looks for a 3d location, not a point object. But, I hear you, it’s always seemed a little ‘not quite there’ to me - in general, apart from dimensions, Object snaps are not part of history - that is, the object snapped to does not go into the History of whatever command you used.


got it. thanks


I do not recommend making half of a surface and then mirroring it. The center seam will stay there and can cause potential problems with later editing.

I suggest making half of the lines, then mirroring those. You can join lines where it helps. Now, make your surface as a single piece in one step. There should be no seams, so you can (if needed) turn on control points and continue editing.

If the surface looks off, delete it and adjust the curves. Its a simple, single step to repeat the surface build and BAM! you’re back to where you were … with a better or cleaner surface.

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Thanks, that’s what I was guessing. Maybe the thing that could be addressed is that loft can actually input existing geometry points when the command line is asking for ‘curves to loft’ without choosing the ‘point’ option?

Edit: And sorry for the slight off-topic, thought it might be helpful for the OP to know.

Awesome suggestion. It worked first time no problem.
Thanks @shultzeworks.