Best way to surface smoothed corner 3D curves

This is a cover for a small boat. The best method I like is network surface, but I have to somewhat randomly split the forward radius corners. Patch isn’t accurate enough and loft fails.

Network surface is great if I have clear points to split, but here I have to split it kinda on the radius corners for network surface to work. Even then it doesn’t always fill in my edges and radius fully.

Hello - is that selected curve a ‘single’ curve, viewed from the side? Can you post the curves?


How would you build the physical cover? How many pieces of fabric? Where would the seams be located?

It wasn’t just a solid curve, i just did that to highlight what part I was referring too.

test.3dm (74.1 KB)

Posted file.

Like I said, I can do this fine… but I feel like I’m hacking it by having to split on the radius or around them to get network surface to work.

It’ll be two runs of fabric front to back. I do all the splitting once I Squish out the surface.

Hi Eric - I might have the wrong idea about what you intend - is this something like it?
test_Maybe.3dm (102.0 KB)


I intend to do the whole top including the back section. Maybe that is part of my issue… maybe loft/patch front then surface that back part and join.

What tool did you use? Loft?

I see you pulled a curve… did you patch/trim? I haven’t tried that but I like the smoothness.

Hi Eric - I made the blue curve in a view which ‘sees’ the profile pretty cleanly and then extruded that curve and trimmed it from the Top with the relevant curves. Note the ‘Curve view’ view has a custom CPlane that lets me draw that shape correctly. That CPlane is set perpendicular to the red line.

test_Maybe.3dm (115.3 KB)


1 Like

I think I can figure out what you did, thanks for the demo.

So, in your opinion, using network surface wouldn’t be the best method for this application?

I was basically breaking up my top curve into 4 or so splits and network curve works mostly, but doesn’t always match up my outline.

Hi Eric - if the shape is, in theory, defined by a single ‘side view’ curve as I assumed here, then I’d do it this way - in general if the edges are complex in shape it may pay to simplify the thing into a basic ‘theoretical’ shape and trim the edges rather than try to work directly from the complex edges.


1 Like

Perfect. Thanks so much!


One last thing, sorry. When I extruded the curve and trim the surface, it creates a polysurface that I can’t merge to another surface nor is it squishing correctly. I see you have a nice trimming surface NURBS.

RIGHT view, traced curve projecting to plane, ExtrudeCrv, dragged over in TOP view, used Trim.

Hi Eric - my guess is the curve is overly complex and has some tangent discontinuities - you can probably simplify the curve for a shape such as that by a lot - feel free to post what you have.


This includes my attempt and your original example.

test_Maybe.3dm (272.3 KB)

Hi Eric - your curve is degree 2 and ‘jiggly’. For a simple curve like this, even with one or two reversals in curvature, I’d use a simple degree 5 curve - Get it only about right to begin with and point edit to get the final shape, using InsertControlPoint and RemoveControlPoint if needed.

Red=My go at it, moved away so you can see the graph.(CurvatureGraph), below is your curve exploded into 3 parts.

CleanerCurve.3dm (63.4 KB)


1 Like