Curve Network - Fail - Help!


Anyone know why this curve network is failing (its my first attempt at one).

My guess is at least two of the long curves are joined. Split them into separate curves and try again.

When asking why something does not work upload the file if possible. Use the small vertical arrow in the tool bar above where you type your post.

yes, the blue curve is a closed single curve. so is the pink curve. I need to break these at the end pts?

Split at end points and try again.

Have a look at the Help topic for the command. It does a good job of describing how open and closed curves need to be arranged for the command to work.

It will help to keep in mind that the topology of a NURBS surface is a rectangle.
If your input curves are laid out like a mesh it will work.
If your curves are closed in one direction and open in the other, the rectangle is rolled into a tube and two of the opposing sides are joined in a seam.

Thank you John and David, That seemed to fix the issue. Two artifacts formed in the surface though:

  1. A strange transition between the curves – not averaged or smooth or controllable. I could add more curves, but that doesn’t seem like it will overcome the basic transition problem. I expect a smoother fade out between curves and would be nice to control the rate of change between them (linear or non). I assume I am doing something wrong?

  2. A blowout on the end. Why did this occur, why does the surface not conform to the curves?

  3. How to make the surface display less faceted?

I’m use to subd modeling and not yet sure how to get the most out of nurbs.

Transition Issue

Blowout Issue

Some of what you are seeing appears to be visual artifacts due to a coarse display mesh. You can change the settings DocumentProperties (or Properties in the File menu tab) > Mesh. If Jagged & faster is selected switch to Smoother & slower and see if that helps. Further refinement is available by selecting the Custom option.

If possible post the file with your surface.

NetworkSrf always creates smooth, degree 3 surfaces without creases or curvature discontinuities. If an input curve has a kink or curvature discontinuity NetworkSrf will effectively smooth it out. It looks like several of your curves have kinks. You might try splitting the curves at the kinks and generating several surfaces.

The surface from curve network is the trickiest command to master, but well worth the effort. Here is a free overview video from my Rhino 5 course at lynda. There are two whole chapters (11 & 12) on organic modelling techniques.

If you’re not a member, here’s a link for 10-days free. Woot.

I changed the file to smoother and slower and this made it smoother but didnt address the main issues. Here is the file:ship 005.3dm (544.4 KB)

The original two issues still exist.

Thanks for the 10 days free…I’ll check it out.

Hi MIke - I’d add a section curve or two down right near the end there.

I just did the top half here.
CSec(Curve menu > Cross section profiles) with Closed=Yes. Then Split the result with the pinks. One of your section curves does not intersect the pink rails, by the way - you canb get away with it, but you might want to check


Which transitions do you find strange exactly? The surface is going precisely through your curves. If there’s a transition you don’t like, you need to losen up the curves a bit or edit them to get what you’re looking for.

A good process for you might be to activate History > then create your NetworkSrf > now turn on the Ctrl Pts (F10) for the curves > move the points around > the surface should update with these changes > do it til you get what you’re looking for.

Don’t use netwerk surf. It’s supposed to be Rhino’s version of a boundary surface but it’s just not accurate or smooth. Run a curvature graph on a netwerk surface. You’ll see all the problems. The power of Rhino is being able to point edit surfaces.

Good suggestion! There is a technique using rail sweep that can get you very close with far fewer curves and frustration.

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