# Make surface from close curve

I am not sure how to make a surface from a curve which is not flat.curve.3dm (44.9 KB)

you can make a extrusion and then trim it with your curve

Thank you. Is it possible to make the surface with curve without trim?

yes but whatâ€™s the point? if you donâ€™t provide more information about the curve, the objective, the adjacent surfaces if there is any etc. with just a curve the options could be thousands

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I am wondering how to make surface with close curve. For instance, draw a circle, then create a surface from the circle.

If the closed curve is planar, like a circle, then use PlanarSrf (Surface>From planar curves).

One method to create one possible surface from the curve is to Split the curve into four segments. Use EdgeSrf to create a surface using the four segments. Important - the resulting surface will have singularities at the ends of the curve segments which can cause problems in other operations.

As Diego Krause said there are thousands, actually an infinite number of possible surfaces which fit a single curve.

Every untrimmed surface in Rhino has four sides. One, two or three sides can have zero length. In general surfaces with sides with are tangent at adjacent ends should be avoided if possible.

@hungwai.lim
Or `Split` at top and bottom and `Loft` - but again thereâ€™s singularities at top and bottom to look out for.
HTH, Jakob

I donâ€™t know that it counts as a singularity in this case - there are no collapsed points if you work from four segments. Still not a good idea, having adjacent edges tangent, as a rule; but to pick nits, I think it is a different situation than a singularity.

-Pascal

Mathematically it is a weak singularity because there u and v directions coincide and are not unique. One result of ,the singularity is problems occur at the singularity if an attempt is made to extend such a surface by increasing the parameter range (which generally works will with surfaces without singularities.) The surface does not extend at the singularity. Other problems can occur because the surface normal vector is not well defined at the singularity.

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How about using the â€śpatchâ€ť command to make a nice approximate surface?

Surface from edge curves. Not pretty but it works. Split the curve into 4 segments first.surface.3dm (320.3 KB)

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Thank you all. I have tried all suggestions and I learned a lot. I found Curve Network also possible if I split the curve to 4 curves.

CurveToSrf.3dm (795.0 KB)

I check zebra and found _EdgeSrf and _NetworkSrf are same, but Patch is different.

As a beginner I still not quite get about the singularity in loft surface.