Loft Problem with guide curves


I’d like to close the side of this geometry in rhino. Loft should be perfectly capable of doing this, but gives a weird curved surface. Could anyone help me in understanding what’s happening here? Why does loft behave this way? Or is there a better way to close this geometry? The curves are just guidelines, if you feel it could be done prettier/smoother be my guest :slight_smile:
LoftProbleem.3dm (618.6 KB)

A much better approach would be to create a separate surface for each area where the cross section curves are straight and then join the individual surfaces into a polysurface. Create a fillet or blend surface at the rounded corner.

Loft is not always the best way to create surfaces in Rhino. Other commands to create surfaces include Sweep1, Sweep2, EdgeSrf, NetworkSrf and others.

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Thanks for your reply! I know of these other options and have used them in the past as well. I was particularly interested in why loft isn’t working in this case. Why does it give this surface? How should I define my curves to prevent this?

Loft works by connecting corresponding points on the input curves. Loft has no understanding of the user’s intentions, and does not appear to use the shape of the curves directly in determining the corresponding points between input curves.

If the “Do not simpliy” option is used then Loft appears to use the parameterization of the input curves to determine the corresponding points.

Selecting the “Rebuild” option in Loft appears to cause the input curves to be rebuilt for use in the Loft command similar or identical to the method used by the Rebuilt command. The parameterization then appears to be similar to the distance along the curve. This may improve and/or simplify the results in some cases, but in general the surface will not exactly match the input curve.

Selecting the “Refit” option in Loft appears to cause the input curves to be rebuilt for use in the Loft command similar or identical to the method used by the RebuildCrvNonuniform command. The result is then influenced by the curvature of the input curves. This may improve and/or simplify the results in some cases, but in general the surface will not exactly match the input curve.

Other options in Loft also influence the shape of the resulting surface.

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