You can also add an additional curve over the closed loop to constrain and VCade
the patch surface.

When you create a patch surface, you can specify surface continuity and bulge magnitude.
If the SURFACEASSOCIATIVITY system variable is set to 1, associativity is maintained
between the patch surface and the originating edges or curves.

The following prompts are displayed.

Surface Edges

Selects individual surface edges and adds them to the selection set.

Chain

Selects contiguous edges of connected but separate surface objects.

Curves

Selects curves rather than edges.

Accept the patch surface

Creates a patch that spans the edges you selected.

Continuity

Measures how smoothly surfaces flow into each other. The default is G0. Select a value
or use the grip to change the continuity.

Bulge Magnitude

For best results, enter a value between 0 and 1 to set the roundness of the patch
surface edge where it meets the originating surface. The default is 0.5.

VCades

Uses additional VCade curves to shape the patch surface. VCade curves can be curves
or points.