How to create a collar NURBS surface along any boundary of a mesh, or curve-on-mesh.

The collar surface is fitted to the mesh along the selected curve (edge or otherwise) and provides continuity information along that curve, allowing you to build additional geometry from it.

A curve-on-mesh results from projecting a curve on a mesh, or intersecting meshes.

See Project curves on meshes.

See Project curves normal to meshes.

See Create curves at mesh intersections.

Create a collar surface against a mesh

1. Choose Mesh > Mesh Collar.
2. Select a mesh.

   All the mesh boundaries, and curves-on-mesh, are highlighted in green.

   
3. Click at two locations along one of the green curves to specify a segment.

   A collar surface is built along the curve, covering the shortest distance between the two points.

   
4. If the collar surface runs in the wrong direction, press the Reverse button.
   Note

   On a curve-on-mesh, the Reverse button flips the collar to the other side of the curve, instead of changing its direction.

5. Click on more points, if necessary, to refine the shape of the collar. Each new point creates an extra segment (span).

   The collar is fitted to the mesh along its entire width, as well as along the selected boundary or curve-on-mesh.

   Collar surfaces are degree 5 in the U direction, and degree 3 in the V direction, by default.

   
6. Optionally, you can do the following:
   • Move the points (shown as green locators) along the curve. The collar surface updates interactively.
   • Remove a point by holding and clicking the point. (Periodic collars need at least one point, and non-periodic collars need at least two.)
   • Change properties of the collar such as degree, width, number of spans per segment, and whether or not the collar is periodic (closed) through the option box. The collar surface updates interactively.
   • Turn on Show Surface Deviation and/or Show Deviation Map to get information on the deviation between the mesh and the collar. (See Control Options.)
     
7. Press the Next button to create another collar surface without having to re-invoke the tool.
   

You can then use NURBS modeling tools on the edge of the collar surfaces to build additional surfaces against the mesh.

If you turn on Create History, you can use Object Edit > Query Edit or the History View window and select the collar to re-enter the tool and modify the option values and input points. However, changing the geometry of the mesh boundary or curve-on-mesh used to build the collar will destroy the collar history.