Navigation:  Hull Design > Corner Wrap

 

One of the characteristics of NURBS surfaces is that they fundamentally have four corners and four edges. As they are applied to hull design, these four edges usually correspond to the sheer line, the stem, the bottom profile, and the transom edge. The corners are the intersections of these four edges. Generally, the corners are discontinuities, with the exception of the stem-bottom profile corner (forefoot). Here, it's usually the case that a smooth transition is desired, with at least slope continuity, but preferably with curvature continuity (which requires a surface that is cubic in both the U and V directions).

 

Note: The Corner Wrap command requires that the surface have the same degree in both directions.

 

Orca3D provides a function to precisely place the corner control point to smoothly wrap one edge  to another, with slope and curvature (if the surface is cubic or higher degree) continuity. The next figure shows an Orca control polygon:

A closer look at the forefoot shows the control point that is the corner of the surface:

To demonstrate the function, the corner control point has been moved, deliberately creating a discontinuity in the joint between the stem and the bottom profile:

To re-create the smooth transition, select the Corner Wrap command from the Orca3D > Hull Design menu. The first prompt asks which surface the corner wrap should be applied to, and the second prompt allows you to select which of the four corners should be smoothly wrapped:

By clicking on any corner of the surface, its corresponding Corner will toggle between "No" and "Yes." Once you have selected the desired corner(s), hit Enter to complete the command. The corner control point will now be precisely located to create continuity at that corner.

If your surface is cubic (degree 3) in both directions, the corner will have curvature continuity. If it is quadratic (degree 2), it will have slope continuity.