Oops, reverse. >From the book
Multiplicity is a property of knots that refers to the number of control points associated to a knot. On a cubic curve, a knot can have a multiplicity of 1, 2, or 3. On a surface, each knot curve has two multiplicities: one in the U direction and one in V. All knots along a knot curve must have the same multiplicity in the corresponding direction. Knots with a multiplicity greater than 1 are sometimes called *multiknots*. Multiknots allow for greater control over the trace of the curve through the knot, at the expense of smoothness. - A knot with a multiplicity of 1 has C2 continuity (curvature). - A knot with multiplicity 2 has C1 continuity (tangency). - A knot with multiplicity 3 has C0 continuity (position) if the three control points are not lined up. It is like a Bézier point, with one control point exactly at the position of the knot on the curve and the other two control points acting like tangent handles. You can manipulate these knots on curves in a Bézier-like manner — see Using the Tweak Curve Tool<http://download.autodesk.com/global/docs/softimage2013/en_us/userguide/files/curves_DrawingandManipulatingCurves.htm#WS20FD922AA9DF2240AD94FFADCE73807F-002F> . On Tue, Jun 18, 2013 at 4:36 PM, Daniel Brassard <[email protected]>wrote: > Raise the knot to multiplicity 3 (similar to bezier) > > Lower the knots to 2 (curvature) first and second derivative continuity, > smoother curve. > Lower the knots to 1 (tangent) first derivative continuity, tangent > continuity > Lower the knots to 0 (linear), sharp turns, no continuity between knots > > > On Tue, Jun 18, 2013 at 4:08 PM, Ponthieux, Joseph G. (LARC-E1A)[LITES] < > [email protected]> wrote: > >> Its been so long since I’ve tried this in Soft I can’t remember…**** >> >> ** ** >> >> Is there any logic or formula that will allow you to replicate a Bezier >> Knot curve as a CV curve?**** >> >> ** ** >> >> I thought all you had to do was make sure the CVs on a Nurbs curve >> matched the handle points on a Bezier curve and they would align perfectly, >> but the continuity of the Bezier curves is slightly different than the >> Nurbs, almost as though the Bezier is a different degree than the Nurbs >> curve. Is that the case?**** >> >> ** ** >> >> Second, is it possible to convert a Bezier curve to a Nurbs CV curve and >> maintain continuity, bias, etc?**** >> >> ** ** >> >> --**** >> >> Joey Ponthieux**** >> >> LaRC Information Technology Enhanced Services (LITES)**** >> >> Mymic Technical Services**** >> >> NASA Langley Research Center**** >> >> __________________________________________________**** >> >> Opinions stated here-in are strictly those of the author and do not **** >> >> represent the opinions of NASA or any other party.**** >> >> ** ** >> > >
