There are also the degree and parameterization of the NURB curve. Did you try that (uniform vs non-uniform)?
On Tue, Jun 18, 2013 at 4:49 PM, Ponthieux, Joseph G. (LARC-E1A)[LITES] < [email protected]> wrote: > Yeah, tried that, except when I set the multiplicity to 3 it apparently > converts the curve to Bezier control. Kinda defeats the purpose as I could > just create the curve a Bezier from the get go if I wanted that.**** > > ** ** > > --**** > > 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.**** > > ** ** > > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *Daniel Brassard > *Sent:* Tuesday, June 18, 2013 4:40 PM > *To:* [email protected] > *Subject:* Re: bezier -> nurbs**** > > ** ** > > 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.**** > > **** > > ** ** > > ** ** >
