2013

Table Of Contents
Create NURBS Surfaces
Create NURBS surfaces by enabling NURBS creation and using many of the
same commands used to create procedural surfaces. You can also convert
existing procedural surfaces into NURBS surfaces.
NURBS (Non-Uniform Rational B-Splines) surfaces are part of the suite of 3D
modeling objects that AutoCAD offers (in addition to 3D solids, procedural
surfaces, and meshes).
NURBS surfaces are based on Bezier curves or splines. Therefore, settings such
as degree, fit points, control vertices, weights, and knot parameterization are
important in defining a NURBS surface or curve. AutoCAD splines are
optimized to create NURBS surfaces allowing you to control many of these
options (see SPLINE and SPLINEDIT). The illustration below shows the control
vertices that display when you select a NURBS surface or spline.
Two Methods for Creating NURBS Surfaces
There are two ways to create NURBS surfaces:
SURFACEMODELINGMODE system variable - Use any of the surface
creation commands while this system variable is set to 1.
CONVTONURBS command - Convert any existing surfaces with this
command.
It is important to plan ahead with NURBS modeling, since NURBS surfaces
cannot be converted back into procedural surfaces.
See also:
Create Solids and Surfaces from Lines and Curves (page 342)
378 | Chapter 8 Work with 3D Models