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.
Procedure
To create a NURBS surface
by lofting
Click Surface
tabCreate
panelNURBS
CreationAt the Command prompt,
enter convtonurbs (if
it is not already enabled).
Click Surface
tabCreate
panelLoft.At the Command prompt,
enter loft.
Select the cross section
profiles and press Enter. Select them in the
order in which you want the new 3D object to pass through them.
After
the loft operation, the original objects are deleted or retained, depending
on the setting of the DELOBJ system variable.
To convert a solid into
a NURBS surface
Click Surface
tabControl
Vertices panelConvert
to NURBS.At the Command prompt,
enter convtonurbs.
Select a solid and press Enter.
The object is converted into multiple NURBS surfaces (each face
becomes a separate surface).
NoteTo display the control
vertices, click Surface
tabControl
Vertices panelShow
CV.At the Command prompt,
enter cvshow
To convert a mesh object
into a NURBS surface
Click Mesh tabConvert MeshConvert
to Surface.At the Command prompt,
enter convtosurface
Select a mesh object and press Enter.
The object is converted
to a procedural surface.
ClickSurface
tabCreate
panelNURBS
Creation.At the Command prompt,
enter convtonurbs.
The object is converted
to a NURBS surface.
NoteTo display the control
vertices, click Surface
tabControl
Vertices panelShow
CV.At the Command prompt,
enter cvshow
