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_C_ Original Code. The Original Code is: OpenGL Sample Implementation,
_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
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_C_ Additional Notice Provisions: The application programming interfaces
_C_ established by SGI in conjunction with the Original Code are The
_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
_C_ Window System(R) (Version 1.3), released October 19, 1998. This software
_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation
_C_ published by SGI, but has not been independently verified as being
_C_ compliant with the OpenGL(R) version 1.2.1 Specification.
_C_
_C_ $Date: 2004/03/14 08:29:09 $ $Revision: 1.1.1.4 $
_C_ The first character in this file must be an '_'!
_C_ Anything on a line after _C_ is ignored
_define(_filters,eqn)_C_
_C_      eqn is automatically replaced with neqn for nroff
_header(BeginCurve, delimit a NURBS curve definition)
_names(BeginCurve)
_names(EndCurve,,noheader)
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1)
Specifies the NURBS object (created with _cmnd(NewNurbsRenderer)).
.SH DESCRIPTION
Use _cmnd(BeginCurve) to mark the beginning of a NURBS 
curve definition.
After 
calling _cmnd(BeginCurve), make one or more calls to
_cmnd(NurbsCurve) to define the attributes of the curve.
Exactly one of the calls to _cmnd(NurbsCurve) must have
a curve type of _const(MAP1_VERTEX_3) or _const(MAP1_VERTEX_4).
To mark the end of the NURBS curve definition, call _cmnd(EndCurve).
.P
GL evaluators are used to render the NURBS curve as a series of line
segments.
Evaluator state is preserved during rendering
with _glcmnd(PushAttrib)(_const(EVAL_BIT)) and 
_glcmnd(PopAttrib)().  
See the _glcmnd(PushAttrib) reference page for details on exactly what state
these calls preserve.
.SH EXAMPLE
The following commands render a textured NURBS curve with normals;
texture coordinates and normals are also specified as NURBS curves:
.sp
.Ex
gluBeginCurve(nobj);
   gluNurbsCurve(nobj, ..., GL_MAP1_TEXTURE_COORD_2);
   gluNurbsCurve(nobj, ..., GL_MAP1_NORMAL);
   gluNurbsCurve(nobj, ..., GL_MAP1_VERTEX_4);
gluEndCurve(nobj);
.Ee
.SH SEE ALSO
_cmnd(BeginSurface), _cmnd(BeginTrim), _cmnd(NewNurbsRenderer), 
_cmnd(NurbsCurve), 
_glcmnd(PopAttrib), _glcmnd(PushAttrib)