GLUNURBSSURFACE() MachTen Programmer’s Manual GLUNURBSSURFACE()

NAME
gluNurbsSurface - define the shape of a NURBS surface

C SPECIFICATION
void gluNurbsSurface( GLUnurbs* nurb,
GLint sKnotCount,
GLfloat* sKnots,
GLint tKnotCount,
GLfloat* tKnots,
GLint sStride,
GLint tStride,
GLfloat* control,
GLint sOrder,
GLint tOrder,
GLenum type )

delim $$

PARAMETERS
nurb Specifies the NURBS object (created with
gluNewNurbsRenderer).

sKnotCount Specifies the number of knots in the paramet-
ric u direction.

sKnots Specifies an array of sKnotCount nondecreasing
knot values in the parametric u direction.

tKnotCount Specifies the number of knots in the paramet-
ric v direction.

tKnots Specifies an array of tKnotCount nondecreasing
knot values in the parametric v direction.

sStride Specifies the offset (as a number of single-
precision floating point values) between suc-
cessive control points in the parametric u
direction in control.

tStride Specifies the offset (in single-precision
floating-point values) between successive con-
trol points in the parametric v direction in
control.

control Specifies an array containing control points
for the NURBS surface. The offsets between
successive control points in the parametric u
and v directions are given by sStride and
tStride.

sOrder Specifies the order of the NURBS surface in
the parametric u direction. The order is one
more than the degree, hence a surface that is
cubic in u has a u order of 4.

tOrder Specifies the order of the NURBS surface in
the parametric v direction. The order is one
more than the degree, hence a surface that is
cubic in v has a v order of 4.

type Specifies type of the surface. type can be any
of the valid two-dimensional evaluator types
(such as GL_MAP2_VERTEX_3 or GL_MAP2_COLOR_4).

DESCRIPTION
Use gluNurbsSurface within a NURBS (Non-Uniform Rational
B-Spline) surface definition to describe the shape of a
NURBS surface (before any trimming). To mark the beginning
of a NURBS surface definition, use the gluBeginSurface
command. To mark the end of a NURBS surface definition,
use the gluEndSurface command. Call gluNurbsSurface within
a NURBS surface definition only.

Positional, texture, and color coordinates are associated
with a surface by presenting each as a separate gluNurb-
sSurface between a gluBeginSurface/gluEndSurface pair. No
more than one call to gluNurbsSurface for each of color,
position, and texture data can be made within a single
gluBeginSurface/gluEndSurface pair. Exactly one call must
be made to describe the position of the surface (a type of
GL_MAP2_VERTEX_3 or GL_MAP2_VERTEX_4).

A NURBS surface can be trimmed by using the commands
gluNurbsCurve and gluPwlCurve between calls to gluBe-
ginTrim and gluEndTrim.

Note that a gluNurbsSurface with sKnotCount knots in the u
direction and tKnotCount knots in the v direction with
orders sOrder and tOrder must have (sKnotCount - sOrder)
$times$ (tKnotCount - tOrder) control points.

EXAMPLE
The following commands render a textured NURBS surface
with normals; the texture coordinates and normals are also
NURBS surfaces:

gluBeginSurface(nobj);
gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);
gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);
gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4); gluEnd-
Surface(nobj);

SEE ALSO
gluBeginSurface, gluBeginTrim, gluNewNurbsRenderer,
gluNurbsCurve, gluPwlCurve

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