GLUNURBSSURFACE

Section: Misc. Reference Manual Pages (3G)
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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 )

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PARAMETERS

nurb: Specifies the NURBS object (created with gluNewNurbsRenderer).
sKnotCount: Specifies the number of knots in the parametric u direction.
sKnots: Specifies an array of sKnotCount nondecreasing knot values in the parametric u direction.
tKnotCount: Specifies the number of knots in the parametric 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 successive control points in the parametric u direction in control.
tStride: Specifies the offset (in single-precision floating-point values) between successive control 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 gluNurbsSurface 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 gluBeginTrim 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); gluEndSurface(nobj);