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)`;

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 GLU_MAP2_VERTEX_3 or GLU_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 GLU_MAP2_VERTEX_3 or GLU_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);