1991-2006 Silicon Graphics, Inc.
gluNurbsSurface 3G
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);

## See Also

gluBeginSurface, gluBeginTrim, gluNewNurbsRenderer, gluNurbsCurve, gluPwlCurve

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.