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GLUNURBSSURFACE(3G) OpenGL Manual GLUNURBSSURFACE(3G)

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);

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/.

AUTHORS

opengl.org

04/12/2021 opengl.org