gluNurbsSurface

NAME

gluNurbsSurface -- define the shape of a NURBS surface

C SPECIFICATION

void gluNurbsSurface(GLUnurbsObj *nobj,
                     GLint sknot_count,
                     GLfloat *sknot,
                     GLint tknot_count,
                     GLfloat *tknot,
                     GLint s_stride,
                     GLint t_stride,
                     GLfloat *ctlarray,
                     GLint sorder,
                     GLint torder,
                     GLenum type)

PARAMETERS

nobj: Specifies the NURBS object (created with gluNewNurbsRenderer).
sknot_count: Specifies the number of knots in the parametric s direction.
sknot: Specifies an array of sknot_count nondecreasing knot values in the parametric s direction.
tknot_count: Specifies the number of knots in the parametric t direction.
tknot: Specifies an array of tknot_count nondecreasing knot values in the parametric t direction.
s_stride: Specifies the offset (as a number of single-precision floating point values) between successive control points in the parametric s direction in ctlarray.
t_stride: Specifies the offset (in single-precision floating-point values) between successive control points in the parametric t direction in ctlarray.
ctlarray: Specifies an array containing control points for the NURBS surface. The offsets between successive control points in the parametric s and t directions are given by s_stride and t_stride.
sorder: Specifies the order of the NURBS surface in the parametric s direction. The order is one more than the degree, hence a surface that is cubic in s has a sorder of 4.
torder: Specifies the order of the NURBS surface in the parametric t direction. The order is one more than the degree, hence a surface that is cubic in t has a torder 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 sknot_count knots in the s direction and tknot_count knots in the t direction with orders sorder and torder must have (sknot_count - sorder) * (tknot_count - torder) control points.

EXAMPLE

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