GLUNURBSCURVE(3G)

NAME
gluNurbsCurve - define the shape of a NURBS curve

C SPECIFICATION

void gluNurbsCurve(GLUnurbs* nurb, GLint knotCount, GLfloat * knots, GLint stride, GLfloat * control, GLint order, GLenum type);

PARAMETERS

nurb
    Specifies the NURBS object (created with gluNewNurbsRenderer()).

knotCount
    Specifies the number of knots in knots. knotCount equals the number of control points plus the order.

knots
    Specifies an array of knotCount nondecreasing knot values.

stride
    Specifies the offset (as a number of single-precision floating-point values) between successive curve control points.

control
    Specifies a pointer to an array of control points. The coordinates must agree with type, specified below.

order
    Specifies the order of the NURBS curve. order equals degree + 1, hence a cubic curve has an order of 4.

type
    Specifies the type of the curve. If this curve is defined within a gluBeginCurve()/gluEndCurve() pair, then the type can be any of the valid one-dimensional evaluator types (such as GLU_MAP1_VERTEX_3 or GLU_MAP1_COLOR_4). Between a gluBeginTrim()/gluEndTrim() pair, the only valid types are GLU_MAP1_TRIM_2 and GLU_MAP1_TRIM_3.

DESCRIPTION

Use gluNurbsCurve to describe a NURBS curve.

When gluNurbsCurve appears between a gluBeginCurve()/gluEndCurve() pair, it is used to describe a curve to be rendered. Positional, texture, and color coordinates are associated by presenting each as a separate gluNurbsCurve between a gluBeginCurve()/gluEndCurve() pair. No more than one call to gluNurbsCurve for each of color, position, and texture data can be made within a single gluBeginCurve()/gluEndCurve() pair. Exactly one call must be made to describe the position of the curve (a type of GLU_MAP1_VERTEX_3 or GLU_MAP1_VERTEX_4).

When gluNurbsCurve appears between a gluBeginTrim()/gluEndTrim() pair, it is used to describe a trimming curve on a NURBS surface. If type is GLU_MAP1_TRIM_2, then it describes a curve in two-dimensional (u and v) parameter space. If it is GLU_MAP1_TRIM_3, then it describes a curve in two-dimensional homogeneous (u, v, and w) parameter space. See the gluBeginTrim() reference page for more discussion about trimming curves.

EXAMPLE

The following commands render a textured NURBS curve with normals:

    gluBeginCurve(nobj);
       gluNurbsCurve(nobj, ..., GL_MAP1_TEXTURE_COORD_2);
       gluNurbsCurve(nobj, ..., GL_MAP1_NORMAL);
       gluNurbsCurve(nobj, ..., GL_MAP1_VERTEX_4);
    gluEndCurve(nobj);

NOTES

To define trim curves that stitch well, use gluPwlCurve().

SEE ALSO

gluBeginCurve(), gluBeginTrim(), gluNewNurbsRenderer(), 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/.