1991-2006 Silicon Graphics, Inc.
gluNurbsCurve 3G
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/.