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## 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 )

eqn not supported

## 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 GL_MAP1_VERTEX_3 or GL_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 GL_MAP1_VERTEX_3 or GL_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 which stitch well, use gluPwlCurve.

## See Also

gluBeginCurve(3G) , gluBeginTrim(3G) , gluNewNurbsRenderer(3G) , gluPwlCurve(3G)

Table of Contents

- Name
- C Specification
- Parameters
- Description
- Example
- Notes
- See Also