gluNurbsCurve

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.