gluNurbsCurve

NAME

gluNurbsCurve -- define the shape of a NURBS curve

C SPECIFICATION

void gluNurbsCurve(GLUnurbsObj *nobj,
                   GLint nknots,
                   GLfloat *knot,
                   GLint stride,
                   GLfloat *ctlarray,
                   GLint order,
                   GLenum type)

PARAMETERS

nobj: Specifies the NURBS object (created with gluNewNurbsRenderer).
nknots: Specifies the number of knots in knot. nknots equals the number of control points plus the order.
knot: Specifies an array of nknots nondecreasing knot values.
stride: Specifies the offset (as a number of single-precision floating-point values) between successive curve control points.
ctlarray: 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 gluBeginCurve / gluEndCurve 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.