GLUNURBSCURVE

Section: Misc. Reference Manual Pages (3G)
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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 )

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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.