Glu.NurbsCurve (gb.opengl.glu)
Static Sub NurbsCurve ( Nurb As GluNurb, KnotCount As Integer, Knots As Single[], Stride As Integer, Control As Single[], Order As Integer, Type As Integer )
Define the shape of a NURBS curve.
Parameters
- nurb
-
Specifies the NURBS object (created with Glu.NewNurbsRenderer).
- 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
Glu.BeginCurve/Glu.EndCurve 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 Glu.BeginTrim/Glu.EndTrim pair,
the only valid types are Glu.MAP1_TRIM_2 and Glu.MAP1_TRIM_3.
Description
Use
Glu.NurbsCurve to describe a NURBS curve.
When
Glu.NurbsCurve appears between a Glu.BeginCurve/Glu.EndCurve pair, it is
used to describe a curve to be rendered.
Positional, texture, and color coordinates are associated
by presenting each as a separate
Glu.NurbsCurve between a
Glu.BeginCurve/Glu.EndCurve pair. No more than
one call to
Glu.NurbsCurve for each of color, position, and texture
data can be made within a single Glu.BeginCurve/Glu.EndCurve
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
Glu.NurbsCurve appears between a Glu.BeginTrim/Glu.EndTrim 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 Glu.BeginTrim 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 Glu.PwlCurve.
See also
Glu.BeginCurve,
Glu.BeginTrim,
Glu.PwlCurve