GLUNURBSSURFACE(3gl)
NAME
gluNurbsSurface - define the shape of a NURBS surface
C SPECIFICATION
- void gluNurbsSurface( GLUnurbs* nurb,
- GLint sKnotCount,
GLfloat* sKnots,
GLint tKnotCount,
GLfloat* tKnots,
GLint sStride,
GLint tStride,
GLfloat* control,
GLint sOrder,
GLint tOrder,
GLenum type )
PARAMETERS
- nurb Specifies the NURBS object (created with
- gluNewNurbsRenderer).
- sKnotCount Specifies the number of knots in the parametric u direc
- tion.
- sKnots Specifies an array of sKnotCount nondecreasing knot values
- in the parametric u direction.
- tKnotCount Specifies the number of knots in the parametric v direc
- tion.
- tKnots Specifies an array of tKnotCount nondecreasing knot values
- in the parametric v direction.
- sStride Specifies the offset (as a number of single-precision
- floating point values) between successive control points in the parametric u direction in control.
- tStride Specifies the offset (in single-precision floating-point
- values) between successive control points in the parametric v direction in control.
- control Specifies an array containing control points for the NURBS
- surface. The offsets between successive control points in the parametric u and v directions are given by sStride and tStride.
- sOrder Specifies the order of the NURBS surface in the parametric
- u direction. The order is one more than the degree, hence a surface that is cubic in u has a u order of 4.
- tOrder Specifies the order of the NURBS surface in the parametric
- v direction. The order is one more than the degree, hence a surface that is cubic in v has a v order of 4.
- type Specifies type of the surface. type can be any of the valid
- two-dimensional evaluator types (such as GL_MAP2_VERTEX_3 or GL_MAP2_COLOR_4).
DESCRIPTION
Use gluNurbsSurface within a NURBS (Non-Uniform Rational B-Spline) surface definition to describe the shape of a NURBS surface (before any
trimming). To mark the beginning of a NURBS surface definition, use the
gluBeginSurface command. To mark the end of a NURBS surface definition, use the gluEndSurface command. Call gluNurbsSurface within a
NURBS surface definition only.
Positional, texture, and color coordinates are associated with a surface by presenting each as a separate gluNurbsSurface between a gluBeginSurface/gluEndSurface pair. No more than one call to gluNurbsSurface for each of color, position, and texture data can be made within a single gluBeginSurface/gluEndSurface pair. Exactly one call must be made to describe the position of the surface (a type of GL_MAP2_VERTEX_3 or GL_MAP2_VERTEX_4).
A NURBS surface can be trimmed by using the commands gluNurbsCurve and gluPwlCurve between calls to gluBeginTrim and gluEndTrim.
Note that a gluNurbsSurface with sKnotCount knots in the u direction and tKnotCount knots in the v direction with orders sOrder and tOrder must have (sKnotCount - sOrder) x (tKnotCount - tOrder) control points.
EXAMPLE
The following commands render a textured NURBS surface with normals;
the texture coordinates and normals are also NURBS surfaces:
- gluBeginSurface(nobj);
- gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);
gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);
gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4); gluEndSurface(nobj);