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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 )
 

delim $$

PARAMETERS

nurb

Specifies the NURBS object (created with gluNewNurbsRenderer).

sKnotCount

Specifies the number of knots in the parametric u direction.

sKnots

Specifies an array of sKnotCount nondecreasing knot values in the parametric u direction.

tKnotCount

Specifies the number of knots in the parametric v direction.

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) $times$ (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);

SEE ALSO

gluBeginSurface(3G), gluBeginTrim(3G), gluNewNurbsRenderer(3G), gluNurbsCurve(3G), gluPwlCurve(3G)