gluNurbsSurface()

NAME

gluNurbsSurface − define the shape of a NURBS surface

SYNOPSIS

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 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.

typeSpecifies 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);

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