gluNurbsSurface - define the shape of a NURBS surface
void gluNurbsSurface( GLUnurbsObj *nobj, GLint uknot_count, GLfloat *uknot, GLint vknot_count, GLfloat *vknot, GLint u_stride, GLint v_stride, GLfloat *ctlarray, GLint uorder, GLint vorder, GLenum type )
nobj Specifies the NURBS object (created with gluNewNurbsRenderer). uknot_count Specifies the number of knots in the parametric u direction. uknot Specifies an array of uknot_count nondecreasing knot values in the parametric u direction. vknot_count Specifies the number of knots in the parametric v direction. vknot Specifies an array of vknot_count nondecreasing knot values in the parametric v direction. u_stride Specifies the offset (as a number of single-precision floating point values) between successive control points in the parametric u direction in ctlarray. v_stride Specifies the offset (in single-precision floating-point values) between successive control points in the parametric v direction in ctlarray. ctlarray 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 u_stride and v_stride. uorder 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. vorder 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).
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 uknot_count knots in the u direction and vknot_count knots in the v direction with orders uorder and vorder must have (uknot_count - uorder) x (vknot_count - vorder) control points.
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);
gluBeginSurface, gluBeginTrim, gluNewNurbsRenderer, gluNurbsCurve, gluPwlCurve
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Last Edited: Mon, May 22, 1995