gluBeginSurface

王朝百科·作者佚名 2010-03-06

宽屏版字体: 小|中|大|超大

NAME

gluBeginSurface, gluEndSurface - delimit a NURBS surface definition

C SPECIFICATION

void gluBeginSurface( GLUnurbsObj *nobj )

void gluEndSurface( GLUnurbsObj *nobj )

PARAMETERS

nobj ? Specifies the NURBS object (created with gluNewNurbsRenderer).

DESCRIPTION

Use gluBeginSurface to mark the beginning of a NURBS surface definition. After calling gluBeginSurface, make one or more calls to gluNurbsSurface to define the attributes of the surface. Exactly one of these calls to gluNurbsSurface must have a surface type of GL_MAP2_VERTEX_3 or GL_MAP2_VERTEX_4. To mark the end of the NURBS surface definition, call gluEndSurface.

Trimming of NURBS surfaces is supported with gluBeginTrim, gluPwlCurve, gluNurbsCurve, and gluEndTrim. Refer to the gluBeginTrim reference page for details.

OpenGL evaluators are used to render the NURBS surface as a set of polygons. Evaluator state is preserved during rendering with glPushAttrib(GL_EVAL_BIT) and glPopAttrib(). See the "glPushAttrib" reference page for details on exactly what state these calls preserve.

EXAMPLE

The following commands render a textured NURBS surface with normals; the texture coordinates and normals are also described as NURBS surfaces:

gluBeginSurface(nobj);

gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);

gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);

gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4);

gluEndSurface(nobj);