gluBeginCurve example c c++ objc java

Name

gluBeginCurve — delimit a NURBS curve definition

C Specification

void gluBeginCurve( GLUnurbs* nurb);

C Specification

void gluEndCurve( GLUnurbs* nurb);

Parameters

nurb: Specifies the NURBS object (created with gluNewNurbsRenderer).

Description

Use gluBeginCurve to mark the beginning of a NURBS curve definition. After calling gluBeginCurve, make one or more calls to gluNurbsCurve to define the attributes of the curve. Exactly one of the calls to gluNurbsCurve must have a curve type of GLU_MAP1_VERTEX_3or GLU_MAP1_VERTEX_4. To mark the end of the NURBS curve definition, call gluEndCurve.
GL evaluators are used to render the NURBS curve as a series of line segments. Evaluator state is preserved during rendering with glPushAttrib(GLU_EVAL_BIT) and glPopAttrib(). See the glPushAttrib reference page for details on exactly what state these calls preserve.

Example of gluBeginCurve

The following commands render a textured NURBS curve with normals; texture coordinates and normals are also specified as NURBS curves:
<Example 1>

gluBeginCurve(nobj);
   gluNurbsCurve(nobj, ..., GL_MAP1_TEXTURE_COORD_2);
   gluNurbsCurve(nobj, ..., GL_MAP1_NORMAL);
   gluNurbsCurve(nobj, ..., GL_MAP1_VERTEX_4);
gluEndCurve(nobj);

<Example 2>

glColor3f(CS390_CURVE_COLOR);      /* select a drawing color     */
glLineWidth(2);                    /* select a line width        */
if(n >= 2) {                       /* draw curve only if n >= 2  */
    glShadeModel(GL_FLAT);         /* select a shading model     */
    glEnable(GL_MAP1_VERTEX_3);    /* activate mapping and do it */
    gluBeginCurve(theNurbs);       /* start NURBS curve drawing  */
    gluNurbsCurve(theNurbs,        /* draw a NURBS curve         */
                  m,               /* # of knots                 */
                  &knot_v[0],      /* knot vector                */
                  3,               /* u stride                   */
                  &points_v[0][0], /* control points array       */
                  p + 1,           /* order = degree + 1         */
                  GL_MAP1_VERTEX_3);    /* do it as here         */
    gluEndCurve(theNurbs);         /* end of NURBS curve drawing */
}

Example source code bank

Thursday, June 2, 2011