opengl gluNurbsCurve函数问题

[wjxkkxx]

theNurb=gluNewNurbsRenderer();
gluNurbsProperty(theNurb,GLU_SAMPLING_TOLERANCE,10.0);
gluNurbsProperty(theNurb,GLU_DISPLAY_MODE,GLU_FILL);
GLfloat ctrlpoints[9][3] = {{4,0,0},{2.828,2.828,0},{0,4,0},{-2.828,2.828,0},
{-4,0,0},{-2.828,-2.828,0},{0,-4,0},{2.828,-2.828,0},
{4,0,0}};
GLfloat knots[12] = {1,2,3,4,5,6,7,8,9,10,11,12};
gluBeginCurve(theNurb);
gluNurbsCurve(theNurb,12,knots,3,&ctrlpoints[0][0],3,GL_MAP1_VERTEX_3);
gluEndCurve(theNurb);
我想绘制一个闭合的圆但上述代码绘制的圆有一个缺口如何解决？

[libralibra]

在x-y平面内画一个圆心在[Center_x,Center_y]半径为R的圆

glBegin(GL_LINE_STRIP);
   for(int angle = 0; angle <= 360; angle++)
   {
      GLfloat px = Center_x + R*cos(angle/180.0 *pi);
      GLfloat py = Center_y + R*sin(angle/180.0 *pi);
      glVertex2f(px,py);
   }
   glEnd();

[libralibra]

你用nurbs画圆也行,但是nurbs曲线过首尾控制点的充要条件是
头尾节点必须重复: 次数+1次
如果你画的是3次nurbs曲线
节点必须为[0,0,0,0,....1,1,1,1]的形式,才能画出来过2端控制点的曲线