OpenGL画曲线

void CShape::drawCurve() {    glClear(GL_COLOR_BUFFER_BIT);    glBegin(GL_LINES);    glPointSize(10.0f);    glColor3f(0.0f, 1.0f, 0.0f);    glVertex2f(-1.0f, 0.0f);//动态绘制x坐标    glVertex2f(beginXpoint += 0.01f, 0.0f);    glVertex2f(0.0f,1.0f);//动态绘制y坐标    glVertex2f(0.0f,beginYpoint -= 0.01f);    glEnd();    //GL_LINE_STRIP:不闭合折线    //GL_LINES:多组双顶点线段    //GL_LINE_LOOP : 首尾坐标相连,闭合折线    glBegin(GL_LINE_STRIP);    glColor3f(1.0f, 0.0f, 0.0f);    for(float fValue = -1.0f; fValue <= beginPoint_.x; fValue += 0.0001f) {        glVertex2f(fValue, fValue * fValue);    }    beginPoint_.x += 0.01f;    glEnd();    glFlush();    glutSwapBuffers();}

void CShape::init() {    beginPoint_.x = -1.0f;    beginPoint_.y = 1.0f;    endPoint_.x = 1.0f;    endPoint_.y = 1.0f;    beginXpoint = -1.0f;    beginYpoint = 1.0f;    glClearColor(0.0f, 1.0f, 0, 1.0f);    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DOUBLE);    glutInitWindowPosition(100, 100);    glutInitWindowSize(400, 300);    glutCreateWindow("**");    glMatrixMode(GL_TEXTURE);    glLoadIdentity(); //Move to the Center    //gluOrtho2D(-0.0f, 0.0f, -0.0f, 0.0f);    glOrtho(-0.0f, 0.0f, -0.0f, 0.0f, 1.0f, 1.0f);    glEnable(GL_LINE_SMOOTH);    glEnable(GL_BLEND);    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);    glHint(GL_LINE_SMOOTH_HINT, GL_DONT_CARE);    //glLineWidth(1.0f);    glutDisplayFunc(&CShape::drawCurve);    glutIdleFunc(&CShape::displayDrawShape);    glutMainLoop();}