openGL画直线、圆、椭圆(5)

/* so this could be omitted: */

drawcircle(250,250,100);

/* and flush that buffer to the screen */

glFlush();

}

void display3() //画圆

{

glClear(GL_COLOR_BUFFER_BIT); /*clear the window */

/*----------------------------------------*/

/* viewport stuff */

/*----------------------------------------*/

/* set up a viewport in the screen window */

/* args to glViewport are left, bottom, width, height */

glViewport(0, 0, 500, 500);

/* NB: default viewport has same coords as in myinit, */

/* so this could be omitted: */

drawEllipse(250,250,60,40);

/* and flush that buffer to the screen */

glFlush();

}

int main(int argc, char** argv)

{

/* Standard GLUT initialization */

glutInit(&argc,argv);

glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); /* default, not needed */ glutInitWindowSize(500,500); /* 500 x 500 pixel window */

glutInitWindowPosition(0,0); /* place window top left on display */

cout<<"************************************************"<<endl; cout<<"**** 请选择如下操作: *****"<<endl; cout<<"**** 1.用DDA画线 *****"<<endl; cout<<"**** 2.用Bresenham算法画圆 *****"<<endl; cout<<"**** 3.用Bresenham算法画椭圆 *****"<<endl; cout<<"************************************************"<<endl; cout<<"请选择如下操作:"; int choice;