正四边形,正五边形,正六边形,……,直到正 n 边形,当 n 越大时,这个图形就越接近圆,当 n 大到一定程度后,人眼将无法把它跟真正的圆相区别
#include <GL/glut.h>
#include <math.h>
const int n = 20;
const GLfloat R = 0.5f;
const GLfloat Pi = 3.1415926536f;
void myDisplay(void) {
int i;
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POLYGON);
for(i=0;i<n;++i)
glVertex2f(R*cos(2*Pi/n*i),R*sin(2*Pi/n*i));
glEnd();
glFlush();
}
int main(int argc, char *argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
glutInitWindowPosition(100, 100);
glutInitWindowSize(400, 400);
glutCreateWindow("绘制点线面");
glutDisplayFunc(&myDisplay);
glutMainLoop();
return 0;
}