GL_QUADS吸引，而不是recangle

Question

凹五边形我使用这个代码来生成矩形

glBegin(GL_QUADS); 
glColor3f(0,0,0); 
glVertex2f(-0.9,-0.9); 
glVertex2f(-0.9,+0.9); 
glVertex2f(+0.9,-0.9); 
glVertex2f(+0.9,+0.9); 
glEnd(); 

Draws this

我的窗口设置与此代码：

glutInit(&argc, argv); 
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); 
glutInitWindowSize(600,600); 
glutInitWindowPosition(0,0); 
glutCreateWindow("Atari Breakout!"); 
glClearColor(0,1,0,1); 
glOrtho(-1.0f, +1.0f, -1.0f,+1.0f,1,1); 
glutDisplayFunc(display); 
glutIdleFunc(display); 

glutMainLoop(); 

Answer 1

顺序你的顶点就像字母N，它在原始中间翻转绕组。您必须按照一致的排列顺序提交顶点。