c++ - 如何使用 glut openGL 绘制一个 4 尖星

Question

我想在 C++ 中使用 GLUT 和 openGL 绘制一个四角星。这是我的代码

glBegin(GL_TRIANGLE_FAN);
    glVertex3f(0.0f,6.0f,0.0f);
    glVertex3f(1.0f,4.0f,0.0f);
    glVertex3f(3.0f,3.0f,0.0f);
    glVertex3f(1.0f,2.0f,0.0f);
    glVertex3f(0.0f,0.0f,0.0f);
    glVertex3f(-1.0f,2.0f,0.0f);
    glVertex3f(-3.0f,3.0f,0.0f);
    glVertex3f(-1.0f,4.0f,0.0f);

glEnd();

问题是形状从 0,6 直接变为 3,3
谁能帮我解决这个问题，
screenshot
我想要这样的东西
desired output

Answer 1

GL_TRIANGLE_FAN的第1点primitiv 始终保持固定(参见 Triangle primitives)。刚开始GL_TRIANGLE_FAN primitiv 在“内部”点之一:

glBegin(GL_TRIANGLE_FAN);
    
    glVertex3f(1.0f,4.0f,0.0f);
    glVertex3f(3.0f,3.0f,0.0f);
    glVertex3f(1.0f,2.0f,0.0f);
    glVertex3f(0.0f,0.0f,0.0f);
    glVertex3f(-1.0f,2.0f,0.0f);
    glVertex3f(-3.0f,3.0f,0.0f);
    glVertex3f(-1.0f,4.0f,0.0f);

    glVertex3f(0.0f,6.0f,0.0f);

glEnd();