c++ - 如何使用 glut openGL 绘制 4 角星

Question

我想在 C++ 中使用 GLUT 和 openGL 绘制一个 4pointed star。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();

问题是形状直接从0,6变成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

第1点GL_TRIANGLE_FAN primitiv 始终保持固定(参见 Triangle primitives )。只需启动 GL_TRIANGLE_FAN原始点位于“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();