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，截图

我想要这样的期望输出

Answer 1

GL_TRIANGLE_FAN primitiv 的第一个点始终保持固定（参见三角形基元）。 只需在“内部”点之一启动GL_TRIANGLE_FAN primitiv：

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();

Answer 2

您正在创建一个三角形扇形，但将其中心顶点（初始顶点）设置为 0,6,0。

您可能想要更改几何形状，以便您的中心顶点位于原点（为了对称）。 正如@Rabbid76 所示，它还可以将第一个顶点向下移动到底部。