opengl 让一个方框不被遮挡

本质上，就是让mesh曲面透明。

关键代码如下

glDepthMask(GL_FALSE);
glDrawArrays(GL_TRIANGLES, 36, 6);
glDepthMask(GL_TRUE);

详细代码如下：

    ///////////
    glColor3f(1.0,0.0,0.0);
    glDepthMask(GL_FALSE);
    
    glBegin(GL_TRIANGLES);
    for (fm = ((MainWindow*) win)->mesh.face.begin(); fm != ((MainWindow*) win)->mesh.face.end(); ++fm)
    {
        
        glNormal(fm->cN());
        glVertex(fm->V(0)->P());
        glVertex(fm->V(1)->P());
        glVertex(fm->V(2)->P());
        
    }
    glEnd();
    
    glDepthMask(GL_TRUE);
    //////////
    
    
    ////////////
    glColor3f(0.0,1.0,0.0);
    glLineWidth(8);
    glBegin( GL_LINES);
    
    glVertex3f(0.5,-0.5,0.5);
    glVertex3f(0.5,0.5,0.5);
    glEnd();
    
    ////////////