3D场景上的2D覆盖不起作用

Question

I am attempting to create a 2D overlay over a 3D scene! I have tried all the solutions I can find on GameDev and StackOverflow, however they have not seemed to work!

My current code:

static void ready3D()
{
    glViewport(0, 0, Display.getWidth(),Display.getHeight());
    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();
    GLU.gluPerspective(45, (float) Display.getWidth()/Display.getHeight(), 0.1f, 5000.0f);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glDepthFunc(GL_LEQUAL);
    glEnable(GL_DEPTH_TEST);
}

static void ready2D()
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    GLU.gluOrtho2D(0.0f, Display.getWidth(), Display.getHeight(), 0.0f);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.375f, 0.375f, 0.0f);

    glDisable(GL_DEPTH_TEST);
}

And,

glPushMatrix();
    //Overlay start - This is in my render method BTW.
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    ready2D();

    glBegin(GL_QUADS);
    glColor3f(1, 1, 1);
    glVertex2f(0, 0); // bottom-left
            glVertex2f(0, 1); // top-left
            glVertex2f(1, 1); // top-right
            glVertex2f(1, 0); // bottom-right
    glEnd();

    glPopMatrix();
    ready3D();

However the 2D box thing that I am trying to draw does not draw! Obviously I eventually hope to have complicated objects/icons on an overlay, but first things first.

The 3D world still draws totally fine.

Is anyone able to tell me what I am doing wrong?

Answer 1

The order of the vertices in the 2D quad look a bit suspicious to me, if I'm reading that rightly it's going: bottom-left, top-right, bottom-right, top-left, which results in a sort of cross rather than a quad.

Try this:

glVertex2f(0, 0); // bottom-left
glVertex2f(0, 1); // top-left
glVertex2f(1, 1); // top-right
glVertex2f(1, 0); // bottom-right

Note the clockwise ordering which I believe OpenGL is expecting by default for front-facing quads.