mixing 2d and 3d in opengl (using pyglet)

Question

I am trying to mix 2d and 3d in opengl in pyglet, i.e. draw a 3d scene then switch to orthographic projection and draw stuff over the top. I draw the 3d stuff, push the projection matrix to the stack, do a glOrtho projection matrix, draw the 2d stuff, then pop the previous matrix off the stack. The 3d stuff draws fine but for some reason the 2d part isn't drawing at all, even on its own. Here's the code:

class Window(pyglet.window.Window):

    # resolution
    width, height = 1024, 786

    def __init__(self, width, height):

        # initialise window
        super(Window, self).__init__(width, height)

        # set title
        self.set_caption("OpenGL Doss")

        # call update() at 30fps
        pyglet.clock.schedule_interval(self.update, 1 / 30.0)

        glEnable(GL_TEXTURE_2D)         # enable textures
        glShadeModel(GL_SMOOTH)         # smooth shading of polygons
        glClearColor(0.0, 0.0, 0.0, 0.0)

        glClearDepth(1.0)

        glDepthFunc(GL_LEQUAL)           
        glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST)   # make stuff look nice

        self.world = World()            # initialise world

        self.label = pyglet.text.Label('Hello, world',
                          font_name='Times New Roman',
                          font_size=20,
                          width=10, height=10)

    def on_resize(self, width, height):
        print 'on resize'
        if height == 0:
            height = 1
        glViewport(0, 0, width, height) # specify viewport

        # load perspective projection matrix
        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        gluPerspective(45, 1.0 * width / height, 0.1, 100.0)
        #glLoadIdentity()

    def on_draw(self):
        self.set3d()

        # draw 3d stuff
        self.world.draw()

        self.set2d()

        # draw 2d stuff
        self.draw2d()

        self.unSet2d()

    def update(self, dt):
        "called at set interval during runtime"
        #maze = self.world.maze
        maze_platform = self.world.maze_platform

        pacman = maze_platform.maze.pacman

        maze_platform.update()

        # send it world pointer
        pacman.update(self.world)



    def on_key_press(self, symbol, modifiers):
        control.press(symbol, modifiers)

    def on_key_release(self, symbol, modifiers):
        control.release(symbol, modifiers)

    def set3d(self):
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
        glEnable(GL_DEPTH_TEST)         # enable depth testing
        # reset modelview matrix
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()

    def set2d(self):

        glDisable(GL_DEPTH_TEST)
        # store the projection matrix to restore later
        glMatrixMode(GL_PROJECTION)
        glPushMatrix()

        # load orthographic projection matrix
        glLoadIdentity()
        #glOrtho(0, float(self.width),0, float(self.height), 0, 1)
        far = 8192
        glOrtho(-self.width / 2., self.width / 2., -self.height / 2., self.height / 2., 0, far)

        # reset modelview
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()

        #glClear(GL_COLOR_BUFFER_BIT)



    def unSet2d(self):

        # load back the projection matrix saved before
        glMatrixMode(GL_PROJECTION)
        glPopMatrix() 

    def draw2d(self):
        z=-6
        n=100
        glTranslatef(0, 0.0, -z)


        glBegin(GL_TRIANGLES)
        glVertex3f(0.0, n, 0.0)
        glVertex3f(-n, -n, 0)
        glVertex3f(n, -n, 0)
        glEnd()


def main():
    window = Window(Window.width, Window.height)
    pyglet.app.run()
    print 'framerate:', pyglet.clock.get_fps(), '(error checking = %s)' % pyglet.options['debug_gl']

if __name__ == '__main__': main()
    #command = 'main()'
    #cProfile.run(command)

Answer 1

I would recommend that you fully reset the modelview and projection matrices on each render, and then don't use push/pop when you go from 3d to 2d.

However, I suspect that you are using bad coordinates so the scene is drawing outside the clip planes. In partciular I am a tad suspicious of putting the near clipping plane at zero. Normally 2d elements are drawn with z=0.

Try putting the near clip-plane at -1.

I'm also a bit unsure why you're calling glTranslatef(0, 0.0, -z) in draw2d, I wouldn't bother.

Answer 2

In draw2d() try glDisable(GL_TEXTURE_2D) and glColor3ub(255,255,255) before drawing your triangle.

Make sure to re-glEnable(GL_TEXTURE_2D) before calling world.draw() again if it uses textured geometry.