Using PyOpenGL with GLU and PyGame.

I have a VAO with a VBO and IBO behind it that provide the vertex and index data for the faces. In addition I have a simple vertex and fragment shader. Things render find.

However, I’d like to add ImGUI to my application. So I did the following:

def main():
    width = 800
    height = 800

    display = (width, height)

    pygame.init()
    pygame.display.set_caption('OpenGL VAO with pygame')
    pygame.display.set_mode(display, pygame.DOUBLEBUF | pygame.OPENGL | pygame.RESIZABLE)
    pygame.display.gl_set_attribute(pygame.GL_CONTEXT_MAJOR_VERSION, 4)
    pygame.display.gl_set_attribute(pygame.GL_CONTEXT_MINOR_VERSION, 1)
    pygame.display.gl_set_attribute(pygame.GL_CONTEXT_PROFILE_MASK, pygame.GL_CONTEXT_PROFILE_CORE)

    imgui.create_context()
    impl = PygameRenderer()
    io = imgui.get_io()
    #io.set_WantCaptureMouse(True)
    io.display_size = width, height

    init()

    clock = pygame.time.Clock()
    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
            impl.process_event(event)

        render(time=clock, imgui_impl=impl)

        pygame.display.flip()
        pygame.time.wait(10)

if __name__ == '__main__':
    main()

There are two important functions here:

• init() – loads and compiles the shaders into a program, creates the VBO and IBO and binds them
• render() – clears depth and color buffers, creates and binds the VAO, turns on the shaders, renders the contents of the VAO etc.

The render() function looks similar to this:

def render(time, imgui_impl):
    glClearColor(0.0, 0.0, 0.0, 0.0)
    glClearDepth(1.0)
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    
    glUseProgram(program)
    glBindVertexArray(vao)
    
    fElapsedTime = pygame.time.get_ticks() / 1000.0
    for func in g_instanceList:
        transformMatrix = func(fElapsedTime)
        
        glUniformMatrix4fv(modelToCameraMatrixUnif, 1, GL_FALSE, transformMatrix.transpose())
        glDrawElements(GL_TRIANGLES, len(indexData), GL_UNSIGNED_SHORT, None)
    
    glBindVertexArray(0)
    glUseProgram(0)

    imgui.new_frame()
    imgui.begin('Controls', True)
    changed, strings = imgui.input_text('Path to OBJ', '...', imgui.INPUT_TEXT_READ_ONLY)
    imgui.same_line()
    if imgui.button('Load'):
        print('Loading', strings)
    imgui.end()
    imgui.end_frame()
    imgui.render()
    print(imgui.get_draw_data().valid)
    imgui_impl.render(imgui.get_draw_data())

My problem is that ImGUI doesn’t show at all. I checked the validity of the ImGui draw data object

imgui.get_draw_data().valid

and it returns True.

How should I handle the ImGUI data? I do turn of the program (shaders) so the only issue I am thinking of is the VAO and that is somehow affects the rendering of the UI.