Kivy:如何在给定的布局中渲染3D模型

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.widget import Widget
from kivy.graphics import RenderContext, Color, PushMatrix, PopMatrix, Rotate, Translate, Mesh
from kivy.clock import Clock
from kivy.core.window import Window
from kivy.resources import resource_find

class ModelWidget(Widget):
    def __init__(self, **kwargs):
        super(ModelWidget, self).__init__(**kwargs)
        self.canvas = RenderContext(use_parent_projection=True)
        self.mesh = None

    def on_size(self, *args):
        self.canvas.size = self.size

    def on_pos(self, *args):
        self.canvas.pos = self.pos

    def on_mesh(self, instance, value):
        self.canvas.clear()
        with self.canvas:
            Color(1, 1, 1, 1)
            PushMatrix()
            self.mesh = Mesh(vertices=value['vertices'], indices=value['indices'], fmt=value['fmt'], mode=value['mode'])
            PopMatrix()

class MainLayout(FloatLayout):
    def __init__(self, **kwargs):
        super(MainLayout, self).__init__(**kwargs)
        self.model_widget = ModelWidget()
        self.add_widget(self.model_widget)

class MyApp(App):
    def build(self):
        layout = MainLayout()
        return layout

if __name__ == '__main__':
    MyApp().run()