深度缓冲区不适用于Android，但适用于Linux（使用Kivy）

As Reto Koradi had suggested, I looked again even deeper into the Kivy documentation. I discovered Framebuffer (module kivy.graphics.fbo), which is an offscreen window, that acts like a Kivy Canvas. It (probably unlike Canvas) has with_depthbuffer parameter, which is set to False by default.

So the solution was to set with_depthbuffer = True in Framebuffer and then use the Framebuffer's rendered texture in Canvas in order to display it.

我不确定为什么这对于Android是必需的，但对于Linux不是必需的。还有一个更好的选择，它不包括创建（有时是无意义的）帧缓冲，但是这种方法至少在两个平台上都适用。

我修改了示例代码：

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.core.window import Window
from kivy.resources import resource_find
from kivy.graphics.transformation import Matrix
from kivy.graphics import *
from kivy.graphics.opengl import *
import random

class Root(Widget):
    def __init__(self, *larg, **kw):
        super(Root, self).__init__(*larg, **kw)     
        self.vertices = [[-1,-1, 0,    1,-1, 0,    1, 1, 0,   -1, 1, 0]]
        with self.canvas:
             self.fbo = Fbo(with_depthbuffer = True, size = Window.size)
             Rectangle(size=Window.size, texture=self.fbo.texture)

        kw['shader_file'] = 'shaders.glsl'
        shader_file = kw.pop('shader_file')   
        self.fbo.shader.source = resource_find(shader_file)
        with self.fbo:
            self.cb = Callback(self.setup_gl_context)
            PushMatrix()
            Translate(0, 0, -5)
            for i in xrange(10):
                Translate(.5, 0, -.5)
                self.render(self.vertices, (random.random(), random.random(), random.random()))
            PopMatrix()
            self.cb = Callback(self.reset_gl_context)

        asp = float(Window.width) / Window.height / 2.0
        proj = Matrix().view_clip(-asp, asp, -0.5, 0.5, 1, 100, 1)
        self.fbo['projection_mat'] = proj

    def setup_gl_context(self, *args):
        glEnable(GL_DEPTH_TEST)

    def reset_gl_context(self, *args):
        glDisable(GL_DEPTH_TEST)

    def render(self, vertices, color):
        for i in xrange(len(vertices)):
            ChangeState(Kd=color, Ka=color, Ks=(.3, .3, .3), Tr=1., Ns=1., intensity=1.)
            Mesh(vertices=vertices[i], indices=[0, 1, 2, 3, 0, 2], fmt=[('v_pos', 3, 'float')], mode='triangles')

class TestApp(App): 
    def build(self):
        return Root()

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