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      "source": [
        "%gui qt"
      ]
    },
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      "metadata": {},
      "source": [
        "\n# Show post-processing using a FrameBuffer\n"
      ]
    },
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      "execution_count": null,
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      "source": [
        "import numpy as np\nfrom vispy import app\n\nfrom vispy.geometry import create_cube\nfrom vispy.util.transforms import perspective, translate, rotate\nfrom vispy.gloo import (Program, VertexBuffer, IndexBuffer, Texture2D, clear,\n                        FrameBuffer, RenderBuffer, set_viewport, set_state)\n\n\ncube_vertex = \"\"\"\nuniform mat4 model;\nuniform mat4 view;\nuniform mat4 projection;\nattribute vec3 position;\nattribute vec2 texcoord;\nattribute vec3 normal;  // not used in this example\nattribute vec4 color;  // not used in this example\nvarying vec2 v_texcoord;\nvoid main()\n{\n    gl_Position = projection * view * model * vec4(position,1.0);\n    v_texcoord = texcoord;\n}\n\"\"\"\n\ncube_fragment = \"\"\"\nuniform sampler2D texture;\nvarying vec2 v_texcoord;\nvoid main()\n{\n    float r = texture2D(texture, v_texcoord).r;\n    gl_FragColor = vec4(r,r,r,1);\n}\n\"\"\"\n\nquad_vertex = \"\"\"\nattribute vec2 position;\nattribute vec2 texcoord;\nvarying vec2 v_texcoord;\nvoid main()\n{\n    gl_Position = vec4(position, 0.0, 1.0);\n    v_texcoord = texcoord;\n}\n\"\"\"\n\nquad_fragment = \"\"\"\nuniform sampler2D texture;\nvarying vec2 v_texcoord;\nvoid main()\n{\n    vec2 d = 5.0 * vec2(sin(v_texcoord.y*50.0),0)/512.0;\n\n    // Inverse video\n    if( v_texcoord.x > 0.5 ) {\n        gl_FragColor.rgb = 1.0-texture2D(texture, v_texcoord+d).rgb;\n    } else {\n        gl_FragColor = texture2D(texture, v_texcoord);\n    }\n}\n\"\"\"\n\n\ndef checkerboard(grid_num=8, grid_size=32):\n    row_even = grid_num // 2 * [0, 1]\n    row_odd = grid_num // 2 * [1, 0]\n    Z = np.row_stack(grid_num // 2 * (row_even, row_odd)).astype(np.uint8)\n    return 255 * Z.repeat(grid_size, axis=0).repeat(grid_size, axis=1)\n\n\nclass Canvas(app.Canvas):\n\n    def __init__(self):\n        app.Canvas.__init__(self, title='Framebuffer post-processing',\n                            keys='interactive', size=(512, 512))\n\n        # Build cube data\n        # --------------------------------------\n        vertices, indices, _ = create_cube()\n        vertices = VertexBuffer(vertices)\n        self.indices = IndexBuffer(indices)\n\n        # Build program\n        # --------------------------------------\n        view = translate((0, 0, -7))\n        self.phi, self.theta = 60, 20\n        model = rotate(self.theta, (0, 0, 1)).dot(rotate(self.phi, (0, 1, 0)))\n\n        self.cube = Program(cube_vertex, cube_fragment)\n        self.cube.bind(vertices)\n        self.cube[\"texture\"] = checkerboard()\n        self.cube[\"texture\"].interpolation = 'linear'\n        self.cube['model'] = model\n        self.cube['view'] = view\n\n        color = Texture2D((512, 512, 3), interpolation='linear')\n        self.framebuffer = FrameBuffer(color, RenderBuffer((512, 512)))\n\n        self.quad = Program(quad_vertex, quad_fragment, count=4)\n        self.quad['texcoord'] = [(0, 0), (0, 1), (1, 0), (1, 1)]\n        self.quad['position'] = [(-1, -1), (-1, +1), (+1, -1), (+1, +1)]\n        self.quad['texture'] = color\n\n        # OpenGL and Timer initalization\n        # --------------------------------------\n        set_state(clear_color=(.3, .3, .35, 1), depth_test=True)\n        self.timer = app.Timer('auto', connect=self.on_timer, start=True)\n        self._set_projection(self.physical_size)\n\n        self.show()\n\n    def on_draw(self, event):\n        with self.framebuffer:\n            set_viewport(0, 0, 512, 512)\n            clear(color=True, depth=True)\n            set_state(depth_test=True)\n            self.cube.draw('triangles', self.indices)\n        set_viewport(0, 0, *self.physical_size)\n        clear(color=True)\n        set_state(depth_test=False)\n        self.quad.draw('triangle_strip')\n\n    def on_resize(self, event):\n        self._set_projection(event.physical_size)\n\n    def _set_projection(self, size):\n        width, height = size\n        set_viewport(0, 0, width, height)\n        projection = perspective(30.0, width / float(height), 2.0, 10.0)\n        self.cube['projection'] = projection\n\n    def on_timer(self, event):\n        self.theta += .5\n        self.phi += .5\n        model = rotate(self.theta, (0, 0, 1)).dot(rotate(self.phi, (0, 1, 0)))\n        self.cube['model'] = model\n        self.update()\n\n\nif __name__ == '__main__':\n    canvas = Canvas()\n    app.run()"
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