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      "source": [
        "%gui qt"
      ]
    },
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      "metadata": {},
      "source": [
        "\n# Show a rotating cube with lighting\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
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      "source": [
        "import numpy as np\n\nfrom vispy import gloo, app\nfrom vispy.gloo import Program, VertexBuffer, IndexBuffer\nfrom vispy.util.transforms import perspective, translate, rotate\nfrom vispy.geometry import create_cube\n\n\nvertex = \"\"\"\nuniform mat4 u_model;\nuniform mat4 u_view;\nuniform mat4 u_projection;\nuniform vec4 u_color;\n\nattribute vec3 position;\nattribute vec2 texcoord;\nattribute vec3 normal;\nattribute vec4 color;\n\nvarying vec3 v_position;\nvarying vec3 v_normal;\nvarying vec4 v_color;\n\nvoid main()\n{\n    v_normal = normal;\n    v_position = position;\n    v_color = color * u_color;\n    gl_Position = u_projection * u_view * u_model * vec4(position,1.0);\n}\n\"\"\"\n\nfragment = \"\"\"\nuniform mat4 u_model;\nuniform mat4 u_view;\nuniform mat4 u_normal;\n\nuniform vec3 u_light_intensity;\nuniform vec3 u_light_position;\n\nvarying vec3 v_position;\nvarying vec3 v_normal;\nvarying vec4 v_color;\n\nvoid main()\n{\n    // Calculate normal in world coordinates\n    vec3 normal = normalize(u_normal * vec4(v_normal,1.0)).xyz;\n\n    // Calculate the location of this fragment (pixel) in world coordinates\n    vec3 position = vec3(u_view*u_model * vec4(v_position, 1));\n\n    // Calculate the vector from this pixels surface to the light source\n    vec3 surfaceToLight = u_light_position - position;\n\n    // Calculate the cosine of the angle of incidence (brightness)\n    float brightness = dot(normal, surfaceToLight) /\n                      (length(surfaceToLight) * length(normal));\n    brightness = max(min(brightness,1.0),0.0);\n\n    // Calculate final color of the pixel, based on:\n    // 1. The angle of incidence: brightness\n    // 2. The color/intensities of the light: light.intensities\n    // 3. The texture and texture coord: texture(tex, fragTexCoord)\n\n    gl_FragColor = v_color * brightness * vec4(u_light_intensity, 1);\n}\n\"\"\"\n\n\nclass Canvas(app.Canvas):\n    def __init__(self):\n        app.Canvas.__init__(self, size=(512, 512), title='Lighted cube',\n                            keys='interactive')\n        self.timer = app.Timer('auto', self.on_timer)\n\n        # Build cube data\n        V, F, outline = create_cube()\n        vertices = VertexBuffer(V)\n        self.faces = IndexBuffer(F)\n        self.outline = IndexBuffer(outline)\n\n        # Build view, model, projection & normal\n        # --------------------------------------\n        self.view = translate((0, 0, -5))\n        model = np.eye(4, dtype=np.float32)\n        normal = np.array(np.matrix(np.dot(self.view, model)).I.T)\n\n        # Build program\n        # --------------------------------------\n        self.program = Program(vertex, fragment)\n        self.program.bind(vertices)\n        self.program[\"u_light_position\"] = 2, 2, 2\n        self.program[\"u_light_intensity\"] = 1, 1, 1\n        self.program[\"u_model\"] = model\n        self.program[\"u_view\"] = self.view\n        self.program[\"u_normal\"] = normal\n        self.phi, self.theta = 0, 0\n\n        self.activate_zoom()\n\n        # OpenGL initialization\n        # --------------------------------------\n        gloo.set_state(clear_color=(0.30, 0.30, 0.35, 1.00), depth_test=True,\n                       polygon_offset=(1, 1),\n                       blend_func=('src_alpha', 'one_minus_src_alpha'),\n                       line_width=0.75)\n        self.timer.start()\n\n        self.show()\n\n    def on_draw(self, event):\n        gloo.clear(color=True, depth=True)\n        # program.draw(gl.GL_TRIANGLES, indices)\n\n        # Filled cube\n        gloo.set_state(blend=False, depth_test=True, polygon_offset_fill=True)\n        self.program['u_color'] = 1, 1, 1, 1\n        self.program.draw('triangles', self.faces)\n\n        # Outlined cube\n        gloo.set_state(polygon_offset_fill=False, blend=True, depth_mask=False)\n        self.program['u_color'] = 0, 0, 0, 1\n        self.program.draw('lines', self.outline)\n        gloo.set_state(depth_mask=True)\n\n    def on_resize(self, event):\n        self.activate_zoom()\n\n    def activate_zoom(self):\n        gloo.set_viewport(0, 0, *self.physical_size)\n        projection = perspective(45.0, self.size[0] / float(self.size[1]),\n                                 2.0, 10.0)\n        self.program['u_projection'] = projection\n\n    def on_timer(self, event):\n        self.theta += .5\n        self.phi += .5\n        model = np.dot(rotate(self.theta, (0, 0, 1)),\n                       rotate(self.phi, (0, 1, 0)))\n        normal = np.linalg.inv(np.dot(self.view, model)).T\n        self.program['u_model'] = model\n        self.program['u_normal'] = normal\n        self.update()\n\nif __name__ == '__main__':\n    c = Canvas()\n    app.run()"
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