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        "%gui qt"
      ]
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      "source": [
        "\n# Volume Rendering\n\nExample volume rendering\n\nControls:\n\n* 1  - toggle camera between first person (fly), regular 3D (turntable) and\n       arcball\n* 2  - toggle between volume rendering methods\n* 3  - toggle between stent-CT / brain-MRI image\n* 4  - toggle between colormaps\n* 5  - toggle between interpolation methods\n* 0  - reset cameras\n* [] - decrease/increase isosurface threshold\n\nWith fly camera:\n\n* WASD or arrow keys - move around\n* SPACE - brake\n* FC - move up-down\n* IJKL or mouse - look around\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
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      "source": [
        "from itertools import cycle\n\nimport numpy as np\n\nfrom vispy import app, scene, io\nfrom vispy.color import get_colormaps, BaseColormap\nfrom vispy.visuals.transforms import STTransform\n\n# Read volume\nvol1 = np.load(io.load_data_file('volume/stent.npz'))['arr_0']\nvol2 = np.load(io.load_data_file('brain/mri.npz'))['data']\nvol2 = np.flipud(np.rollaxis(vol2, 1))\n\n# Prepare canvas\ncanvas = scene.SceneCanvas(keys='interactive', size=(800, 600), show=True)\ncanvas.measure_fps()\n\n# Set up a viewbox to display the image with interactive pan/zoom\nview = canvas.central_widget.add_view()\n\n# Create the volume visuals, only one is visible\nvolume1 = scene.visuals.Volume(vol1, parent=view.scene, threshold=0.225)\nvolume1.transform = scene.STTransform(translate=(64, 64, 0))\nvolume2 = scene.visuals.Volume(vol2, parent=view.scene, threshold=0.2)\nvolume2.visible = False\n\n# Create three cameras (Fly, Turntable and Arcball)\nfov = 60.\ncam1 = scene.cameras.FlyCamera(parent=view.scene, fov=fov, name='Fly')\ncam2 = scene.cameras.TurntableCamera(parent=view.scene, fov=fov,\n                                     name='Turntable')\ncam3 = scene.cameras.ArcballCamera(parent=view.scene, fov=fov, name='Arcball')\nview.camera = cam2  # Select turntable at first\n\n# Create an XYZAxis visual\naxis = scene.visuals.XYZAxis(parent=view)\ns = STTransform(translate=(50, 50), scale=(50, 50, 50, 1))\naffine = s.as_matrix()\naxis.transform = affine\n\n\n# create colormaps that work well for translucent and additive volume rendering\nclass TransFire(BaseColormap):\n    glsl_map = \"\"\"\n    vec4 translucent_fire(float t) {\n        return vec4(pow(t, 0.5), t, t*t, max(0, t*1.05 - 0.05));\n    }\n    \"\"\"\n\n\nclass TransGrays(BaseColormap):\n    glsl_map = \"\"\"\n    vec4 translucent_grays(float t) {\n        return vec4(t, t, t, t*0.05);\n    }\n    \"\"\"\n\n# Setup colormap iterators\nopaque_cmaps = cycle(get_colormaps())\ntranslucent_cmaps = cycle([TransFire(), TransGrays()])\nopaque_cmap = next(opaque_cmaps)\ntranslucent_cmap = next(translucent_cmaps)\n\ninterp_methods = cycle(volume1.interpolation_methods)\ninterp = next(interp_methods)\n\n\n# Implement axis connection with cam2\n@canvas.events.mouse_move.connect\ndef on_mouse_move(event):\n    if event.button == 1 and event.is_dragging:\n        axis.transform.reset()\n\n        axis.transform.rotate(cam2.roll, (0, 0, 1))\n        axis.transform.rotate(cam2.elevation, (1, 0, 0))\n        axis.transform.rotate(cam2.azimuth, (0, 1, 0))\n\n        axis.transform.scale((50, 50, 0.001))\n        axis.transform.translate((50., 50.))\n        axis.update()\n\n\n# Implement key presses\n@canvas.events.key_press.connect\ndef on_key_press(event):\n    global opaque_cmap, translucent_cmap\n    if event.text == '1':\n        cam_toggle = {cam1: cam2, cam2: cam3, cam3: cam1}\n        view.camera = cam_toggle.get(view.camera, cam2)\n        print(view.camera.name + ' camera')\n        if view.camera is cam2:\n            axis.visible = True\n        else:\n            axis.visible = False\n    elif event.text == '2':\n        methods = ['mip', 'translucent', 'iso', 'additive']\n        method = methods[(methods.index(volume1.method) + 1) % 4]\n        print(\"Volume render method: %s\" % method)\n        cmap = opaque_cmap if method in ['mip', 'iso'] else translucent_cmap\n        volume1.method = method\n        volume1.cmap = cmap\n        volume2.method = method\n        volume2.cmap = cmap\n    elif event.text == '3':\n        volume1.visible = not volume1.visible\n        volume2.visible = not volume1.visible\n    elif event.text == '4':\n        if volume1.method in ['mip', 'iso']:\n            cmap = opaque_cmap = next(opaque_cmaps)\n        else:\n            cmap = translucent_cmap = next(translucent_cmaps)\n        volume1.cmap = cmap\n        volume2.cmap = cmap\n    elif event.text == '5':\n        interp = next(interp_methods)\n        volume1.interpolation = interp\n        volume2.interpolation = interp\n        print(f\"Interpolation method: {interp}\")\n    elif event.text == '0':\n        cam1.set_range()\n        cam3.set_range()\n    elif event.text != '' and event.text in '[]':\n        s = -0.025 if event.text == '[' else 0.025\n        volume1.threshold += s\n        volume2.threshold += s\n        th = volume1.threshold if volume1.visible else volume2.threshold\n        print(\"Isosurface threshold: %0.3f\" % th)\n\n# for testing performance\n# @canvas.connect\n# def on_draw(ev):\n# canvas.update()\n\nif __name__ == '__main__':\n    print(__doc__)\n    app.run()"
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