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    {
      "cell_type": "code",
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      "source": [
        "%matplotlib inline"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "# Line Widget {#line_widget_example}\n\nThe line widget can be enabled and disabled by the\n`pyvista.Plotter.add_line_widget`{.interpreted-text role=\"func\"} and\n`pyvista.Plotter.clear_line_widgets`{.interpreted-text role=\"func\"}\nmethods respectively. Unfortunately, PyVista does not have any helper\nmethods to utilize this widget, so it is necessary to pass a custom\ncallback method.\n\nOne particularly fun example is to use the line widget to create a\nsource for the `pyvista.DataSetFilters.streamlines`{.interpreted-text\nrole=\"func\"} filter. Again note the use of the `name` argument in\n`add_mesh`.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "import numpy as np\n\nimport pyvista as pv\nfrom pyvista import examples\n\npv.set_plot_theme('document')\n\nmesh = examples.download_kitchen()\nfurniture = examples.download_kitchen(split=True)\n\narr = np.linalg.norm(mesh['velocity'], axis=1)\nclim = [arr.min(), arr.max()]"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "p = pv.Plotter()\np.add_mesh(furniture, name='furniture', color=True)\np.add_mesh(mesh.outline(), color='black')\np.add_axes()\n\n\ndef simulate(pointa, pointb):\n    streamlines = mesh.streamlines(\n        n_points=10,\n        max_steps=100,\n        pointa=pointa,\n        pointb=pointb,\n        integration_direction='forward',\n    )\n    p.add_mesh(streamlines, name='streamlines', line_width=5, render_lines_as_tubes=True, clim=clim)\n\n\np.add_line_widget(callback=simulate, use_vertices=True)\np.show()"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "And here is a screen capture of a user interacting with this\n\n![image](../../images/gifs/line-widget-streamlines.gif)\n"
      ]
    }
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