René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Doc]: Gallery example showing 3D slice planes","articleBody":"@timhoffm suggested in https://github.com/matplotlib/matplotlib/issues/3919#issuecomment-2116282472 that we make a gallery example for plotting X Y Z planar slices through a volume.\r\n\r\nHis result and its code:\r\n\r\n![331397449-09310bdd-35b6-4587-b2bf-f0046d2f0b16](https://github.com/matplotlib/matplotlib/assets/14363975/f7dc6efc-aa18-4d0c-a40a-91254fbfd3f6)\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\ndef plot_quadrants(ax, array, fixed_coord, cmap):\r\n    \"\"\"For a given 3d *array* plot a plane with *fixed_coord*, using four individual quadrants.\"\"\"\r\n    nx, ny, nz = array.shape\r\n    index = {\r\n        'x': (nx//2, slice(None), slice(None)),\r\n        'y': (slice(None), ny//2, slice(None)),\r\n        'z': (slice(None), slice(None), nz//2),\r\n    }[fixed_coord]\r\n    plane_data = array[index]\r\n\r\n    n0, n1 = plane_data.shape\r\n    quadrants = [\r\n        plane_data[:n0//2, :n1//2],\r\n        plane_data[:n0//2, n1//2:],\r\n        plane_data[n0//2:, :n1//2],\r\n        plane_data[n0//2:, n1//2:]\r\n    ]\r\n\r\n    min_val = array.min()\r\n    max_val = array.max()\r\n    \r\n    cmap = plt.get_cmap(cmap)\r\n    \r\n    for i, quadrant in enumerate(quadrants):\r\n        facecolors = cmap((quadrant - min_val) / (max_val-min_val))\r\n        if fixed_coord == 'x':\r\n            Y, Z = np.mgrid[0:ny//2, 0:nz//2]\r\n            X = nx//2 * np.ones_like(Y)\r\n            Y_offset = (i // 2) * ny//2\r\n            Z_offset = (i % 2) * nz//2\r\n            ax.plot_surface(X, Y + Y_offset, Z + Z_offset, rstride=1, cstride=1, facecolors=facecolors, shade=False)\r\n        elif fixed_coord == 'y':\r\n            X, Z = np.mgrid[0:nx//2, 0:nz//2]\r\n            Y = ny//2 * np.ones_like(X)\r\n            X_offset = (i // 2) * nx//2\r\n            Z_offset = (i % 2) * nz//2\r\n            ax.plot_surface(X + X_offset, Y, Z + Z_offset, rstride=1, cstride=1, facecolors=facecolors, shade=False)\r\n        elif fixed_coord == 'z':\r\n            X, Y = np.mgrid[0:nx//2, 0:ny//2]\r\n            Z = nz//2 * np.ones_like(X)\r\n            X_offset = (i // 2) * nx//2\r\n            Y_offset = (i % 2) * ny//2\r\n            ax.plot_surface(X + X_offset, Y + Y_offset, Z, rstride=1, cstride=1, facecolors=facecolors, shade=False)\r\n\r\n\r\ndef figure_3D_array_slices(array, cmap=None):\r\n    \"\"\"Plot a 3d array using three intersecting centered planes.\"\"\"\r\n    fig = plt.figure()\r\n    ax = fig.add_subplot(projection='3d')\r\n    ax.set_box_aspect(array.shape)\r\n    plot_quadrants(ax, array, 'x', cmap=cmap)\r\n    plot_quadrants(ax, array, 'y', cmap=cmap)\r\n    plot_quadrants(ax, array, 'z', cmap=cmap)\r\n    return fig, ax\r\n\r\n\r\nnx, ny, nz = 70, 100, 50\r\nr_square = (np.mgrid[-1:1:1j*nx, -1:1:1j*ny, -1:1:1j*nz]**2).sum(0)\r\n\r\nfigure_3D_array_slices(r_square, cmap='viridis_r')\r\nplt.show()\r\n```\r\n","author":{"url":"https://github.com/scottshambaugh","@type":"Person","name":"scottshambaugh"},"datePublished":"2024-05-16T23:02:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/28239/matplotlib/issues/28239"}