Enable spelling linter for Markdown, reStructuredText and IPython notebooks

Summary: Enable spelling linter for Markdown, reStructuredText and IPython notebooks under `fbcode/vision/fair`. Apply suggested fixes.

Reviewed By: ppwwyyxx

Differential Revision: D20495298

fbshipit-source-id: 95310c7b51f9fa68ba2aa34ecc39a874da36a75c

docs/tutorials/utils/camera_visualization.py

@@ -0,0 +1,70 @@
+# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
+
+import matplotlib.pyplot as plt
+import torch
+from mpl_toolkits.mplot3d import Axes3D  # noqa: F401 unused import
+
+
+def get_camera_wireframe(scale: float = 0.3):
+    """
+    Returns a wireframe of a 3D line-plot of a camera symbol.
+    """
+    a = 0.5 * torch.tensor([-2, 1.5, 4])
+    b = 0.5 * torch.tensor([2, 1.5, 4])
+    c = 0.5 * torch.tensor([-2, -1.5, 4])
+    d = 0.5 * torch.tensor([2, -1.5, 4])
+    C = torch.zeros(3)
+    F = torch.tensor([0, 0, 3])
+    camera_points = [a, b, d, c, a, C, b, d, C, c, C, F]
+    lines = torch.stack([x.float() for x in camera_points]) * scale
+    return lines
+
+
+def plot_cameras(ax, cameras, color: str = "blue"):
+    """
+    Plots a set of `cameras` objects into the maplotlib axis `ax` with
+    color `color`.
+    """
+    cam_wires_canonical = get_camera_wireframe().cuda()[None]
+    cam_trans = cameras.get_world_to_view_transform().inverse()
+    cam_wires_trans = cam_trans.transform_points(cam_wires_canonical)
+    plot_handles = []
+    for wire in cam_wires_trans:
+        # the Z and Y axes are flipped intentionally here!
+        x_, z_, y_ = wire.detach().cpu().numpy().T.astype(float)
+        (h,) = ax.plot(x_, y_, z_, color=color, linewidth=0.3)
+        plot_handles.append(h)
+    return plot_handles
+
+
+def plot_camera_scene(cameras, cameras_gt, status: str):
+    """
+    Plots a set of predicted cameras `cameras` and their corresponding
+    ground truth locations `cameras_gt`. The plot is named with
+    a string passed inside the `status` argument.
+    """
+    fig = plt.figure()
+    ax = fig.gca(projection="3d")
+    ax.clear()
+    ax.set_title(status)
+    handle_cam = plot_cameras(ax, cameras, color="#FF7D1E")
+    handle_cam_gt = plot_cameras(ax, cameras_gt, color="#812CE5")
+    plot_radius = 3
+    ax.set_xlim3d([-plot_radius, plot_radius])
+    ax.set_ylim3d([3 - plot_radius, 3 + plot_radius])
+    ax.set_zlim3d([-plot_radius, plot_radius])
+    ax.set_xlabel("x")
+    ax.set_ylabel("z")
+    ax.set_zlabel("y")
+    labels_handles = {
+        "Estimated cameras": handle_cam[0],
+        "GT cameras": handle_cam_gt[0],
+    }
+    ax.legend(
+        labels_handles.values(),
+        labels_handles.keys(),
+        loc="upper center",
+        bbox_to_anchor=(0.5, 0),
+    )
+    plt.show()
+    return fig