matplotlib
diff --git a/‎lib/mpl_toolkits/mplot3d/art3d.py
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+1Lines changed: 1 addition & 0 deletions b/‎lib/mpl_toolkits/mplot3d/art3d.py
Copy file name to clipboardExpand all lines: lib/mpl_toolkits/mplot3d/art3d.py
+1Lines changed: 1 addition & 0 deletions
diff --git a/‎lib/mpl_toolkits/mplot3d/tests/test_art3d.py
Copy file name to clipboardExpand all lines: lib/mpl_toolkits/mplot3d/tests/test_art3d.py
+16-1Lines changed: 16 additions & 1 deletion b/‎lib/mpl_toolkits/mplot3d/tests/test_art3d.py
Copy file name to clipboardExpand all lines: lib/mpl_toolkits/mplot3d/tests/test_art3d.py
+16-1Lines changed: 16 additions & 1 deletion
@@ -1382,6 +1382,7 @@ def _generate_normals(polygons):
         v2 = np.empty((len(polygons), 3))
         for poly_i, ps in enumerate(polygons):
             n = len(ps)
+            ps = np.asarray(ps)
             i1, i2, i3 = 0, n//3, 2*n//3
             v1[poly_i, :] = ps[i1, :] - ps[i2, :]
             v2[poly_i, :] = ps[i2, :] - ps[i3, :]
 
@@ -3,7 +3,11 @@
 import matplotlib.pyplot as plt
 
 from matplotlib.backend_bases import MouseEvent
-from mpl_toolkits.mplot3d.art3d import Line3DCollection, _all_points_on_plane
+from mpl_toolkits.mplot3d.art3d import (
+    Line3DCollection,
+    Poly3DCollection,
+    _all_points_on_plane,
+)
 
 
 def test_scatter_3d_projection_conservation():
@@ -85,3 +89,14 @@ def test_all_points_on_plane():
     # All points lie on a plane
     points = np.array([[0, 0, 0], [0, 1, 0], [1, 0, 0], [1, 1, 0], [1, 2, 0]])
     assert _all_points_on_plane(*points.T)
+
+
+def test_generate_normals():
+    # Smoke test for https://github.com/matplotlib/matplotlib/issues/29156
+    vertices = ((0, 0, 0), (0, 5, 0), (5, 5, 0), (5, 0, 0))
+    shape = Poly3DCollection([vertices], edgecolors='r', shade=True)
+
+    fig = plt.figure()
+    ax = fig.add_subplot(projection='3d')
+    ax.add_collection3d(shape)
+    plt.draw()