Add early fail for get_normal_newell when the provided polygon is t…

…oo small (< 3)

cjio/geom_help.py

@@ -12,7 +12,7 @@
 try:
     import mapbox_earcut
 except ImportError as e:
-    MODULE_EARCUT_AVAILABLE = False    
+    MODULE_EARCUT_AVAILABLE = False
 
 def to_2d(p, n):
     #-- n must be normalised
@@ -24,7 +24,7 @@ def to_2d(p, n):
         x3 += np.array([1,2,3])
     x3 = x3 - np.dot(x3, n) * n
     # print(n, x3)
-    x3 /= math.sqrt((x3**2).sum())   # make x a unit vector    
+    x3 /= math.sqrt((x3**2).sum())   # make x a unit vector
     y3 = np.cross(n, x3)
     return (np.dot(p, x3), np.dot(p, y3))
 
@@ -39,14 +39,16 @@ def get_normal_newell(poly):
         ne = i + 1
         if (ne == len(poly)):
             ne = 0
+        if len(poly[i]) < 3 or len(poly[ne]) < 3:
+            return n, False
         n[0] += ( (poly[i][1] - poly[ne][1]) * (poly[i][2] + poly[ne][2]) )
         n[1] += ( (poly[i][2] - poly[ne][2]) * (poly[i][0] + poly[ne][0]) )
         n[2] += ( (poly[i][0] - poly[ne][0]) * (poly[i][1] + poly[ne][1]) )
-    
+
     if (n==np.array([0.0, 0.0, 0.0])).all():
         # print("one wrong")
         return (n, False)
-    n = n / math.sqrt(n[0]*n[0] + n[1]*n[1] + n[2]*n[2])    
+    n = n / math.sqrt(n[0]*n[0] + n[1]*n[1] + n[2]*n[2])
     return (n, True)
 
 
@@ -86,7 +88,7 @@ def triangulate_face_shewchuk(face, vnp):
         for ring in face:
             sf = np.hstack( (sf, np.array(ring)) )
         sfv = vnp[sf]
-    
+
         rings = np.zeros(len(face), dtype=np.int64)
         total = 0
         for i in range(len(face)):
@@ -133,14 +135,14 @@ def triangulate_face_shewchuk(face, vnp):
             A = dict(vertices=sfv2d, segments=sg, holes=holes)
         else:
             A = dict(vertices=sfv2d, segments=sg)
-        
+
         try:
             re = triangle.triangulate(A, 'p')
         except:
             print("Houston we have a problem...")
             # re = {}
             return(np.array(face), False)
-        #-- check the output        
+        #-- check the output
         if 'triangles' not in re:
             return([], False)
         re = re['triangles']
@@ -187,9 +189,9 @@ def triangulate_face_mapbox_earcut(face, vnp):
         # print (result.reshape(-1, 3))
 
         for i,each in enumerate(result):
-            # print (sf[i])        
+            # print (sf[i])
             result[i] = sf[each]
-        
+
         # print (result.reshape(-1, 3))
         return (result.reshape(-1, 3), True)
 

tests/test_geom_help.py

@@ -0,0 +1,57 @@
+import typing as t
+
+import numpy as np
+import numpy.typing as npt
+import pytest
+
+from cjio.geom_help import get_normal_newell
+
+
+@pytest.mark.parametrize(
+    ["poly", "expected_normal"],
+    [
+        (
+            [
+                [2195013, 353200, 12283],
+                [2195013, 353200, 8680],
+                [2182302, 347931, 8680],
+                [2182302, 347931, 12159],
+                [2182302, 347931, 12178],
+            ],
+            np.array([-0.38292729, 0.92377848, 0.0]),
+        ),
+        (
+            [
+                [2203406, 332904, 12622],
+                [2203406, 332904, 8680],
+                [2204954, 333543, 8680],
+                [2204954, 333543, 12223],
+                [2204954, 333543, 12584],
+            ],
+            np.array([0.38156054, -0.92434385, 0.0]),
+        ),
+    ],
+)
+def test_get_normal_valid_poly(poly: t.List[t.List[int]], expected_normal: npt.NDArray[t.Any]) -> None:
+    normal, success = get_normal_newell(poly=poly)
+    assert success
+    np.testing.assert_almost_equal(actual=normal, desired=expected_normal)
+
+
+@pytest.mark.parametrize(
+    ["poly", "expected_normal"],
+    [
+        (
+            [[1041, 1009, 1025, 1054, 1087]],
+            np.array([0.0, 0.0, 0.0]),
+        ),
+        (
+            [[[1099, 1098]]],
+            np.array([0.0, 0.0, 0.0]),
+        ),
+    ],
+)
+def test_get_normal_invalid_poly(poly: t.List[t.List[int]], expected_normal: npt.NDArray[t.Any]) -> None:
+    normal, success = get_normal_newell(poly=poly)
+    assert not success
+    np.testing.assert_almost_equal(actual=normal, desired=expected_normal)