fix bug in normals calc

Author: tomvanmele

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fixed box scaling.
 * Fixed a bug in `Polyline.divide_polyline_by_length` related to a floating point rounding error.
 * Fixed bug in `RobotModel.zero_configuration`.
+* Fixed bug in `compas.geometry.normals`.
 
 ### Removed
 

src/compas/geometry/_core/normals.py

@@ -67,7 +67,7 @@ def normal_polygon(polygon, unitized=True):
         nz += n[2]
 
     if not unitized:
-        return nx, ny, nz
+        return [0.5 * nx, 0.5 * ny, 0.5 * nz]
 
     return normalize_vector([nx, ny, nz])
 
@@ -97,9 +97,9 @@ def normal_triangle(triangle, unitized=True):
     ac = subtract_vectors(c, a)
     n = cross_vectors(ab, ac)
     if not unitized:
-        return n
-    lvec = length_vector(n)
-    return n[0] / lvec, n[1] / lvec, n[2] / lvec
+        return [0.5 * n[0], 0.5 * n[1], 0.5 * n[2]]
+    lvec = 1 / length_vector(n)
+    return [lvec * n[0], lvec * n[1], lvec * n[2]]
 
 
 def normal_triangle_xy(triangle, unitized=True):
@@ -127,15 +127,6 @@ def normal_triangle_xy(triangle, unitized=True):
     ac = subtract_vectors_xy(c, a)
     n = cross_vectors_xy(ab, ac)
     if not unitized:
-        return n
-    lvec = length_vector_xy(n)
-    return n[0] / lvec, n[1] / lvec, n[2] / lvec
-
-
-# ==============================================================================
-# Main
-# ==============================================================================
-
-if __name__ == "__main__":
-
-    pass
+        return [0.5 * n[0], 0.5 * n[1], 0]
+    lvec = 1 / length_vector_xy(n)
+    return [lvec * n[0], lvec * n[1], 0]

tests/compas/datastructures/test_mesh.py

@@ -9,6 +9,7 @@
 from compas.geometry import Box
 from compas.geometry import Polygon
 from compas.geometry import Translation
+from compas.geometry import allclose
 
 
 @pytest.fixture
@@ -585,7 +586,7 @@ def test_face_coordinates():
 
 def test_face_normal():
     mesh = Mesh.from_obj(compas.get('quadmesh.obj'))
-    assert mesh.face_normal(0) == [0.5435358481001584, -0.16248515023849733, 0.8235091728584537]
+    assert allclose(mesh.face_normal(0), [0.5435358481001584, -0.16248515023849733, 0.8235091728584537], tol=1e-6)
 
 
 def test_face_centroid():

tests/compas/geometry/test_polygon.py

@@ -52,4 +52,4 @@ def test___setitem__():
     polygon[4] = point
     assert polygon[4] == point
     assert isinstance(polygon[4], Point)
-    assert polygon.lines[-2].end == point
+    assert polygon.lines[-2].end == point