Merge pull request #941 from juney-lee/main

bug in compas.geometry.normal_polygon

Author: tomvanmele

CHANGELOG.md

@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+* Fixed bug in `normal_polygon` in `compas.geometry`.
 * Fixed bug in Blender mesh conversion.
 * Changed Rhino plugin installer to check for and install required plugin packages.
 * Refactor robot model artists to use the same `Mesh.to_vertices_and_faces` everywhere.

src/compas/geometry/_core/normals.py

@@ -63,9 +63,9 @@ def normal_polygon(polygon, unitized=True):
         n = cross_vectors(oa, ob)
         oa = ob
 
-        nx += n[0]
-        ny += n[1]
-        nz += n[2]
+        nx += n[0] * 0.5
+        ny += n[1] * 0.5
+        nz += n[2] * 0.5
 
     if not unitized:
         return [nx, ny, nz]

tests/compas/geometry/test_core.py

@@ -19,6 +19,7 @@
 from compas.geometry import area_polygon_xy
 from compas.geometry import area_triangle
 from compas.geometry import area_triangle_xy
+from compas.geometry import normal_polygon
 
 
 @pytest.fixture
@@ -202,3 +203,15 @@ def test_area_triangle(triangle, R):
     assert close(area_triangle(triangle.points), 0.5)
     assert close(area_triangle_xy(triangle.points), 0.0)
     assert close(triangle.area, 0.5)
+
+
+# ==============================================================================
+# normals
+# ==============================================================================\
+
+def test_normal_polygon():
+    polygon = [(0, 0, 0), (10, 0, 0), (10, 10, 0), (0, 10, 0)]
+    normal = normal_polygon(polygon, unitized=False)
+    area = area_polygon(polygon)
+    assert close(area, 100.0)
+    assert close(area, length_vector(normal))