fixed unexpected behavior for opposite parallel planes.

CHANGELOG.md

@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
+* Fixed unexpected behavior for method `Plane.is_parallel` for opposite normals.
 
 ### Added
 

src/compas/geometry/plane.py

@@ -384,9 +384,13 @@ def is_parallel(self, other, tol=None):
         >>> plane2 = Plane([1.0, 1.0, 1.0], [0.0, 0.0, 1.0])
         >>> plane1.is_parallel(plane2)
         True
+        >>> plane1 = Plane.worldXY()
+        >>> plane2 = Plane([1.0, 1.0, 1.0], [0.0, 0.0, -1.0])
+        >>> plane1.is_parallel(plane2)
+        True
 
         """
-        return TOL.is_close(self.normal.dot(other.normal), 1, rtol=0, atol=tol)
+        return TOL.is_close(abs(self.normal.dot(other.normal)), 1, rtol=0, atol=tol)
 
     def is_perpendicular(self, other, tol=None):
         """Verify if this plane is perpendicular to another plane.

src/compas_ghpython/components_cpython/Compas_Info/code.py

@@ -3,9 +3,10 @@
 Displays information about the active COMPAS environment.
 """
 
+import os
+
 import Grasshopper
 
-import os
 import compas
 
 

tests/compas/geometry/test_plane.py

@@ -76,3 +76,13 @@ def test_plane_from_three_points():
 
     result = Plane.from_three_points(pt1, pt2, pt3)
     assert result == ([0, 0, 0], [0, 0, 1])
+
+
+def test_plane_is_parallel():
+    plane1 = Plane.worldXY()
+    plane2 = Plane([1.0, 1.0, 1.0], [0.0, 0.0, 1.0])
+    assert plane1.is_parallel(plane2)
+
+    plane1 = Plane.worldXY()
+    plane2 = Plane([1.0, 1.0, 1.0], [0.0, 0.0, -1.0])
+    assert plane1.is_parallel(plane2)