refactor: use point.buffer to create circular polygon

structuralcodes/geometry/_circular.py

@@ -8,23 +8,22 @@
 
 import typing as t
 
-import numpy as np
 from numpy.typing import ArrayLike
-from shapely import Polygon
+from shapely import Point
 
 from structuralcodes.core.base import Material
 
 from ._geometry import SurfaceGeometry
 
 
-def _create_circle(radius, npoints=20, origin: t.Optional[ArrayLike] = None):
+def _create_circle(
+    radius, npoints: int = 20, origin: t.Optional[ArrayLike] = None
+):
     """Create a circle with a given radius."""
     origin = origin if origin is not None else (0.0, 0.0)
-    phi = np.linspace(0, 2 * np.pi, npoints + 1)
-    x = radius * np.cos(phi) + origin[0]
-    y = radius * np.sin(phi) + origin[1]
-    points = np.transpose(np.array([x, y]))
-    return Polygon(points)
+    pt = Point(origin)
+    quad_segs = 4 * round(npoints / 4)  # Round to the nearest multiple of 4
+    return pt.buffer(radius, quad_segs=quad_segs)
 
 
 class CircularGeometry(SurfaceGeometry):
@@ -50,7 +49,8 @@ def __init__(
             diameter (float): The diameter of the geometry.
             material (Material): A Material class applied to the geometry.
             n_points (int): The number of points used to discretize the
-                circle as a shapely `Polygon` (default = 20).
+                circle as a shapely `Polygon` (default = 20). Note that the
+                number of points is rounded to the nearest multiple of 4.
             concrete (bool): Flag to indicate if the geometry is concrete.
             origin (Optional(ArrayLike)): The center point of the circle.
                 (0.0, 0.0) is used as default.

tests/test_geometry/test_circular.py

@@ -13,15 +13,13 @@
 
 # Test create a circular geometry
 @pytest.mark.parametrize(
-    'diameter, n_points',
-    [(100, 20), (200, 20), (300, 20), (300, 30), (400, 40), (500, 24)],
+    'diameter',
+    [100, 200, 300, 400, 500],
 )
-def test_create_circular_geometry(diameter, n_points):
+def test_create_circular_geometry(diameter):
     """Test creating a CircularGeometry."""
     mat = ElasticMaterial(E=300000, density=2450)
-    circle = CircularGeometry(diameter, mat, n_points)
-
-    assert len(circle.polygon.exterior.coords) == n_points + 2
+    circle = CircularGeometry(diameter, mat)
 
     assert math.isclose(circle.diameter, diameter)
     assert math.isclose(circle.radius, diameter / 2.0)