Geometry.align_center() -> Ability to align geometries to a point

sectionproperties/pre/geometry.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 from ntpath import join
-from typing import List, Optional, Union, Tuple, Any
+from typing import List, Optional, Union, Tuple, List, Any
 
 import copy
 import math
@@ -479,31 +479,47 @@ def align_to(
 
         return new_geom
 
-    def align_center(self, align_to: Optional[Geometry] = None):
+    def align_center(
+        self, align_to: Optional[Union[Geometry, Tuple[float, float]]] = None
+    ):
         """
         Returns a new Geometry object, translated in both x and y, so that the
-        center-point of the new object's centroid will be aligned with
-        centroid of the object in 'align_to'. If 'align_to' is None then the new
-        object will be aligned with it's centroid at the origin.
+        the new object's centroid will be aligned with the centroid of the object
+        in 'align_to'. If 'align_to' is an x, y coordinate, then the centroid will
+        be aligned to the coordinate. If 'align_to' is None then the new
+        object will be aligned with its centroid at the origin.
 
         :param align_to: Another Geometry to align to or None (default is None)
-        :type align_to: Optional[:class:`~sectionproperties.pre.geometry.Geometry`]
+        :type align_to: Optional[Union[:class:`~sectionproperties.pre.geometry.Geometry`, Tuple[float, float]]]
 
         :return: Geometry object translated to new alignment
         :rtype: :class:`~sectionproperties.pre.geometry.Geometry`
         """
         cx, cy = list(self.geom.centroid.coords)[0]
-        # Suggested by Agent 6-6-6: Hard-rounding of cx and cy allows
+        # Suggested by @Agent6-6-6: Hard-rounding of cx and cy allows
         # for greater precision in placing geometry with its centroid
         # near [0, 0]. True [0, 0] placement will not be possible due
         # to floating point errors.
         if align_to is None:
             shift_x, shift_y = round(-cx, self.tol), round(-cy, self.tol)
 
-        else:
+        elif isinstance(align_to, Geometry):
             align_cx, align_cy = list(align_to.geom.centroid.coords)[0]
             shift_x = round(align_cx - cx, self.tol)
             shift_y = round(align_cy - cy, self.tol)
+
+        else:
+            try:
+                point_x, point_y = align_to
+                shift_x = round(point_x - cx, self.tol)
+                shift_y = round(point_y - cy, self.tol)
+            except (
+                TypeError,
+                ValueError,
+            ):  # align_to not subscriptable, incorrect length, etc.
+                raise ValueError(
+                    f"align_to must be either a Geometry object or an x, y coordinate, not {align_to}."
+                )
         new_geom = self.shift_section(x_offset=shift_x, y_offset=shift_y)
         return new_geom
 
@@ -1555,20 +1571,23 @@ def mirror_section(
         new_geom = CompoundGeometry(geoms_acc)
         return new_geom
 
-    def align_center(self, align_to: Optional[Geometry] = None):
+    def align_center(
+        self, align_to: Optional[Union[Geometry, Tuple[float, float]]] = None
+    ):
         """
         Returns a new CompoundGeometry object, translated in both x and y, so that the
         center-point of the new object's material-weighted centroid will be aligned with
-        centroid of the object in 'align_to'. If 'align_to' is None then the new
-        object will be aligned with it's centroid at the origin.
+        centroid of the object in 'align_to'. If 'align_to' is an x, y coordinate, then
+        the centroid will be aligned to the coordinate. If 'align_to' is None then the new
+        object will be aligned with its centroid at the origin.
 
         Note: The material-weighted centroid refers to when individual geometries within
         the CompoundGeometry object have been assigned differing materials. The centroid
         of the compound geometry is calculated by using the E modulus of each
         geometry's assigned material.
 
-        :param align_to: Another Geometry to align to or None (default is None)
-        :type align_to: Optional[:class:`~sectionproperties.pre.geometry.Geometry`]
+        :param align_to: Another Geometry to align to, an xy coordinate, or None (default is None)
+        :type align_to: Optional[Union[:class:`~sectionproperties.pre.geometry.Geometry`, Tuple[float, float]]]
 
         :return: Geometry object translated to new alignment
         :rtype: :class:`~sectionproperties.pre.geometry.Geometry`
@@ -1597,10 +1616,21 @@ def align_center(self, align_to: Optional[Geometry] = None):
                 round(-weighted_cy, self.tol),
             )
 
-        else:
+        elif isinstance(Geometry):
             align_cx, align_cy = list(align_to.geom.centroid.coords)[0]
             shift_x = round(align_cx - weighted_cx, self.tol)
             shift_y = round(align_cy - weighted_cy, self.tol)
+
+        else:
+            try:
+                point_x, point_y = align_to
+                shift_x = round(point_x - weighted_cx, self.tol)
+                shift_y = round(point_y - weighted_cy, self.tol)
+            except (TypeError, ValueError):
+                raise ValueError(
+                    f"align_to must be either a Geometry object or an x, y coordinate, not {align_to}."
+                )
+
         new_geom = self.shift_section(x_offset=shift_x, y_offset=shift_y)
         return new_geom
 

sectionproperties/tests/test_sections.py

@@ -532,3 +532,24 @@ def test_warping_disjoint_warning():
     sec.calculate_geometric_properties()
     with pytest.warns(UserWarning):
         sec.calculate_warping_properties()
+
+
+def test_align_center():
+    rect = rectangular_section(d=200, b=70)
+    circ = circular_section(d=200, n=30)
+    rect = rect.rotate_section(-45, rot_point=[0, 0])
+    rect_point = rect.points[1]
+    circ = circ.align_center(rect_point)
+    circ_x, circ_y = circ.calculate_centroid()
+    assert pytest.approx(circ_x) == 49.497474683057995
+    assert pytest.approx(circ_y) == -49.49747468305799
+
+    circ = circ.align_center()
+    circ_x, circ_y = circ.calculate_centroid()
+    assert pytest.approx(circ_x) == 0
+    assert pytest.approx(circ_y) == 0
+
+    circ = circ.align_center(rect)
+    circ_x, circ_y = circ.calculate_centroid()
+    assert pytest.approx(circ_x) == 95.45941546018399
+    assert pytest.approx(circ_y) == 45.961940777125974

setup.cfg

@@ -51,4 +51,5 @@ rhino =
 
 test =
   rhino-shapley-interop>=0.0.4
+  pytest
   pytest_check