Add align_z argument to pack() Method.

docs/tips.rst

@@ -172,6 +172,14 @@ padding (right):
  :align: right
 
 
+By default, the original Z value of all objects packed using the :meth:`pack.pack` function is preserved. 
+If you want to align all objects so that they are "placed" on the zero Z coordinate, the :meth:`pack` 
+function has an `align_z` argument. When set to `True`, this will align all objects. 
+
+This can be useful, for example, when preparing print setups for 3D printing, giving you full control 
+over this alignment so you don't have to leave it to the slicer.
+
+
 .. _are_glob_imports_bad_practice:
 
 ***********************************************

src/build123d/pack.py

@@ -14,7 +14,7 @@
 from dataclasses import dataclass
 from typing import Callable, Collection, Optional, cast
 
-from build123d import Location, Shape
+from build123d import Location, Shape, Pos
 
 
 def _pack2d(
@@ -119,16 +119,26 @@ def grow_down(w, h):
  return [(t[1], t[2]) for t in sorted(translations, key=lambda t: t[0])]
 
 
-def pack(objects: Collection[Shape], padding: float) -> Collection[Shape]:
- """Pack objects in a squarish area in Plane.XY."""
+def pack(objects: Collection[Shape], padding: float, align_z: bool = False) -> Collection[Shape]:
+ """Pack objects in a squarish area in Plane.XY.
+
+ Args:
+ objects (Collection[Shape]): objects to arrange
+ padding (float): space between objects
+ align_z (bool, optional): align shape bottoms to Plane.XY. Defaults to False.
+
+ Returns:
+ Collection[Shape]: rearranged objects
+ """
+
  bounding_boxes = {o: o.bounding_box().size + (padding, padding) for o in objects}
  translations = _pack2d(
  objects,
  width_fn=lambda o: bounding_boxes[cast(Shape, o)].X,
  length_fn=lambda o: bounding_boxes[cast(Shape, o)].Y,
  )
  translated = [
- Location((t[0] - o.bounding_box().min.X, t[1] - o.bounding_box().min.Y, 0)) * o
+ Location((t[0] - o.bounding_box().min.X, t[1] - o.bounding_box().min.Y, 0)) * Pos((0, 0, -o.bounding_box().min.Z if align_z else 0)) * o
  for (o, t) in zip(objects, translations)
  ]