Add the solidcraft-checking skill (#880)

skills/solidcraft-checking/scripts/compare_step.py

@@ -0,0 +1,54 @@
+"""Compare two STEP files exactly with OCCT: volume, area, centre of mass, and the volume of their
+symmetric difference (xor) with where each piece sits. Exits 1 when xor exceeds the tolerance.
+
+Run: uv run --no-project --with build123d python compare_step.py ACTUAL.step EXPECTED.step
+"""
+
+import argparse
+import sys
+
+from build123d import CenterOf, Shape, import_step
+
+from run import number, point
+
+PIECES_SHOWN = 5
+
+
+def fused(shape: Shape) -> Shape:
+    """Overlapping solids in one file would otherwise count their overlap twice."""
+    solids = shape.solids()
+    return solids[0].fuse(*solids[1:]) if len(solids) > 1 else shape
+
+
+def pieces(shape: Shape) -> list[tuple[float, tuple, tuple]]:
+    found = [(s.volume, tuple(s.bounding_box().min), tuple(s.bounding_box().max)) for s in shape.solids()]
+    return sorted(found, reverse=True)
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
+    parser.add_argument("actual")
+    parser.add_argument("expected")
+    parser.add_argument("--tolerance", type=float, default=1e-3, help="largest xor volume that counts as equal, mm3")
+    args = parser.parse_args()
+
+    actual, expected = fused(import_step(args.actual)), fused(import_step(args.expected))
+    shift = max(abs(a - b) for a, b in zip(actual.center(CenterOf.MASS), expected.center(CenterOf.MASS)))
+    print(f"volume {number(actual.volume)} vs {number(expected.volume)} mm3")
+    print(f"area {number(actual.area)} vs {number(expected.area)} mm2")
+    print(f"centre of mass shift {number(shift)} mm")
+
+    sides = {"only in actual": pieces(actual - expected), "only in expected": pieces(expected - actual)}
+    xor = sum(volume for found in sides.values() for volume, _, _ in found)
+    count = sum(map(len, sides.values()))
+    print(f"xor {number(xor)} mm3" + (f" in {count} pieces" if count else ""))
+    for side, found in sides.items():
+        for volume, low, high in found[:PIECES_SHOWN]:
+            print(f"  {side}: {number(volume)} mm3 at {point(low)}..{point(high)}")
+        if len(found) > PIECES_SHOWN:
+            print(f"  {side}: {len(found) - PIECES_SHOWN} smaller pieces")
+    sys.exit(1 if xor > args.tolerance else 0)
+
+
+if __name__ == "__main__":
+    main()