fix(examples): free hay-bale's bmesh on every path; per-run depsgraph-export OBJ

hay-bale (#401): a measurement helper built a bmesh inside
`try: ... finally: pass`, so its early `return []` leaked the BMesh and
the later bm.free() was unprotected; the --stray-vert falsifier path did
from_mesh/to_mesh/free with no try at all, the literal "WRONG" example
of the always-free-bmesh rule. Both now free in finally. BVHTree.FromBMesh
copies the geometry, so freeing before the ray casts is safe: the
piece's full output is byte-identical before and after.

depsgraph-export (#404): the export wrote gettempdir()/depsgraph_export.obj
and never removed it, so a previous run's OBJ could satisfy the "file
exists" check when an export wrote nothing (and Blender points TMPDIR at
the working directory). It now uses a pid-suffixed name and deletes the
.obj and .mtl before and after.

Closes #404
Refs #401

Signed-off-by: TMHSDigital <154358121+TMHSDigital@users.noreply.github.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: TMHSDigital

examples/depsgraph-export/depsgraph_export.py

@@ -369,22 +369,36 @@ def check(shell, obj_path, unevaluated=False):
     V, E, F, S = len(me.vertices), len(me.edges), len(me.polygons), len(me.loops)
     expected = catmull_clark_vcount(V, E, F, S, SUBSURF_LEVELS)
 
-    out = obj_path or os.path.join(tempfile.gettempdir(), "depsgraph_export.obj")
+    # A per-run name, removed before and after: a fixed name let a previous
+    # run's OBJ satisfy the "file exists" check below when this export wrote
+    # nothing, and Blender points TMPDIR at the working directory (#404).
+    out = obj_path or os.path.join(tempfile.gettempdir(),
+                                   f"depsgraph_export_{os.getpid()}.obj")
     os.makedirs(os.path.dirname(os.path.abspath(out)) or ".", exist_ok=True)
-    # obj_export writes the evaluated (modifier-applied) geometry by default
-    bpy.ops.wm.obj_export(
-        filepath=out,
-        export_selected_objects=False,
-        apply_modifiers=not unevaluated,
-    )
-    if not (os.path.exists(out) and os.path.getsize(out) > 0):
-        print("ERROR: no OBJ written", file=sys.stderr)
-        return 4
-    exported = 0
-    with open(out, encoding="utf-8") as f:
-        for line in f:
-            if line.startswith("v "):
-                exported += 1
+    sidecars = [out, os.path.splitext(out)[0] + ".mtl"]
+    for path in sidecars:
+        if os.path.exists(path):
+            os.remove(path)
+    try:
+        # obj_export writes the evaluated (modifier-applied) geometry by default
+        bpy.ops.wm.obj_export(
+            filepath=out,
+            export_selected_objects=False,
+            apply_modifiers=not unevaluated,
+        )
+        if not (os.path.exists(out) and os.path.getsize(out) > 0):
+            print("ERROR: no OBJ written", file=sys.stderr)
+            return 4
+        exported = 0
+        with open(out, encoding="utf-8") as f:
+            for line in f:
+                if line.startswith("v "):
+                    exported += 1
+    finally:
+        if not obj_path:
+            for path in sidecars:
+                if os.path.exists(path):
+                    os.remove(path)
 
     print(f"shell_cage V={V} E={E} F={F} S={S} levels={SUBSURF_LEVELS} "
           f"shell_eval_vcount={shell_eval} closed_form={expected}")

showcase/hay-bale/hay_bale.py

@@ -453,9 +453,11 @@ def belt_seat_depths(me, loaf_comp, belt_comp, station_x, segs):
                     pass
         if not bm.faces:
             return []
+        # FromBMesh copies the geometry into the tree, so the BMesh can be
+        # freed here, on the early return and the normal path alike.
         bvh = BVHTree.FromBMesh(bm)
     finally:
-        pass
+        bm.free()
     zs = [me.vertices[i].co.z for i in loaf_comp]
     cz = 0.5 * (min(zs) + max(zs))
     buckets = {}
@@ -498,7 +500,6 @@ def depth(co):
         vals = [d for d in (depth(co) for co in buckets[k]) if d is not None]
         if vals:
             depths.append(max(vals))
-    bm.free()
     return depths
 
 
@@ -1142,13 +1143,15 @@ def check(skip_decimate, lift_z=False, stray_vert=False, slack_belt=False,
         low.data.update()
     if stray_vert:
         bm = bmesh.new()
-        bm.from_mesh(low.data)
-        # Inside the existing AABB: a stray vertex parked above the bale
-        # blew the bounding-box budget (exit 8) before the hygiene gate
-        # could see it, so it proved nothing about hygiene.
-        bm.verts.new((0.0, 0.0, BALE_Z * 0.5))
-        bm.to_mesh(low.data)
-        bm.free()
+        try:
+            bm.from_mesh(low.data)
+            # Inside the existing AABB: a stray vertex parked above the bale
+            # blew the bounding-box budget (exit 8) before the hygiene gate
+            # could see it, so it proved nothing about hygiene.
+            bm.verts.new((0.0, 0.0, BALE_Z * 0.5))
+            bm.to_mesh(low.data)
+        finally:
+            bm.free()
         low.data.update()
 
     if low.data is None or len(low.data.polygons) < 6: