fusion: the print frame no longer turns the part 90 degrees -- an XY bed hands the engine the part as the site sees it (v0.6.2)

PrintFrame.from_bed took x = n x ref, so a bed on the XY plane gave print x = world
+Y, y = world -X. The engine isn't the same under a turn about z: the headset got 95
walls / 144 tines in Fusion, 93 / 140 on the site and CLI. x is now ref projected onto
the bed, so an XY bed is the identity frame. Chairs, lampshade, bunny, gree, bear,
zombie, lighthouse and the headset now match the CLI.

plugins/fusion/SupportFins/SupportFins.manifest

@@ -6,7 +6,7 @@
 	"description": {
 		"": "printfins.com supports that live in the model. Insert Support Fins: the website's breakaway fins and bed pad under a part's overhangs, from the website's own engine."
 	},
-	"version": "0.6.1",
+	"version": "0.6.2",
 	"runOnStartup": false,
 	"supportedOS": "windows|mac",
 	"editEnabled": true

plugins/fusion/SupportFins/fusion_bridge.py

@@ -128,8 +128,13 @@ class PrintFrame:
 
         axes = [adsk.core.Vector3D.create(1, 0, 0), adsk.core.Vector3D.create(0, 1, 0),
                 adsk.core.Vector3D.create(0, 0, 1)]
+        # Print x is the world axis lying flattest on the bed, projected onto it, so
+        # a bed on the XY plane gives print axes = world axes: the part goes to the
+        # engine the way the site sees the same STL. (x = n x ref turned every part
+        # 90 degrees, and the engine's placement isn't the same under a turn.)
         ref = min(axes, key=lambda a: abs(a.dotProduct(n)))
-        x = n.crossProduct(ref)
+        k = ref.dotProduct(n)
+        x = adsk.core.Vector3D.create(ref.x - k * n.x, ref.y - k * n.y, ref.z - k * n.z)
         x.normalize()
         y = n.crossProduct(x)
         y.normalize()

plugins/fusion/tests/test_fins.py

@@ -526,6 +526,25 @@ class FusionSide(unittest.TestCase):
         self.assertAlmostEqual(min(allc[1::3]), 0.3, places=4)          # cm, along Y
         self.assertLessEqual(max(allc[1::3]), max(c / 10.0 for c in yup[1::3]) + 1e-4)
 
+    def test_an_xy_bed_hands_the_engine_the_part_unturned(self):
+        # The site fins the STL as it sits; Fusion must give the engine the same
+        # soup, or placement differs (the headset got 95 walls here, 93 on the site).
+        part = posed(read_stl('lbracket'), 35)
+        design, body = mesh_design(part)
+        frame = fb.PrintFrame.from_bed(design.rootComponent.xYConstructionPlane, body, APP)
+        soup = fb.body_soup(body, frame)
+        self.assertEqual(len(soup), len(part))
+        self.assertLess(max(abs(a - b) for a, b in zip(soup, part)), 1e-4)
+
+    def test_the_print_frame_is_right_handed_on_any_bed(self):
+        design, body = mesh_design(posed(read_stl('lbracket'), 35))
+        for n in ((0, 0, 1), (0, 1, 0), (1, 0, 0), (0.3, -0.5, 0.81)):
+            frame = fb.PrintFrame.from_bed(fake_adsk.ConstructionPlane((0, 0, 0), n), body, APP)
+            x, y, z = (fake_adsk.Vec(*v) for v in (frame.x, frame.y, frame.z))
+            c = x.crossProduct(y)
+            self.assertAlmostEqual(c.dotProduct(z), 1.0, places=9)
+            self.assertAlmostEqual(x.dotProduct(y), 0.0, places=9)
+
     def test_part_through_the_bed_is_refused_and_floating_is_flagged(self):
         part = posed(read_stl('lbracket'), 35, (0, 0, -5))
         design, _ = mesh_design(part)