Merge pull request #872 from CadQuery/ezdxf-spline-fix

DXF spline export fix

Author: jmwright

cadquery/occ_impl/exporters/dxf.py

@@ -76,16 +76,23 @@ def _dxf_spline(e: Edge, msp: ezdxf.layouts.Modelspace, plane: Plane):
         curve, adaptor.FirstParameter(), adaptor.LastParameter(), CURVE_TOLERANCE
     )
 
+    # need to apply the transform on the geometry level
+    spline.Transform(plane.fG.wrapped.Trsf())
+
     order = spline.Degree() + 1
     knots = list(spline.KnotSequence())
     poles = [(p.X(), p.Y(), p.Z()) for p in spline.Poles()]
+    weights = (
+        [spline.Weight(i) for i in range(1, spline.NbPoles() + 1)]
+        if spline.IsRational()
+        else None
+    )
 
-    weights = list(spline.Weights()) if spline.IsRational() else None
+    if spline.IsPeriodic():
+        pad = spline.NbKnots() - spline.LastUKnotIndex()
+        poles += poles[:pad]
 
-    if spline.IsClosed():
-        dxf_spline = ezdxf.math.BSplineClosed(poles, order, knots, weights)
-    else:
-        dxf_spline = ezdxf.math.BSpline(poles, order, knots, weights)
+    dxf_spline = ezdxf.math.BSpline(poles, order, knots, weights)
 
     msp.add_spline().apply_construction_tool(dxf_spline)
 

tests/test_exporters.py

@@ -9,6 +9,8 @@
 from cadquery import *
 from cadquery import exporters, importers
 from tests import BaseTest
+from OCP.GeomConvert import GeomConvert
+from OCP.BRepBuilderAPI import BRepBuilderAPI_MakeEdge
 
 
 class TestExporters(BaseTest):
@@ -168,6 +170,43 @@ def testDXF(self):
         self.assertAlmostEqual(s4.val().Area(), s4_i.val().Area(), 6)
         self.assertAlmostEqual(s4.edges().size(), s4_i.edges().size())
 
+        # test periodic spline
+        w = Workplane().spline([(1, 1), (2, 2), (3, 2), (3, 1)], periodic=True)
+        exporters.dxf.exportDXF(w, "res5.dxf")
+
+        w_i = importers.importDXF("res5.dxf")
+
+        self.assertAlmostEqual(w.val().Length(), w_i.wires().val().Length(), 6)
+
+        # test rational spline
+        c = Edge.makeCircle(1)
+        adaptor = c._geomAdaptor()
+        curve = GeomConvert.CurveToBSplineCurve_s(adaptor.Curve().Curve())
+
+        e = Workplane().add(Edge(BRepBuilderAPI_MakeEdge(curve).Shape()))
+        exporters.dxf.exportDXF(e, "res6.dxf")
+
+        e_i = importers.importDXF("res6.dxf")
+
+        self.assertAlmostEqual(e.val().Length(), e_i.wires().val().Length(), 6)
+
+        # test non-planar section
+        s5 = (
+            Workplane()
+            .spline([(0, 0), (1, 0), (1, 1), (0, 1)])
+            .close()
+            .extrude(1, both=True)
+            .translate((-3, -4, 0))
+        )
+
+        s5.plane = Plane(origin=(0, 0.1, 0.5), normal=(0.05, 0.05, 1))
+        s5 = s5.section()
+        exporters.dxf.exportDXF(s5, "res7.dxf")
+
+        s5_i = importers.importDXF("res7.dxf")
+
+        self.assertAlmostEqual(s5.val().Area(), s5_i.val().Area(), 4)
+
     def testTypeHandling(self):
 
         with self.assertRaises(ValueError):