Merge pull request #1083 from CadQuery/step

Added quality controls to STEP export for shape and assembly

Author: jmwright

cadquery/assembly.py

@@ -440,14 +440,17 @@ def save(
         exportType: Optional[ExportLiterals] = None,
         tolerance: float = 0.1,
         angularTolerance: float = 0.1,
+        **kwargs,
     ) -> "Assembly":
         """
-        save as STEP or OCCT native XML file
+        Save assembly to a file.
 
-        :param path: filepath
+        :param path: Path and filename for writing.
         :param exportType: export format (default: None, results in format being inferred form the path)
         :param tolerance: the deflection tolerance, in model units. Only used for GLTF, VRML. Default 0.1.
         :param angularTolerance: the angular tolerance, in radians. Only used for GLTF, VRML. Default 0.1.
+        :param **kwargs: Additional keyword arguments.  Only used for STEP.
+            See :meth:`~cadquery.occ_impl.exporters.assembly.exportAssembly`.
         """
 
         if exportType is None:
@@ -458,7 +461,7 @@ def save(
                 raise ValueError("Unknown extension, specify export type explicitly")
 
         if exportType == "STEP":
-            exportAssembly(self, path)
+            exportAssembly(self, path, **kwargs)
         elif exportType == "XML":
             exportCAF(self, path)
         elif exportType == "VRML":

cadquery/occ_impl/exporters/__init__.py

@@ -100,7 +100,10 @@ def export(
             raise ValueError("Only Workplanes can be exported as DXF")
 
     elif exportType == ExportTypes.STEP:
-        shape.exportStep(fname)
+        if opt:
+            shape.exportStep(fname, **opt)
+        else:
+            shape.exportStep(fname)
 
     elif exportType == ExportTypes.STL:
         shape.exportStl(fname, tolerance, angularTolerance)

cadquery/occ_impl/exporters/assembly.py

@@ -21,22 +21,43 @@
 from OCP.RWGltf import RWGltf_CafWriter
 from OCP.TColStd import TColStd_IndexedDataMapOfStringString
 from OCP.Message import Message_ProgressRange
+from OCP.Interface import Interface_Static
 
 from ..assembly import AssemblyProtocol, toCAF, toVTK
 
 
-def exportAssembly(assy: AssemblyProtocol, path: str) -> bool:
+def exportAssembly(assy: AssemblyProtocol, path: str, **kwargs) -> bool:
     """
-    Export an assembly to a step a file.
+    Export an assembly to a STEP file.
+
+    kwargs is used to provide optional keyword arguments to configure the exporter.
+
+    :param assy: assembly
+    :param path: Path and filename for writing
+    :param write_pcurves: Enable or disable writing parametric curves to the STEP file. Default True.
+
+        If False, writes STEP file without pcurves. This decreases the size of the resulting STEP file.
+    :type write_pcurves: boolean
+    :param precision_mode: Controls the uncertainty value for STEP entities. Specify -1, 0, or 1. Default 0.
+        See OCCT documentation.
+    :type precision_mode: int
     """
 
+    # Handle the extra settings for the STEP export
+    pcurves = 1
+    if "write_pcurves" in kwargs and not kwargs["write_pcurves"]:
+        pcurves = 0
+    precision_mode = kwargs["precision_mode"] if "precision_mode" in kwargs else 0
+
     _, doc = toCAF(assy, True)
 
     session = XSControl_WorkSession()
     writer = STEPCAFControl_Writer(session, False)
     writer.SetColorMode(True)
     writer.SetLayerMode(True)
     writer.SetNameMode(True)
+    Interface_Static.SetIVal_s("write.surfacecurve.mode", pcurves)
+    Interface_Static.SetIVal_s("write.precision.mode", precision_mode)
     writer.Transfer(doc, STEPControl_StepModelType.STEPControl_AsIs)
 
     status = writer.Write(path)

cadquery/occ_impl/shapes.py

@@ -230,6 +230,8 @@
 # for catching exceptions
 from OCP.Standard import Standard_NoSuchObject, Standard_Failure
 
+from OCP.Interface import Interface_Static
+
 from math import pi, sqrt
 import warnings
 
@@ -449,12 +451,31 @@ def exportStl(
 
         return writer.Write(self.wrapped, fileName)
 
-    def exportStep(self, fileName: str) -> IFSelect_ReturnStatus:
+    def exportStep(self, fileName: str, **kwargs) -> IFSelect_ReturnStatus:
         """
-        Export this shape to a STEP file
+        Export this shape to a STEP file.
+
+        kwargs is used to provide optional keyword arguments to configure the exporter.
+
+        :param fileName: Path and filename for writing.
+        :param write_pcurves: Enable or disable writing parametric curves to the STEP file. Default True.
+
+            If False, writes STEP file without pcurves. This decreases the size of the resulting STEP file.
+        :type write_pcurves: boolean
+        :param precision_mode: Controls the uncertainty value for STEP entities. Specify -1, 0, or 1. Default 0.
+            See OCCT documentation.
+        :type precision_mode: int
         """
 
+        # Handle the extra settings for the STEP export
+        pcurves = 1
+        if "write_pcurves" in kwargs and not kwargs["write_pcurves"]:
+            pcurves = 0
+        precision_mode = kwargs["precision_mode"] if "precision_mode" in kwargs else 0
+
         writer = STEPControl_Writer()
+        Interface_Static.SetIVal_s("write.surfacecurve.mode", pcurves)
+        Interface_Static.SetIVal_s("write.precision.mode", precision_mode)
         writer.Transfer(self.wrapped, STEPControl_AsIs)
 
         return writer.Write(fileName)

doc/classreference.rst

@@ -95,3 +95,7 @@ Class Details
 .. automodule:: cadquery.selectors
    :show-inheritance: 
    :members:
+
+.. automodule:: cadquery.occ_impl.exporters.assembly
+   :show-inheritance:
+   :members:

tests/test_assembly.py

@@ -179,17 +179,29 @@ def test_assembly(simple_assy, nested_assy):
     assert kvs[-1][0] == "TOP"
 
 
-def test_step_export(nested_assy):
-
-    exportAssembly(nested_assy, "nested.step")
+def test_step_export(nested_assy, tmp_path_factory):
+    # Use a temporary directory
+    tmpdir = tmp_path_factory.mktemp("out")
+    nested_path = os.path.join(tmpdir, "nested.step")
+    nested_options_path = os.path.join(tmpdir, "nested_options.step")
+
+    exportAssembly(nested_assy, nested_path)
+    exportAssembly(
+        nested_assy, nested_options_path, write_pcurves=False, precision_mode=0
+    )
 
-    w = cq.importers.importStep("nested.step")
+    w = cq.importers.importStep(nested_path)
+    o = cq.importers.importStep(nested_options_path)
     assert w.solids().size() == 4
+    assert o.solids().size() == 4
 
     # check that locations were applied correctly
     c = cq.Compound.makeCompound(w.solids().vals()).Center()
     c.toTuple()
     assert pytest.approx(c.toTuple()) == (0, 4, 0)
+    c2 = cq.Compound.makeCompound(o.solids().vals()).Center()
+    c2.toTuple()
+    assert pytest.approx(c2.toTuple()) == (0, 4, 0)
 
 
 def test_native_export(simple_assy):

tests/test_exporters.py

@@ -2,7 +2,7 @@
     Tests basic workplane functionality
 """
 # core modules
-import sys
+import os
 import io
 from pathlib import Path
 import re
@@ -15,6 +15,27 @@
 from OCP.BRepBuilderAPI import BRepBuilderAPI_MakeEdge
 
 
+def test_step_options(tmp_path_factory):
+    """
+    Exports a box using the options to decrease STEP file size and
+    then imports that STEP to validate it.
+    """
+    # Use a temporary directory
+    tmpdir = tmp_path_factory.mktemp("out")
+    box_path = os.path.join(tmpdir, "out.step")
+
+    # Simple object to export
+    box = Workplane().box(1, 1, 1)
+
+    # Export the STEP with the size-saving options and then import it back in
+    box.val().exportStep(box_path, write_pcurves=False, precision_mode=0)
+    w = importers.importStep(box_path)
+
+    # Make sure there was a valid box in the exported file
+    assert w.solids().size() == 1
+    assert w.faces().size() == 6
+
+
 class TestExporters(BaseTest):
     def _exportBox(self, eType, stringsToFind, tolerance=0.1, angularTolerance=0.1):
         """