Add STEP Import for Assemblies #1779

jmwright · 2025-02-26T16:36:44Z

The goal is to make it possible to round-trip assemblies to and from STEP without loss of data. This data can include:

codecov · 2025-02-26T21:50:50Z

Codecov Report

❌ Patch coverage is 95.93496% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.84%. Comparing base (8431073) to head (1543908).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
cadquery/occ_impl/importers/assembly.py	95.19%	0 Missing and 5 partials ⚠️

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@@            Coverage Diff             @@
##           master    #1779      +/-   ##
==========================================
+ Coverage   95.66%   95.84%   +0.17%     
==========================================
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cadquery/assembly.py

…mport

jmwright · 2025-04-22T16:11:31Z

@adam-urbanczyk In 4045c58 you set the cadquery.Assembly.importStep method up to be a class method, and you construct assy before calling the lower-level method. However, since the Assembly.name property is private and can only be set during instantiation, this creates an issue for me. I need to be able to set the top-level assembly name based on the name set in the STEP file, which requires me to set the name property after instantiation.

We need to decide on the proper way to fix this.

adam-urbanczyk · 2025-04-22T16:26:04Z

Hey, I do not understand the issue. You can always do this:

assy = Assembly()
assy.name = '123'

Do you mean that you need to modify AssemblyProtocol to satisify mypy? That also does not sound like an issue to me.

jmwright · 2025-04-22T16:51:59Z

Correct, mypy complains. I can make that change to make name a public property if you don't see an issue with doing so.

…mport

…king through indirect lookup

…mport

…the line.

adam-urbanczyk

Thanks, 2nd pass

cadquery/assembly.py

cadquery/occ_impl/importers/assembly.py

adam-urbanczyk · 2025-07-01T17:40:59Z

cadquery/occ_impl/importers/assembly.py

+
+        # Process the color for the shape, which could be of different types
+        color = Quantity_Color()
+        cq_color = cq.Color(0.50, 0.50, 0.50)


What are the magic parameters?

They are the RGB values that most of the CQ visualization methods seem to be using as a default with assemblies (gray/silver). The values are not standardized as cadquery.vis.show seems to use a gold color IIRC. CQ-editor uses the gray color though.

OK, default color should be None. See:

class Assembly(object): """Nested assembly of Workplane and Shape objects defining their relative positions.""" loc: Location name: str color: Optional[Color] metadata: Dict[str, Any] obj: AssemblyObjects parent: Optional["Assembly"] children: List["Assembly"] objects: Dict[str, "Assembly"] constraints: List[Constraint]

adam-urbanczyk · 2025-07-01T17:43:53Z

cadquery/occ_impl/importers/assembly.py

+                loc=cq.Location(parent_location),
+            )
+        else:
+            assy.add(cq.Shape.cast(shape), name=name, color=cq_color)


Why isn't this covered. Is parent location not optional?

cadquery/occ_impl/importers/assembly.py

adam-urbanczyk · 2025-07-01T17:48:27Z

cadquery/occ_impl/importers/assembly.py

+                # Pass down the location or other context as needed
+                # Add the parent location if it exists
+                if parent_location is not None:
+                    loc = parent_location * loc


Isn't this suspicious. Assy applies locations in a relative sense. It shouldn't be needed to construct absolute locations.

I'll have to check, but I think I added this because of nested sub-assemblies

Confirmed. If the parent location is not passed through the call stack, nested subassemblies will break. I added the test_nested_subassembly_step_import test to illustrate this. If you disable parent location passing and run that test, it should fail.

OK, but that is actually suspicious. When you construct an assy you do not need combine (i.e. multiply) the locations explicitly.

lorenzncode · 2025-07-06T19:03:08Z

I am still getting a ValueError with a STEP from the tests.

(cqdev) lorenzn@fedora:~/devel/cadquery$ git status -u no
On branch assembly-import
Your branch is up to date with 'upstream/assembly-import'.

nothing to commit, working tree clean
(cqdev) lorenzn@fedora:~/devel/cadquery$ pytest tests/test_assembly.py --basetemp=./tmp2 -k test_colors_assy1 -q --no-summary
...........                                                                                                                                                        [100%]
11 passed, 96 deselected, 13 warnings in 0.58s
sys:1: DeprecationWarning: builtin type swigvarlink has no __module__ attribute
(cqdev) lorenzn@fedora:~/devel/cadquery$ cat test2.py 
from cadquery import Assembly

obj = Assembly.importStep("./tmp2/assembly10/chassis0_assy.step")
(cqdev) lorenzn@fedora:~/devel/cadquery$ python test2.py 
Traceback (most recent call last):
  File "/home/lorenzn/devel/cadquery/test2.py", line 3, in <module>
    obj = Assembly.importStep("./tmp2/assembly10/chassis0_assy.step")
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/lorenzn/devel/cadquery/cadquery/assembly.py", line 622, in importStep
    _importStep(assy, path)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 194, in importStep
    process_label(labels.Value(1))
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 173, in process_label
    process_label(sub_label, loc, name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 149, in process_label
    process_label(ref_label, parent_location, parent_name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 173, in process_label
    process_label(sub_label, loc, name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 149, in process_label
    process_label(ref_label, parent_location, parent_name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 173, in process_label
    process_label(sub_label, loc, name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 149, in process_label
    process_label(ref_label, parent_location, parent_name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 173, in process_label
    process_label(sub_label, loc, name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 149, in process_label
    process_label(ref_label, parent_location, parent_name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 179, in process_label
    _process_simple_shape(label, parent_location, parent_name)
  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/importers/assembly.py", line 74, in _process_simple_shape
    assy.add(
  File "/home/lorenzn/devel/cadquery/cadquery/assembly.py", line 241, in add
    self.add(assy)
  File "/home/lorenzn/devel/cadquery/cadquery/assembly.py", line 222, in add
    raise ValueError("Unique name is required")
ValueError: Unique name is required

adam-urbanczyk · 2025-07-22T06:31:07Z

@jmwright any updates on this PR?

jmwright · 2025-07-22T12:10:19Z

@adam-urbanczyk Not yet. I got busy with some other things.

…mport

jmwright · 2025-07-28T14:18:09Z

@adam-urbanczyk I'm getting mypy errors now that I did not before. Most of them are probably my fault, but there is this one about the OpenCASCADE code.

cadquery\occ_impl\importers\assembly.py:105: error: "TDF_Attribute" has no attribute "GetFather"  [attr-defined]

Does this have anything to do with the stubs being published as part of OCP 7.9.x?

adam-urbanczyk · 2025-07-28T17:03:16Z

Nothing should be published, but let me check

jmwright · 2025-07-29T00:56:45Z

I'm having trouble with mypy. It is giving me different errors locally than I get in CI even though I have the same version. I'll create a new environment from scratch tomorrow and try to match the CI environment to see if I can get rid of the discrepancies.

…code out of loop

… a contrived STEP file

jmwright · 2025-07-30T20:47:36Z

@adam-urbanczyk @lorenzncode Please have another look when you get a chance. This PR has been significantly reworked, and a test or two added.

adam-urbanczyk · 2025-08-04T05:58:49Z

Something is off with top level location handling.

Before importing:

After importing:

Code:

#%% imports
from cadquery import Assembly, Location, Color, importers
from cadquery.func import box, rect, sphere
from cadquery.vis import show

#%% prepare the model
def make_model(name: str, COPY: bool):
    b = box(1,1,1)
    
    assy_top = Assembly(name='test_assy_top', loc=Location((0,1,1)))
    assy_top.add(sphere(1))
    
    assy = Assembly(name='test_assy', loc=Location((5,5,1)))
    assy.add(box(1,2,5), color=Color('green'))
    
    
    
    for v in rect(10,10).vertices():
        assy.add(
            b.copy() if COPY else b,
            loc=Location(v.Center()),
            color=Color('red')
        )
        
    # show(assy)
    assy_top.add(assy)
    assy_top.export(name)
    
    return assy_top

assy = make_model("test_assy.step", False)

show(assy, Location(),  scale=5)

#%% import the assy without copies - this throws

assy_i = Assembly.importStep("test_assy.step")
wp = importers.importStep("test_assy.step")

show(assy_i, Location(),scale=5)

jmwright · 2025-08-04T17:58:53Z

@adam-urbanczyk Thanks, I fixed that bug and modified one of the tests so that I could add an assert to verify.

lorenzncode

Thanks for the big effort @jmwright! The error I had before is resolved now when I try importing from the pytest generated step file.

I find import/export round trip changes the assembly as follows. Is this expected?

from cadquery import Assembly, Location
from cadquery.func import box


def round_trip_test(assy, n=3):
    for i in range(n):
        print(f"\n{i=}")
        for name in assy._flatten().keys():
            print(name)
        assy.export(f"out{i}.step")
        assy = Assembly.importStep(f"out{i}.step")


b = box(1, 1, 1)
assy = Assembly(name="assy")
assy.add(b, name="box0")
assy.add(b, name="box1", loc=Location((1, 0, 0)))

round_trip_test(assy, 5)

i=0
assy/box0
assy/box1
assy

i=1
assy/box0/box0_part
assy/box0
assy/box1/box0_part
assy/box1
assy

i=2
assy/box0/box0_part/box0_part_part
assy/box0/box0_part
assy/box0
assy/box1/box0_part/box0_part_part
assy/box1/box0_part
assy/box1
assy

i=3
assy/box0/box0_part/box0_part_part/box0_part_part_part
assy/box0/box0_part/box0_part_part
assy/box0/box0_part
assy/box0
assy/box1/box0_part/box0_part_part/box0_part_part_part
assy/box1/box0_part/box0_part_part
assy/box1/box0_part
assy/box1
assy

i=4
assy/box0/box0_part/box0_part_part/box0_part_part_part/box0_part_part_part_part
assy/box0/box0_part/box0_part_part/box0_part_part_part
assy/box0/box0_part/box0_part_part
assy/box0/box0_part
assy/box0
assy/box1/box0_part/box0_part_part/box0_part_part_part/box0_part_part_part_part
assy/box1/box0_part/box0_part_part/box0_part_part_part
assy/box1/box0_part/box0_part_part
assy/box1/box0_part
assy/box1
assy

lorenzncode · 2025-08-08T23:42:28Z

tests/test_assembly.py

+    assy = subshape_assy()
+
+    # Use a temporary directory
+    tmpdir = tmp_path_factory.mktemp("out")


FYI, you could use the tmpdir fixture (line 42) to reduce boilerplate.

lorenzncode · 2025-08-08T23:47:39Z

tests/test_assembly.py

+    tmpdir = tmp_path_factory.mktemp("out")
+    plain_step_path = os.path.join(tmpdir, "plain_assembly_step.step")
+
+    # Simple cubes


There are existing assembly fixtures that could be used here (and for other tests) instead. OK if you would rather explicitly redefine here.

adam-urbanczyk · 2025-08-09T07:55:03Z

Thanks for the big effort @jmwright! The error I had before is resolved now when I try importing from the pytest generated step file.

I find import/export round trip changes the assembly as follows. Is this expected?

That is definitely not OK.

adam-urbanczyk · 2025-08-09T08:01:56Z

cadquery/occ_impl/importers/assembly.py

+                    else:
+                        cq_color = None
+
+                    new_assy.add(


So probably some logic should be added here to handle the name / name_part pairs. E.g. something like:

if ref_name.endswith('_part') and ref_name.startswith(parent_name): new_assy[parent_name].obj = cq_shape else: ...

CC @lorenzncode

adam-urbanczyk · 2025-08-09T08:03:33Z

tests/test_assembly.py

+    assert assy.children[0].name == "cube_1"
+    assert assy.children[1].children[0].name == "cylinder_1"
+
+
 @pytest.mark.parametrize(


Probably a test that asserts idempotence of export/import is also needed.

jmwright added 4 commits February 26, 2025 11:32

Initial commit with colors and locations working for simple assemblies

821aa1e

Trying to fix mypy error

c3d5573

Jumping through hoops to make mypy happy

da9844a

Lint fix

7b674c8

adam-urbanczyk reviewed Feb 27, 2025

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cadquery/assembly.py Outdated Show resolved Hide resolved

jmwright and others added 8 commits February 27, 2025 08:51

Refactored method interface based on suggestion

288c0a0

Use Self and @classmethod

4045c58

Lint fix

d708acd

Merge branch 'master' of github.com:CadQuery/cadquery into assembly-i…

aa09d31

…mport

Added a test specifically for testing metadata

f88ad35

Merging master and fixing conflicts

6493135

Seeing if coverage and tests will pass

e51a7cb

Added name loading from STEP file

36d7035

jmwright added 13 commits April 22, 2025 12:59

Made name a public property of Assembly

f29056e

Merge branch 'master' of github.com:CadQuery/cadquery into assembly-i…

14e002b

…mport

Trying to increase test coverage a bit

687bc2b

Syncing up some experiments

6b360c2

Merge branch 'master' of github.com:CadQuery/cadquery into assembly-i…

73f007e

…mport

Got color and layer search working, still need to get name search wor…

5e19332

…king through indirect lookup

Got tests working for layer and color info import

5f4c4c2

Got shape name loading to work

e5bccb2

Trying to get approximate tuple comparison working

d5bc317

Black fix

9b48507

Added a test for a bad filename, and added a custom color

65f38c8

Merge branch 'master' of github.com:CadQuery/cadquery into assembly-i…

54e23ee

…mport

Increase test coverage a bit and improve color name check

2810bc2

Removed a stray import that was probably added by AI somewhere along …

c85ec9c

…the line.

adam-urbanczyk requested changes Jul 1, 2025

View reviewed changes

jmwright added 2 commits July 2, 2025 15:42

Implement some of the suggestions

46c84c6

Added a test for nested subassemblies on import

c75d0c8

jmwright added 4 commits July 24, 2025 10:09

Merge branch 'master' of github.com:CadQuery/cadquery into assembly-i…

d0714fd

…mport

Rework which covers everything except subshapes and layers

d69856a

Added layer name support back in

c8e0c08

Added a round-trip test and fixed issues that it revealed

7639fdf

jmwright added 3 commits July 28, 2025 15:55

mypy fixes

eedc16f

More mypy fixes

ee2b834

Missed a cast

2b8a8eb

jmwright added 4 commits July 29, 2025 17:47

More mypy fixes

c7821ee

Tried to remove the attribute iterator and could not, but moved some …

f88aa9a

…code out of loop

Fixes and simplifications based on codecov checks

71e309a

More cleanup to try to get code coverage high enough without creating…

7da1eab

… a contrived STEP file

jmwright added 2 commits August 4, 2025 11:32

Fix lack of application to the top-level assembly

8251d92

Trying to increase test coverage high enough

1543908

lorenzncode reviewed Aug 9, 2025

View reviewed changes

adam-urbanczyk reviewed Aug 9, 2025

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Add STEP Import for Assemblies #1779

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