cq-acis 0.1.0

ACIS SAT/SAB parsing experiments for CadQuery

cq-acis

Parse ACIS SAT/SAB data and convert the supported analytic B-rep subset to CadQuery/OpenCascade shapes.

日本語版: README.ja.md

This project is experimental. ACIS SAT versions and producer-specific records vary, so unsupported entities are preserved as raw records and conversion fails explicitly when an exact shape cannot be built.

Features

• SAT container detection and ASCII record framing
• Legacy one-line and modern three-line SAT headers
• Counted @<length> strings used by SAT 7 and later
• SAB and Autodesk ShapeManager SAB preamble detection
• Entity-reference graph validation for $n pointers
• Typed decoding for SAT save versions 105, 400, 600, and 700
• Typed topology and analytic geometry entities: body, lump, shell, face, loop, coedge, edge, vertex, point, straight-curve, ellipse-curve, plane-surface, cone-surface, and transform
• Exact CadQuery conversion for line, circular/elliptical edge, plane, cylindrical, and circular-conical geometry
• Splitting of non-manifold ACIS shells into valid CadQuery solids and compounds
• Preservation of unsupported records as RawEntity

Elliptical cones, elliptical cylinders, sheared placements, and unsupported surface/curve types are rejected rather than approximated.

Installation

The CadQuery converter is installed with the default dependencies:

python -m pip install cq-acis

For a source checkout:

python -m pip install -e .

Quick start

Parse SAT records and resolve topology references:

from cq_acis import BodyEntity, parse_sat_model

with open("model.sat", "rb") as source:
    model = parse_sat_model(source.read())

for body in model.bodies():
    assert isinstance(body, BodyEntity)
    lump = model.resolve(body.lump)
    print(body.index, lump.index if lump else None)

Convert the bodies to a CadQuery Workplane:

from cq_acis import import_sat_file

result = import_sat_file("model.sat")
shape = result.val()
assert shape.isValid()
print(shape.Volume())

Example and visual inspection

examples/parse_sat.py parses a SAT file, prints body statistics, and exports STEP, STL, and SVG files.

PYTHONPATH=src python examples/parse_sat.py
PYTHONPATH=src python examples/parse_sat.py path/to/model.sat \
  --output-dir /tmp/cq-acis-output

Open the generated STL or STEP in any 3D CAD viewer. With the optional ocp_vscode viewer installed, try:

PYTHONPATH=src python examples/parse_sat.py --show

Supported entities and conversion scope

The parser currently has typed support for:

body, lump, shell, face, loop, coedge, edge, vertex,
point, straight-curve, ellipse-curve,
plane-surface, cone-surface, transform

Typed support does not imply that every entity can already be converted to a CadQuery shape. Conversion is exact-only and raises CadQueryConversionError for unsupported geometry.

Development corpus

The pinned development corpus is not included in the Python wheel. It is kept in this repository for parser and conversion regression tests. Sources, upstream commits, and SHA-1 values are recorded in corpus/sources.lock.json; downloaded file hashes and SAT metadata are recorded in corpus/manifest.jsonl.

python scripts/fetch_corpus.py
python scripts/fetch_corpus.py --check

Review corpus/README.md and corpus/licenses/ before redistributing third-party files.

Testing

Run the full test suite from a source checkout:

PYTHONPATH=src python -m unittest discover -s tests -v

The pinned corpus currently covers 25 artifacts, including 23 SAT files and 2 SAB files. CadQuery regression tests convert 23 SAT artifacts and 147 bodies.

Project status

The package is under active development. The public API and supported SAT subset may change while broader producer/version coverage is added.

License

The project code is licensed under the MIT License. Third-party corpus files have separate notices under corpus/licenses/; consult those notices before redistribution.