HullProd

Geometry-based producibility screening for ship hull surfaces.

HullProd computes a compact signature of double-curvature intensity, sign, and areal composition directly from native IGES/STEP BRep geometry or triangulated STL/OBJ/PLY surfaces. It also exports distributed fields, plots, validity, and representation provenance.

Installation

HullProd requires Python 3.10–3.12. The intended public installation command is:

pip install hullprod

One installation includes both the native OpenCascade and triangle-mesh backends; no separate CAD extra or system OpenCascade installation is required.

Quick start

Assess native CAD directly:

hullprod myvessel.iges

The same command works for a triangulated surface:

hullprod myvessel.stl

HullProd selects the backend from the file extension and writes a predictable myvessel_hullprod/ result directory.

To supply the normalization length explicitly:

hullprod myvessel.iges --lref 200000

--lref uses the working length unit of the input geometry. For CAD imported in millimetres, 200000 means 200000 mm, or 200 m. HullProd prints the source unit, working unit, and interpreted value before integration and warns about a large discrepancy from the automatic geometric span without changing the supplied value.

See Getting started for output-directory controls and other normal options.

Recommended signature

HullProd 1.0 reports exactly:

[I_D, I_D_plus, I_D_minus,
 a_C_flat, a_C_single, a_C_elliptic, a_C_saddle]

• I_D measures total normalized double-curvature intensity.
• I_D_plus and I_D_minus separate elliptic/synclastic and saddle/reverse/anticlastic intensity.
• The four a_C values are represented-valid-area fractions for flat, singly curved, elliptic, and saddle/reverse regions.

Together they describe intensity, sign, and areal extent. HullProd does not combine them into a universal scalar producibility score. The default quasi-zero factors are h_f = k_f = 1e-4; these are numerical classification thresholds, not manufacturing limits. See Metrics for the equations and interpretation.

What HullProd produces

A normal result directory contains:

• signature.json and signature.csv for the recommended global signature;
• report.html for a compact, static user report;
• validity.json and provenance.json for scientific interpretation and audit;
• plots/ with developability-density and curvature-class maps; and
• fields/ with ParaView-readable VTP and portable CSV surface fields.

The complete output contract and file roles are documented in Outputs.

Supported geometry

Unsupported formats fail with an actionable error; HullProd does not silently convert a BRep to a mesh for canonical global evaluation or fit CAD to a mesh.

BRep and mesh realizations

Native BRep evaluation is the canonical realization when source CAD is available. Its global metrics come from direct surface derivatives and trimmed-domain integration, not from the display/export tessellation.

Mesh evaluation is supported when triangulated geometry is the available representation. Its derivative-based values are explicitly representation-sensitive and should be interpreted with the recorded mesh quality and refinement provenance. This distinction does not make mesh results invalid; it makes their represented geometry part of the result.

Without --lref, both backends use the same conceptual automatic convention: a rigid-motion-invariant principal-axis projected span, with a deterministic centroid-radial fallback for isotropic samples. It is recorded as auto_principal_span and is never described as L_pp.

Python API

The Python API uses the same assessment pipeline as the CLI:

from hullprod import assess

result = assess("myvessel.iges")
print(result.signature)

See the Python API guide.

Documentation

• Getting started
• Recommended metrics
• Result files and field exports
• Validity and provenance
• Python API
• Experimental quantities
• Release history

README plus versioned Markdown under docs/ are the complete v1 documentation system; no hosted documentation site is required.

Scientific scope and limitations

HullProd is a geometry-based early-design screening tool, not a fabrication-cost predictor. It does not directly predict labor, forming route, production schedule, or shipyard-specific performance. It does not perform panelization, seam placement, forming simulation, optimization, or geometry repair.

Auxiliary, mesh-diagnostic, and experimental quantities are kept separate from the recommended signature. Their status is explained in Experimental quantities.

Funding

Development of HullProd was supported by the U.S. Office of Naval Research (ONR) through the Naval International Cooperative Opportunities in Science and Technology (NICOP) program, under Grant No. N00014-26-1-2164, as part of the BEAM project (Bayesian Exploration and Optimization for Hull-form Architecture and Producibility Modeling).

The views and conclusions expressed in this software and its documentation are those of the authors and do not necessarily reflect the views of the Office of Naval Research.

Citation

Please cite the software using CITATION.cff. Cite the associated manuscript once final publication metadata are available; no DOI or journal record is claimed here before publication.

Contributing

Bug reports, documentation corrections, reproducible analytical tests, and carefully scoped numerical improvements are welcome. See CONTRIBUTING.md before proposing changes to scientific definitions.

License

HullProd is distributed under the BSD-3-Clause license. The bundled analytical sphere fixtures are project-owned; restricted benchmark geometry is not redistributed.