ocp-gordon 0.1.5

A Python library for Gordon Surface interpolation using B-splines.

Gordon Surface Library for CadQuery's OCP

This library provides a Python implementation for creating Gordon surfaces, a method for interpolating a network of curves to generate a smooth surface. It is designed to be compatible with CadQuery's OCP and leverages B-spline mathematics.

The implementation is written entirely in Python and is adapted from the original C++ code in occ_gordon

Features

• Gordon surface interpolation from profile and guide curves.
• Compatibility with B-spline representations.
• Integration with CadQuery's OCP (OpenCASCADE Python) for geometric primitives.

Installation

This package can be installed using pip.

pip install ocp_gordon

Dependencies

• OCP (OpenCASCADE Python)
• NumPy
• SciPy

Usage

Here's a basic example of how to use the library:

# Assume you have profile_curves and guide_curves defined as lists of B-spline objects
# profile_curves = [...] # List of Geom_BSplineCurve objects
# guide_curves = [...]   # List of Geom_BSplineCurve objects

from ocp_gordon import interpolate_curve_network

gordon_surface = interpolate_curve_network(profile_curves, guide_curves, tolerance=0.0003)

For more detailed examples, please refer to the examples/ directory in the source code.

Test

To run tests, first install pytest, then:

cd tests
python test_all.py

Notable Difference from C++ Code

• In intersect_bsplines.py, a polyfilled math_BFGS is used instead of math_FRPR. Both math_BFGS and math_FRPR are not usable in OCP because OCP does not expose math_Vector. The activate() function in this file has also been changed since the original one does not work well. In IntersectBSplines function, first check if the intersection occurs at the end points before using 2d minimizer.
• In the _solve() function in bspline_approx_interp.py, the regularization is added to prevent singular matrix which occurs in some cases for example when the input curve is a bspline converted from a circle.
• A new file misc.py is added to implement some missing classes/functions from OCP. The major ones are clone_bspline and math_BFGS.

Caveats

• In the IntersectBSplines function, the 2d minimizer does not work well when the number of profile/guides is high (>5). Increase the tolerance parameter in interpolate_curve_network can help.

License

This project is licensed under the Apache 2.0 License - see the LICENSE file for details.

Citing

The algorithm was originally described in:

Siggel M. et. al. (2019), TiGL: An Open Source Computational Geometry Library for Parametric Aircraft Design

@article{siggel2019tigl,
	title={TiGL: an open source computational geometry library for parametric aircraft design},
	author={Siggel, Martin and Kleinert, Jan and Stollenwerk, Tobias and Maierl, Reinhold},
	journal={Mathematics in Computer Science},
	volume={13},
	number={3},
	pages={367--389},
	year={2019},
	publisher={Springer},
    doi={10.1007/s11786-019-00401-y}
}