PyBezierPPM

Python interface to a parametric pinna model based on cubic Bézier curves (BezierPPM).

Requirement

Python 3.11 is required to use the software.

Installation

Get the pre-built Python wheel from the releases page and install it using pip:

$ pip install /path/to/wheel.whl

Usage

The module provides a single class BezierPPM. The constructor will generate a BezierPPM instance with default PPM-parameter values.

from bezierppm import BezierPPM

ppm = BezierPPM()

Alternatively, the PPM can be instantiated from a 'blend' file, 'csv' file, or a Python dictionary containing the PPM parameters in the same format as the 'csv' file.

Centering

Use the method center_mesh to either move the PPM's center of mass, i.e. the center of the bounding box surrounding the PPM, or the center of the ear-canal entrance to the origin of the global coordinate system.

ppm.center_mesh(reference_point='ear_canal_entrance')
ppm.center_mesh(reference_point='center_of_mass')

Parameters

To see the currently set parameters, use the print function.

print(ppm)
print(ppm.parameters['Helix up']['Start']['Location'])

Set the BezierPPM parameters using the method set_parameter.

# Scale 'Parent' (bendy bone, anisotropic scaling possible) 
ppm.set_parameter(name='Parent', type='Scale', value=(0.75, 1.5, 0.0), axis='ZXY')

# Translate 'Helix_up' (start point) 
ppm.set_parameter(name='Helix up', point='Start', type='Location', value=(1,0.6), axis='ZX')

# Rotate 'Parent' by 90 degrees around the X-axis via a quaternion
q = (np.sqrt(2)/2, np.sqrt(2)/2, 0, 0)
ppm.set_parameter(name='Parent', point='Bendy', type='Rotation', value=q, axis='WXYZ')

# Modify the shape key 'Ear_canal-Diameter'
pmod.set_parameter(name='Ear canal-Diameter', type='Shape key', value=(-1))

Export Options

The module offers the possibility to export the PPM mesh in 'stl' format using the method export_stl. The currently set PPM parameters can be exported to a 'csv' file using the method export_csv.

ppm.export_stl('ppm.stl')
ppm.export_csv('ppm.csv')

To get the points of the current PPM instance, use the method get_point_cloud or access the property 'points'.

points = ppm.get_point_cloud()
points = ppm.points

The method render can be used to render the PPM instance as 'png' and optionally 'exr' (OpenEXR) file in Blender.

ppm.render(file="/path/to/render/file/location/filename", resolution=512)

Math Helpers

The module math_helpers provides two helper functions to calculate the minimum pointwise distance and the Hausdorff distance between two PPM instances.

from bezierppm import BezierPPM
from bezierppm.math_helpers import minimal_distances, hausdorff_distance

p1 = BezierPPM()
p2 = BezierPPM(from_csv='path/to/file.csv')

# returns an array of the minimal distances between the points of p1 and p2
distances = minimal_distances(p1, p2)

# returns the hausdorff distance between the points of p1 and p2
hausdorff = hausdorff_distance(p1, p2)

Plotting Helpers

Packaged in the module, a helper function is available to visualize the PPM and the minimum pointwise distances between two PPM instances as a 3D plot and a histogram, respectively. plot_distances either accepts PPM instances or point clouds.

from bezierppm import BezierPPM
from bezierppm.plotting_helpers import plot_distances

p1 = BezierPPM()
p2 = BezierPPM(from_csv='path/to/file.csv')

plot_distances(p1, p2)

Additional Software

For the CloudCompare Blender Plugin helping to perform manual registrations please refer to the PointCloudCompare branch. For a Matlab implementation please refer to the matlab branch.

License

This software is licensed under the EUPL-1.2 License. See the LICENSE file for details.

Cite

Please cite the following paper if you use this code in your work:

• Perfler F.; Pausch F.; Pollack K.; Holighaus N.; Majdak P. (2025) Parametric model of the human pinna based on Bézier curves and concave deformations. Computers in Biology and Medicine 188: 109817. DOI: 10.1016/j.compbiomed.2025.109817.

@article{Perfler2025,
  title = {Parametric model of the human pinna based on Bézier curves and concave deformations},
  author = {Felix Perfler and Florian Pausch and Katharina Pollack and Nicki Holighaus and Piotr Majdak},
  journal = {Computers in Biology and Medicine},
  volume = {188},
  pages = {109817},
  year = {2025},
  issn = {0010-4825},
  doi = {https://doi.org/10.1016/j.compbiomed.2025.109817},
  url = {https://www.sciencedirect.com/science/article/pii/S0010482525001672},
}

References

The BezierPPM was developed at the Acoustics Research Institute (ARI) of the Austrian Academy of Sciences, Vienna, Austria [1-5].

1. Pollack K.; Pausch F.; Majdak P. (2022) Parametric pinna model for a realistic representation of listener-specific pinna geometry, Proceedings: A21, Virtual Acoustics, ICA 2022 (International Congress on Acoustics); Gyeongju, S. 168-178.
2. Pollack K.; Majdak P.; Brinkmann F.; Kreuzer W. (2021) Von Fotos zu personalisierter räumlicher Audiowiedergabe. e & i Elektrotechnik und Informationstechnik, S. 250-255.
3. Pollack K.; Majdak P. (2021) Evaluation of a Parametric Pinna Model for the Calculation of Head-Related Transfer Functions. Immersive and 3D Audio (I3DA) conference.
4. Pollack K.; Majdak P.; Furtado H. (2020) A Parametric Pinna Model for the Calculations of Head-Related Transfer Functions. Proceedings of Forum Acusticum 2020, Lyon. S. 1357-1360.
5. Perfler F.; Pausch F.; Pollack K.; Holighaus N.; Majdak P. (2025) Parametric model of the human pinna based on Bézier curves and concave deformations. Computers in Biology and Medicine, Volume 188, 2025, 109817, ISSN 0010-4825,