PyBMesh

Homepage: https://gitlab.com/alexis.sauvageon/pybmesh

PyBMesh is a Python library for generating, manipulating, and exporting meshes using VTK. It supports a wide range of mesh types - from points (0D) to volumes (3D) - and provides advanced tools such as extrusion (both linear and rotational), mesh fusion, and boundary extraction. PyBMesh is designed to help users create high-quality meshes for computational simulations and CFD applications (e.g., for OpenFOAM).

Prerequisites

• C Compiler (GCC or Clang)
• C++ Compiler (GCC or MSVC 14.0+)

Windows

Microsoft Visual C++ 14.0 or greater is required. Get it with "Microsoft C++ Build Tools":
Download Microsoft C++ Build Tools

Linux

Install GCC and related build tools via your package manager:

sudo apt-get update
sudo apt-get install build-essential

Installation

Install PyBMesh from pypi.org using pip: pip install pybmesh

Or clone the repository and install with: python pip install -e .

Module Structure

A high-level view of the project layout:

+-- examples/             # Example scripts illustrating common meshing workflows.
+-- LICENSE               # MIT License.
+-- pybmesh/              # Main package.
¦   +-- cython/         # Cython modules for performance-critical tasks.
¦   +-- geom/           # Definitions for 0D (points), 1D (lines, arcs, circles), 2D (surfaces), and 3D (volumes) elements.
¦   +-- io/             # I/O routines for VTK conversion and mesh writing.
¦   +-- utils/          # Utility modules including mesh manipulation tools (fusion, extrusion, boundary extraction).
+-- pyproject.toml        # Build configuration.
+-- README.md             # This documentation.
+-- ressources/           # other useful files.
+-- tests/                # Unit tests for verifying functionality.

Quick Tutorial

Creating Basic Mesh Elements

PyBMesh provides classes for each mesh dimension:

• 0D - Points:

from pybmesh import Point
p = Point(0, 0, 0)

• 1D - Lines, Arcs, and Circles:

from pybmesh import Point, Line, Arc, Circle
p1 = Point(0, 0, 0)
p2 = Point(1, 0, 0)
line = Line(p1, p2, n=10)

# Create an arc using a center and boundary points:
arc = Arc.from_center_2points(center=p1.coords[0], pA=p2.coords[0],
                               pB=Point(0, 1, 0).coords[0], n=10)``

• 2D - Surfaces:

from pybmesh import Surface
p3 = Point(1, 1, 0)
p4 = Point(0, 1, 0)
surface = Surface(p1, p2, p3, p4, n=1, quad=True)` 

• 3D - Volumes:

from pybmesh import Volume, translate
surface2 = surface.copy()
surface2.translate(0, 0, 1)
volume = Volume(surface, surface2, n=10)

Mesh Manipulation

The pybmesh.utils.meshtools module offers several functions for transforming and combining meshes:

from pybmesh import translate, rotate, syme, scale, fuse

• Translate a mesh (with copy):

translated = translate(surface, (2, 0, 0))

• Rotate 90° about the Z-axis (with copy):

rotated = rotate(surface, center=(0,0,0), axis=(0,0,1), angle=90)

• Reflect (symmetry) across the XY-plane (with copy):

reflected = syme(surface, plane='xy')

• Scale a mesh (with copy):

scaled = scale(surface, sx=2, sy=1, sz=1)

• Fuse two meshes:

fused = fuse(surface, translated)` 

Extruding Meshes

Create higher-dimensional meshes via extrusion:

• Linear Extrusion:

from pybmesh.meshmanip import extrudeLinear
vector_line = Line(Point(0,0,0), Point(0,0,1), n=1)
extruded_surface = extrudeLinear(line, vector_line)` 

• Rotational Extrusion:

from pybmesh.meshmanip import extrudeRotational
rot_extruded = extrudeRotational(line, pA=(0,0,0), pB=(0,0,1), angle=45, n=10)` 

Additional Tools

• Boundary Extraction:
  Use getBoundaries from pybmesh.meshmanip to extract faces, edges, or nodes from a mesh.

• Submesh Extraction:
  Use extract_point and extract_element functions for obtaining submeshes based on criteria.

• Assembly and Export:
  Combine mesh components using MeshComponent and MeshAssembly, and export meshes using VTK writers (e.g., in FoamSave.py).

Examples

The examples/ directory contains scripts that illustrate various workflows:

• Lines.py: Demonstrates creation and manipulation of 1D elements.
• Surfaces.py: Shows surface generation from curves and transfinite techniques.
• Volumes.py: Illustrates volume creation by interpolating between surfaces.
• Extrude_Exemples.py: Provides examples of linear and rotational extrusion.
• Extract_Boundaries.py & Extract_submeshes.py: Demonstrate boundary and submesh extraction.
• FoamSave.py: Exports meshes to VTK files for CFD applications.
• MeshComponent.py & MeshAssembly.py: Show how to build a complete mesh from components.

Help and Documentation

For complete descriptions of classes and functions, use Python's built-in help. For example, to view details about the Volume class:

from pybmesh import Volume
help(Volume)` 

This will print a full explanation of the constructor, methods, and usage examples.

License

PyBMesh is released under the BSD 3-Clause License(LICENSE).