landlab-triangle 0.0.2

Create unstructured Landlab grids using Jonathan Shewchuk's Triangle mesh generation software

landlab-triangle

View Landlab Documentation

View triangle Documentation

This repository adds TriangleModelGrid, a new Landlab grid type that enables unstructured triangular meshes. Unlike Landlab's standard structured grids, TriangleModelGrid allows for complex geometries with irregular boundaries, interior holes, and variable grid resolution.

Uses Jonathan Shewchuk's Triangle software.

Installation

Installing from PyPI

pip install triangle landlab-triangle

Usage

Option 1: direct initialization

from landlab_triangle import TriangleModelGrid
import numpy as np

# Create a grid directly with exterior coordinates and optional holes
exterior_y = [-1.0, -1.0, 11.0, 11.0]
exterior_x = [0.0, 10.0, 10.0, 0.0]

holes = np.array([[5.0, 5.0]])  # Optional: define interior holes

grid = TriangleModelGrid(
    exterior_y_and_x=(exterior_y, exterior_x),
    holes=holes,
    triangle_opts="pqa1Devjz"
)

print(f"Number of nodes: {grid.number_of_nodes}")
print(f"Number of cells: {grid.number_of_cells}")
print(f"Number of holes: {len(grid._holes)}")

Option 2: from a dictionary

from landlab_triangle import TriangleModelGrid

# Create a grid from a dictionary with "x" and "y" keys
grid_params = {
    "x": [0.0, 10.0, 10.0, 0.0],
    "y": [0.0, 0.0, 10.0, 10.0],
    "triangle_opts": "pqDevjz"
}

grid = TriangleModelGrid.from_dict(grid_params)

Option 3: from a shapefile

from landlab_triangle import TriangleModelGrid

# Create a grid from a shapefile, GeoJSON, or other supported format
grid = TriangleModelGrid.from_shapefile(
    "path/to/polygon.geojson",
    triangle_opts="pqDevjz",
    timeout=10
)

# The grid automatically handles holes defined in the input file
print(f"Number of holes: {len(grid._holes)}")

Triangle options

The triangle_opts parameter controls the behavior of the Triangle meshing software. Common options include:

• q: Quality mesh generation - ensures no angles smaller than N degrees (defaults to 20)
• a: Area constraint - limits the maximum area of triangles

Timeout: The timeout parameter (in seconds) prevents the meshing process from running indefinitely if Triangle encounters complex geometries.

Example with area constraint

# Create a grid with maximum triangle area of 0.1
grid = TriangleModelGrid(
    exterior_y_and_x=(exterior_y, exterior_x),
    triangle_opts="pqa0.1Devjz"  # 'a0.1' sets max area to 0.1
)