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In [7]:

import numpy as np
import scipy
import matplotlib.pyplot as plt

import numpy as np import scipy import matplotlib.pyplot as plt

In [8]:

path = "./data/p1_swanPolygon.txt"
boundaries = np.loadtxt(path, delimiter='\t') # (x, y) pairs

path = "./data/p1_swanPolygon.txt" boundaries = np.loadtxt(path, delimiter='\t') # (x, y) pairs

In [29]:

plt.fill(boundaries[:,0], boundaries[:,1], 'gray')
plt.gca().axis('equal')
plt.show()

plt.fill(boundaries[:,0], boundaries[:,1], 'gray') plt.gca().axis('equal') plt.show()

In [70]:

def triangle_mesh(boundaries):
    x_max, x_min = np.max(boundaries[:,0]), np.min(boundaries[:,0])
    y_max, y_min = np.max(boundaries[:,1]), np.min(boundaries[:,1])    
    vertices = np.array([[x_min - 1, y_min - 1],
                         [x_min - 1, y_max + 1],
                         [x_max + 1, y_min - 1],
                         [x_max + 1, y_max + 1]])
    vertices = np.concatenate((vertices, boundaries), axis=0)
    tri = scipy.spatial.Delaunay(vertices).simplices
    tri = tri[np.all(tri > 4, axis=1)]
    vertices = vertices[4:]
    tri = tri - 4
    return vertices, tri

def triangle_mesh(boundaries): x_max, x_min = np.max(boundaries[:,0]), np.min(boundaries[:,0]) y_max, y_min = np.max(boundaries[:,1]), np.min(boundaries[:,1]) vertices = np.array([[x_min - 1, y_min - 1], [x_min - 1, y_max + 1], [x_max + 1, y_min - 1], [x_max + 1, y_max + 1]]) vertices = np.concatenate((vertices, boundaries), axis=0) tri = scipy.spatial.Delaunay(vertices).simplices tri = tri[np.all(tri > 4, axis=1)] vertices = vertices[4:] tri = tri - 4 return vertices, tri

In [72]:

vertices, tri = triangle_mesh(boundaries)
plt.plot(vertices[:,0], vertices[:,1], 'o')
plt.triplot(vertices[:,0], vertices[:,1], tri)

vertices, tri = triangle_mesh(boundaries) plt.plot(vertices[:,0], vertices[:,1], 'o') plt.triplot(vertices[:,0], vertices[:,1], tri)

Out[72]:

[<matplotlib.lines.Line2D at 0x7efbaa6221d0>,
 <matplotlib.lines.Line2D at 0x7efbaa97e950>]

In [54]:

plt.triplot(vertices[:,0], vertices[:,1], lines)
plt.gca().axis('equal')

plt.triplot(vertices[:,0], vertices[:,1], lines) plt.gca().axis('equal')

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[54], line 1
----> 1 plt.triplot(vertices[:,0], vertices[:,1], lines)
      2 plt.gca().axis('equal')

File ~/Source/tiankaima/Notebooks/venv/lib/python3.11/site-packages/matplotlib/pyplot.py:4021, in triplot(*args, **kwargs)
   4019 @_copy_docstring_and_deprecators(Axes.triplot)
   4020 def triplot(*args, **kwargs):
-> 4021     return gca().triplot(*args, **kwargs)

File ~/Source/tiankaima/Notebooks/venv/lib/python3.11/site-packages/matplotlib/tri/_triplot.py:40, in triplot(ax, *args, **kwargs)
      8 """
      9 Draw an unstructured triangular grid as lines and/or markers.
     10 
   (...)
     36     The drawn marker nodes.
     37 """
     38 import matplotlib.axes
---> 40 tri, args, kwargs = Triangulation.get_from_args_and_kwargs(*args, **kwargs)
     41 x, y, edges = (tri.x, tri.y, tri.edges)
     43 # Decode plot format string, e.g., 'ro-'

File ~/Source/tiankaima/Notebooks/venv/lib/python3.11/site-packages/matplotlib/tri/_triangulation.py:167, in Triangulation.get_from_args_and_kwargs(*args, **kwargs)
    164 else:
    165     x, y, triangles, mask, args, kwargs = \
    166         Triangulation._extract_triangulation_params(args, kwargs)
--> 167     triangulation = Triangulation(x, y, triangles, mask)
    168 return triangulation, args, kwargs

File ~/Source/tiankaima/Notebooks/venv/lib/python3.11/site-packages/matplotlib/tri/_triangulation.py:80, in Triangulation.__init__(self, x, y, triangles, mask)
     75         raise ValueError(
     76             'triangles are indices into the points and must be in the '
     77             f'range 0 <= i < {len(self.x)} but found value '
     78             f'{self.triangles.max()}')
     79     if self.triangles.min() < 0:
---> 80         raise ValueError(
     81             'triangles are indices into the points and must be in the '
     82             f'range 0 <= i < {len(self.x)} but found value '
     83             f'{self.triangles.min()}')
     85 # Underlying C++ object is not created until first needed.
     86 self._cpp_triangulation = None

ValueError: triangles are indices into the points and must be in the range 0 <= i < 87 but found value -3

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