def init_mesh(self, n=2, meshtype='tri'):
""" generate the initial mesh
"""
node = np.array([(0, 0), (1, 0), (1, 1), (0, 1)], dtype=np.float)
cell = np.array([(1, 2, 0), (3, 0, 2)], dtype=np.int)
mesh = TriangleMesh(node, cell)
mesh.uniform_refine(2)
threshold = lambda p: (p[:, 0] > 0.25) & (p[:, 0] < 0.75) & (
p[:, 1] > 0.25) & (p[:, 1] < 0.75)
mesh.delete_cell(threshold)
mesh.uniform_refine(n=n)
return mesh
from fealpy.mesh import TriangleMesh
from fealpy.mesh.simple_mesh_generator import distmesh2d
from fealpy.mesh.level_set_function import drectangle
import triangle as tri
from scipy.spatial import Delaunay
box = [0, 1, 0, 1]
pfix = np.array([[0.0, 0.0], [1.0, 0.0], [1.0, 1.0], [0.0, 1.0]],
dtype=np.float)
fd = lambda p: drectangle(p, box)
bbox = [-0.1, 1.1, -0.1, 1.1]
pmesh = distmesh2d(fd, 0.01, box, pfix, meshtype='polygon')
fig = plt.figure()
axes = fig.gca()
pmesh.add_plot(axes)
node = pmesh.entity('node')
t = Delaunay(node)
tmesh = TriangleMesh(node, t.simplices.copy())
area = tmesh.entity_measure('cell')
tmesh.delete_cell(area < 1e-8)
area = tmesh.entity_measure('cell')
fig = plt.figure()
axes = fig.gca()
tmesh.add_plot(axes)
plt.show()
