### Error: Sorry this triangulation does not deal with intersecting constraints

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10 weeks ago by
I'm trying to create a mesh like the filled-in Koch-curve by adding triangles and then generating a mesh. Please see below. There is no boundary supposed to be in-between.

from dolfin import *
from mshr import *
import math

def dist(p1, p2):
return sqrt(pow(p2.x() - p1.x(), 2) + pow(p2.y() - p1.y(), 2))

def findLowerMiddlePoint(p1, p2):
return Point(p1.x() + (p2.x() - p1.x()) * 1/3, p1.y() + (p2.y() - p1.y()) * 1/3)

def findUpperMiddlePoint(p1, p2):
return Point(p1.x() + (p2.x() - p1.x()) * 2/3, p1.y() + (p2.y() - p1.y()) * 2/3)

def findThirdPoint(p1, p2):
dx = p2.x() - p1.x()
dy = p2.y() - p1.y()
alpha = 60./180 * pi

x3 = p1.x() + math.cos(alpha) * dx + math.sin(alpha) * dy
y3 = p1.y() + math.sin(-alpha) * dx + math.cos(alpha) * dy

return Point(x3, y3)

def orderCCW(p1, p2, p3):
val = (p2.y() - p1.y()) * (p3.x() - p2.x()) - (p2.x() - p1.x()) * (p3.y() - p2.y())
if val > 0: return [p1, p3, p2]
else: return [p1, p2, p3]

# Create geometry

polygons = Polygon([Point(10,10), Point(10,10.01), Point(9.99,10)])

def createKochCurve(p1, p2, d):
if d == 0: return 0

lmp = findLowerMiddlePoint(p1, p2)
ump = findUpperMiddlePoint(p1, p2)

thp = findThirdPoint(lmp, ump)

newpoly = Polygon(orderCCW(lmp, ump, thp))
print(lmp.x(), lmp.y())

global polygons
polygons += newpoly

createKochCurve(lmp, thp, d-1)
createKochCurve(ump, thp, d-1)

pstart = Point(0, 0)
pend = Point(1, 0)
depth = 2

createKochCurve(pstart, pend, depth)

mesh = generate_mesh(polygons,100)

Message:

sorry, this triangulation does not deal with
intersecting constraints
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range
[0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
[0]PETSC ERROR: or see http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
[0]PETSC ERROR: or try http://valgrind.org on GNU/linux and Apple Mac OS X to find memory corruption errors
[0]PETSC ERROR: configure using --with-debugging=yes, recompile, link, and run