def triangulate_regions(regions):
"""
Processes a set of regions (non-overlapping polygons tiling a portion of the plane),
triangulating any region that is not already a triangle, and storing triangulated
relationships in a DAG.
Arguments:
regions -- a set of non-overlapping polygons that tile some part of the plane
Returns: a triangulation for each individual region in 'regions'
"""
frontier = []
for region in regions:
self.dag.add_node(region)
# If region is not a triangle, triangulate
if region.n > 3:
triangles = spatial.triangulatePolygon(region)
for triangle in triangles:
# Connect DAG
self.dag.add_node(triangle)
self.dag.connect(triangle, region)
# Add to frontier
frontier.append(triangle)
else:
frontier.append(region)
return frontier
def add_bounding_triangle(poly):
"""
Calculates a bounding triangle for a polygon
Arguments:
poly -- a polygon to-be bound
Returns: a bounding polygon for 'poly'
"""
bounding_tri = min_triangle.boundingTriangle(poly.points)
bounding_regions = spatial.triangulatePolygon(
bounding_tri, hole=poly.points)
return bounding_tri, bounding_regions
def remove_independent_set(regions):
"""
Processes a set of regions, detecting and removing an independent set
of vertices from the regions' graph representation, and re-triangulating
the resulting holes.
Arguments:
regions -- a set of non-overlapping polygons that tile some part of the plane
Returns: a new set of regions covering the same subset of the plane, with fewer vertices
"""
# Take note of which points are in which regions
points_to_regions = {}
for idx, region in enumerate(regions):
for point in region.points:
if point in points_to_regions:
points_to_regions[point].add(idx)
continue
points_to_regions[point] = set([idx])
# Connect graph
g = UndirectedGraph()
for region in regions:
for idx in range(region.n):
u = region.points[idx % region.n]
v = region.points[(idx + 1) % region.n]
if not g.contains(u):
g.add_node(u)
if not g.contains(v):
g.add_node(v)
g.connect(u, v)
# Avoid adding points from outer triangle
removal = g.independent_set(8, avoid=bounding_triangle.points)
# Track unaffected regions
unaffected_regions = set([i for i in range(len(regions))])
new_regions = []
for p in removal:
# Take note of affected regions
affected_regions = points_to_regions[p]
unaffected_regions.difference_update(points_to_regions[p])
def calculate_bounding_polygon(p, affected_regions):
edges = []
point_locations = {}
for j, i in enumerate(affected_regions):
edge = set(regions[i].points)
edge.remove(p)
edges.append(edge)
for v in edge:
if v in point_locations:
point_locations[v].add(j)
else:
point_locations[v] = set([j])
boundary = []
edge = edges.pop()
for v in edge:
point_locations[v].remove(len(edges))
boundary.append(v)
for k in range(len(affected_regions) - 2):
v = boundary[-1]
i = point_locations[v].pop()
edge = edges[i]
edge.remove(v)
u = edge.pop()
point_locations[u].remove(i)
boundary.append(u)
return shapes.Polygon(boundary)
# triangulate hole
poly = calculate_bounding_polygon(p, affected_regions)
triangles = spatial.triangulatePolygon(poly)
for triangle in triangles:
self.dag.add_node(triangle)
for j in affected_regions:
region = regions[j]
self.dag.connect(triangle, region)
new_regions.append(triangle)
for i in unaffected_regions:
new_regions.append(regions[i])
return new_regions
def testRandomTriangles(self):
poly = randomConvexPolygon(50)
regions = triangulatePolygon(poly)
self.runLocator(regions)
