def test_lower_tangent_case3(self):
point_list_a = [(0, 1), (0, -1), (1, 0), (-1, 0)]
polygon_a = Polygon(point_list_a)
point_list_b = [(4, 1), (3, 3), (5, 2), (4, 4)]
polygon_b = Polygon(point_list_b)
# After polygons are created
mock_tangent_polygon_calculator = TangentPolygonCalculator()
mock_tangent_polygon_calculator['a'] = polygon_a
mock_tangent_polygon_calculator['b'] = polygon_b
expected = [Point(0, -1), Point(4, 1)]
self.assertCountEqual(
expected, mock_tangent_polygon_calculator.lower_tangent('a', 'b'))
def test_upper_tangent_case2(self):
point_list_a = [(3, 1), (4, 2), (3, 3), (2, 2)]
polygon_a = Polygon(point_list_a)
point_list_b = [(0, 1), (0, 2), (-1, 1), (-1, 2)]
polygon_b = Polygon(point_list_b)
# After polygons are created
mock_tangent_polygon_calculator = TangentPolygonCalculator()
mock_tangent_polygon_calculator['a'] = polygon_a
mock_tangent_polygon_calculator['b'] = polygon_b
expected = [Point(-1, 2), Point(3, 3)]
self.assertCountEqual(
expected, mock_tangent_polygon_calculator.upper_tangent('a', 'b'))
def convex_hull(self):
# Find midpoint
self.set_midpoint()
left = [
point for point in self.point_list if point.x <= self.midpoint.x
]
right = [
point for point in self.point_list if point.x > self.midpoint.x
]
# Divide and conquer
# Left and right convex hull can be recursively found
# Here Jarvis Algorithm is directly applied
left_convex_hull = ConvexHullJarvis(left).convex_hull()
right_convex_hull = ConvexHullJarvis(right).convex_hull()
# Find tangents by using tangent polygon calculator
left_polygon = Polygon(left_convex_hull)
right_polygon = Polygon(right_convex_hull)
tangent_finder = TangentPolygonCalculator()
tangent_finder[1] = left_polygon
tangent_finder[2] = right_polygon
left_upper_idx, right_upper_idx = tangent_finder.upper_tangent(
1, 2, idx=True)
left_lower_idx, right_lower_idx = tangent_finder.lower_tangent(
1, 2, idx=True)
# Need to do a collinear check else the convex hull will have extra collinear points
left_upper_idx, right_upper_idx, left_lower_idx, right_lower_idx = self.collinear_check(
left_polygon, right_polygon, left_upper_idx, right_upper_idx,
left_lower_idx, right_lower_idx)
# Merge
res = []
left_idx = left_upper_idx
# Turn counterclockwise to include the left outer convex hull points until the lower index is reached
while left_idx != left_lower_idx:
res.append(left_polygon.point_list[left_idx])
left_idx = (left_idx + 1) % len(left_polygon)
res.append(left_polygon.point_list[left_idx])
right_idx = right_upper_idx
# Turn clockwise to include the right outer convex hull points until the lower index is reached
while right_idx != right_lower_idx:
res.append(right_polygon.point_list[right_idx])
right_idx = (len(right_polygon) + right_idx -
1) % len(right_polygon)
res.append(right_polygon.point_list[right_idx])
# Use polygon to sort
sort_poly = Polygon(res)
sort_poly.sort()
return sort_poly.point_list