def construct_begin_edge(output: [Edge], tree: Tree, vertices: [Point],
ray: Ray):
vertex = ray.end
leftmost = tree.leftmost
z = ray.intersect(leftmost.edge)
if z is None:
raise ValueError("No intersections")
# finding right point for construct edge with point z
x, y = leftmost.edge.get_points()
n = x if get_angle(ray.start, ray.end, x) < get_angle(
ray.start, ray.end, y) else y
partial_edge = Edge(n, z, visible=leftmost.edge.visible)
new_node = Node(partial_edge)
edge1, edge2 = n.edges
if edge1 == leftmost.edge:
edge1 = partial_edge
else:
edge2 = partial_edge
n.edges = edge1, edge2
tree.update(old=leftmost, new=new_node, ray=ray)
new_edge = Edge(z, vertex, visible=False)
output.append(new_edge)
def update(tree: Tree, old: Edge, new: Edge, ray: Ray):
assert_edge(ray, old)
assert_edge(ray, new)
old = Node(old, ray.intersect_dist(old))
new = Node(new, ray.intersect_dist(new))
tree.update(old, new, ray)
