circle_2 get_circumcircle(triangle_2 const &t) const
{
if (t[0] == t[1] && t[1] == t[2])
return circle_2(t[0], 0);
if (orientation(t[0], t[1], t[2]) == cg::CG_COLLINEAR)
{
auto minmax = std::minmax({t[0], t[1], t[2]});
point_2 p1 = minmax.first;
point_2 p2 = minmax.second;
if (t[0] != t[1])
p2 = t[1];
else
p2 = t[2];
point_2 center = p1 + vector_2((p2.x - p1.x) / 2, (p2.y - p1.y) / 2);
double radius = segment_2(p1, p2).length() / 2;
return circle_2(center, radius);
}
double A1 = t[1].x - t[0].x;
double B1 = t[1].y - t[0].y;
double C1 = (t[1].x - t[0].x) * (t[1].x + t[0].x) / 2 + (t[1].y - t[0].y) * (t[1].y + t[0].y) / 2;
double A2 = t[2].x - t[0].x;
double B2 = t[2].y - t[0].y;
double C2 = (t[2].x - t[0].x) * (t[2].x + t[0].x) / 2 + (t[2].y - t[0].y) * (t[2].y + t[0].y) / 2;
point_2 center((C1 * B2 - C2 * B1) / (A1 * B2 - A2 * B1),
(A1 * C2 - A2 * C1) / (A1 * B2 - A2 * B1));
double radius = segment_2(center, t[0]).length();
return circle_2(center, radius);
}
void calc_visibility_graph()
{
int n = 0;
for (contour_2 &c : contours)
{
if (!counterclockwise(c))
{
c.reverse();
std::reverse(points.begin() + n, points.begin() + n + c.size());
}
n += c.size();
}
graph g = visibility_graph(contours.begin(), contours.end(), true);
visibility_segments.clear();
for (int i = 0; i < (int) points.size(); ++i)
{
std::vector<int> const &edges = g.get_edges(i);
for (int j : edges)
visibility_segments.push_back(segment_2(points[i], points[j]));
}
}