/// <summary>
/// Returns the center of the circumcircle defined by three points (c0,
/// c1 and c2) on its edge.
/// </summary>
public static Vector2 CircumcircleCenter(Vector2 c0, Vector2 c1, Vector2 c2)
{
var mp0 = 0.5f * (c0 + c1);
var mp1 = 0.5f * (c1 + c2);
var v0 = RotateRightAngle(c0 - c1);
var v1 = RotateRightAngle(c1 - c2);
float m0, m1;
Geom.LineLineIntersection(mp0, v0, mp1, v1, out m0, out m1);
return(mp0 + m0 * v0);
}
/// <summary>
/// Clip site of voronoi diagram using polygon (must be convex),
/// returning the clipped vertices in clipped list. Modifies neither
/// polygon nor diagram, so can be run in parallel for several sites at
/// once.
/// </summary>
public void ClipSite(VoronoiDiagram diag, IList <Vector2> polygon, int site, ref List <Vector2> clipped)
{
pointsIn.Clear();
pointsIn.AddRange(polygon);
int firstEdge, lastEdge;
if (site == diag.Sites.Count - 1)
{
firstEdge = diag.FirstEdgeBySite[site];
lastEdge = diag.Edges.Count - 1;
}
else
{
firstEdge = diag.FirstEdgeBySite[site];
lastEdge = diag.FirstEdgeBySite[site + 1] - 1;
}
for (int ei = firstEdge; ei <= lastEdge; ei++)
{
pointsOut.Clear();
var edge = diag.Edges[ei];
Vector2 lp, ld;
if (edge.Type == VoronoiDiagram.EdgeType.RayCCW || edge.Type == VoronoiDiagram.EdgeType.RayCW)
{
lp = diag.Vertices[edge.Vert0];
ld = edge.Direction;
if (edge.Type == VoronoiDiagram.EdgeType.RayCW)
{
ld *= -1;
}
}
else if (edge.Type == VoronoiDiagram.EdgeType.Segment)
{
var lp0 = diag.Vertices[edge.Vert0];
var lp1 = diag.Vertices[edge.Vert1];
lp = lp0;
ld = lp1 - lp0;
}
else if (edge.Type == VoronoiDiagram.EdgeType.Line)
{
throw new NotSupportedException("Haven't implemented voronoi halfplanes yet");
}
else
{
Debug.Assert(false);
return;
}
for (int pi0 = 0; pi0 < pointsIn.Count; pi0++)
{
var pi1 = pi0 == pointsIn.Count - 1 ? 0 : pi0 + 1;
var p0 = pointsIn[pi0];
var p1 = pointsIn[pi1];
var p0Inside = Geom.ToTheLeft(p0, lp, lp + ld);
var p1Inside = Geom.ToTheLeft(p1, lp, lp + ld);
if (p0Inside && p1Inside)
{
pointsOut.Add(p1);
}
else if (!p0Inside && !p1Inside)
{
// Do nothing, both are outside
}
else
{
var intersection = Geom.LineLineIntersection(lp, ld.normalized, p0, (p1 - p0).normalized);
if (p0Inside)
{
pointsOut.Add(intersection);
}
else if (p1Inside)
{
pointsOut.Add(intersection);
pointsOut.Add(p1);
}
else
{
Debug.Assert(false);
}
}
}
var tmp = pointsIn;
pointsIn = pointsOut;
pointsOut = tmp;
}
if (clipped == null)
{
clipped = new List <Vector2>();
}
else
{
clipped.Clear();
}
clipped.AddRange(pointsIn);
}