/// <summary>
/// Find the triangle(s) containing the given point. The search starts from an arbitrary
/// triangle and homes in on the vertex by visiting triangles closest to the vertex.
/// If the vertex is on and edge seperating two triangles, both are returned.
/// </summary>
/// <param name="v">The vertex to search for</param>
/// <returns>The triangles(s) containing the vertex</returns>
internal FindTriangle[] FindContaining(Vertex v)
{
Triangle current = root;
while (true)
{
PointOnTriangle loc = PointOnTriangle.None;
Halfedge closestEdge = null;
PointShapeRelation rel = current.Contains(v, out loc, out closestEdge);
if (rel == PointShapeRelation.Inside)
{
// Inside triangle, return.
return(new FindTriangle[] { new FindTriangle(current, rel, loc) });
}
else if (rel == PointShapeRelation.Outside)
{
// Outside triangle, continue searching from the neighbour closest to the point
Halfedge opp = closestEdge.Opposite;
if (opp == null)
{
throw new InvalidOperationException("No triangle contains this vertex.");
}
current = opp.Parent;
}
else
{
// On an edge, return the triangle and its neighbour (if there is one)
Halfedge opp = closestEdge.Opposite;
if (opp == null)
{
return(new FindTriangle[] { new FindTriangle(current, rel, loc) });
}
else
{
Triangle other = opp.Parent;
PointOnTriangle otherLoc = PointOnTriangle.None;
PointShapeRelation otherRel = other.Contains(v, out otherLoc);
return(new FindTriangle[] { new FindTriangle(current, rel, loc), new FindTriangle(other, otherRel, otherLoc) });
}
}
}
}
public FindTriangle(Triangle tri, PointShapeRelation rel, PointOnTriangle loc)
{
Triangle = tri;
Relation = rel;
Location = loc;
}
