/// <summary>
/// Given an edge AB, it searches for the triangle that has an edge with the same vertices in the same order.
/// </summary>
/// <remarks>
/// Remember that the vertices of a triangle are sorted counter-clockwise.
/// </remarks>
/// <param name="edgeVertexA">The index of the first vertex of the edge.</param>
/// <param name="edgeVertexB">The index of the second vertex of the edge.</param>
/// <returns>The data of the triangle.</returns>
public DelaunayTriangleEdge FindTriangleThatContainsEdge(int edgeVertexA, int edgeVertexB)
{
DelaunayTriangleEdge foundTriangle = new DelaunayTriangleEdge(NOT_FOUND, NOT_FOUND, edgeVertexA, edgeVertexB);
for (int i = 0; i < TriangleCount; ++i)
{
for (int j = 0; j < 3; ++j)
{
if (m_triangleVertices[i * 3 + j] == edgeVertexA && m_triangleVertices[i * 3 + (j + 1) % 3] == edgeVertexB)
{
foundTriangle.TriangleIndex = i;
foundTriangle.EdgeIndex = j;
break;
}
}
}
return(foundTriangle);
}
/// <summary>
/// Adds an edge to the triangulation in such a way that it keeps there even if it form triangles that do not fulfill the Delaunay constraint.
/// If the edge already exists, nothing will be done.
/// </summary>
/// <remarks>
/// The order in which the vertices of the edges are provided is important, as the edge may be part of a polygon whose vertices are sorted CCW.
/// </remarks>
/// <param name="endpointAIndex">The index of the first vertex of the edge, in the existing triangulation.</param>
/// <param name="endpointBIndex">The index of the second vertex of the edge, in the existing triangulation.</param>
private void AddConstrainedEdgeToTriangulation(int endpointAIndex, int endpointBIndex)
{
// Detects if the edge already exists
if (m_triangleSet.FindTriangleThatContainsEdge(endpointAIndex, endpointBIndex).TriangleIndex != NOT_FOUND)
{
return;
}
Vector2 edgeEndpointA = m_triangleSet.GetPointByIndex(endpointAIndex);
Vector2 edgeEndpointB = m_triangleSet.GetPointByIndex(endpointBIndex);
// 5.3.1: Search for the triangle that contains the beginning of the new edge
int triangleContainingA = m_triangleSet.FindTriangleThatContainsLineEndpoint(endpointAIndex, endpointBIndex);
// 5.3.2: Get all the triangle edges intersected by the constrained edge
List <DelaunayTriangleEdge> intersectedTriangleEdges = new List <DelaunayTriangleEdge>();
m_triangleSet.GetIntersectingEdges(edgeEndpointA, edgeEndpointB, triangleContainingA, intersectedTriangleEdges);
List <DelaunayTriangleEdge> newEdges = new List <DelaunayTriangleEdge>();
while (intersectedTriangleEdges.Count > 0)
{
DelaunayTriangleEdge currentIntersectedTriangleEdge = intersectedTriangleEdges[intersectedTriangleEdges.Count - 1];
intersectedTriangleEdges.RemoveAt(intersectedTriangleEdges.Count - 1);
// 5.3.3: Form quadrilaterals and swap intersected edges
// Deduces the data for both triangles
currentIntersectedTriangleEdge = m_triangleSet.FindTriangleThatContainsEdge(currentIntersectedTriangleEdge.EdgeVertexA, currentIntersectedTriangleEdge.EdgeVertexB);
DelaunayTriangle intersectedTriangle = m_triangleSet.GetTriangle(currentIntersectedTriangleEdge.TriangleIndex);
DelaunayTriangle oppositeTriangle = m_triangleSet.GetTriangle(intersectedTriangle.adjacent[currentIntersectedTriangleEdge.EdgeIndex]);
Triangle2D trianglePoints = m_triangleSet.GetTrianglePoints(currentIntersectedTriangleEdge.TriangleIndex);
// Gets the opposite vertex of adjacent triangle, knowing the fisrt vertex of the shared edge
int oppositeVertex = NOT_FOUND;
//List<int> debugP = intersectedTriangle.DebugP;
//List<int> debugA = intersectedTriangle.DebugAdjacent;
//List<int> debugP2 = oppositeTriangle.DebugP;
//List<int> debugA2 = oppositeTriangle.DebugAdjacent;
int oppositeSharedEdgeVertex = NOT_FOUND; // The first vertex in the shared edge of the opposite triangle
for (int j = 0; j < 3; ++j)
{
if (oppositeTriangle.p[j] == intersectedTriangle.p[(currentIntersectedTriangleEdge.EdgeIndex + 1) % 3]) // Comparing with the endpoint B of the edge, since the edge AB is BA in the adjacent triangle
{
oppositeVertex = oppositeTriangle.p[(j + 2) % 3];
oppositeSharedEdgeVertex = j;
break;
}
}
Vector2 oppositePoint = m_triangleSet.GetPointByIndex(oppositeVertex);
if (MathUtils.IsQuadrilateralConvex(trianglePoints.p0, trianglePoints.p1, trianglePoints.p2, oppositePoint))
{
// Swap
int notInEdgeTriangleVertex = (currentIntersectedTriangleEdge.EdgeIndex + 2) % 3;
SwapEdges(currentIntersectedTriangleEdge.TriangleIndex, intersectedTriangle, notInEdgeTriangleVertex, oppositeTriangle, oppositeSharedEdgeVertex);
// Refreshes triangle data after swapping
intersectedTriangle = m_triangleSet.GetTriangle(currentIntersectedTriangleEdge.TriangleIndex);
//oppositeTriangle = m_triangles.GetTriangle(intersectedTriangle.adjacent[(currentIntersectedTriangleEdge.EdgeIndex + 2) % 3]);
//debugP = intersectedTriangle.DebugP;
//debugA = intersectedTriangle.DebugAdjacent;
//debugP2 = oppositeTriangle.DebugP;
//debugA2 = oppositeTriangle.DebugAdjacent;
// Check new diagonal against the intersecting edge
Vector2 intersectionPoint;
int newTriangleSharedEdgeVertex = (currentIntersectedTriangleEdge.EdgeIndex + 2) % 3; // Read SwapEdges method to understand the +2
Vector2 newTriangleSharedEdgePointA = m_triangleSet.GetPointByIndex(intersectedTriangle.p[newTriangleSharedEdgeVertex]);
Vector2 newTriangleSharedEdgePointB = m_triangleSet.GetPointByIndex(intersectedTriangle.p[(newTriangleSharedEdgeVertex + 1) % 3]);
DelaunayTriangleEdge newEdge = new DelaunayTriangleEdge(NOT_FOUND, NOT_FOUND, intersectedTriangle.p[newTriangleSharedEdgeVertex], intersectedTriangle.p[(newTriangleSharedEdgeVertex + 1) % 3]);
if (newTriangleSharedEdgePointA != edgeEndpointB && newTriangleSharedEdgePointB != edgeEndpointB && // Watch out! It thinks the line intersects with the edge when an endpoint coincides with a triangle vertex, this problem is avoided thanks to this conditions
newTriangleSharedEdgePointA != edgeEndpointA && newTriangleSharedEdgePointB != edgeEndpointA &&
MathUtils.IntersectionBetweenLines(edgeEndpointA, edgeEndpointB, newTriangleSharedEdgePointA, newTriangleSharedEdgePointB, out intersectionPoint))
{
// New triangles edge still intersects with the constrained edge, so it is returned to the list
intersectedTriangleEdges.Insert(0, newEdge);
}
else
{
newEdges.Add(newEdge);
}
}
else
{
// Back to the list
intersectedTriangleEdges.Insert(0, currentIntersectedTriangleEdge);
}
}
// 5.3.4. Check Delaunay constraint and swap edges
for (int i = 0; i < newEdges.Count; ++i)
{
// Checks if the constrained edge coincides with the new edge
Vector2 triangleEdgePointA = m_triangleSet.GetPointByIndex(newEdges[i].EdgeVertexA);
Vector2 triangleEdgePointB = m_triangleSet.GetPointByIndex(newEdges[i].EdgeVertexB);
if ((triangleEdgePointA == edgeEndpointA && triangleEdgePointB == edgeEndpointB) ||
(triangleEdgePointB == edgeEndpointA && triangleEdgePointA == edgeEndpointB))
{
continue;
}
// Deduces the data for both triangles
DelaunayTriangleEdge currentEdge = m_triangleSet.FindTriangleThatContainsEdge(newEdges[i].EdgeVertexA, newEdges[i].EdgeVertexB);
DelaunayTriangle currentEdgeTriangle = m_triangleSet.GetTriangle(currentEdge.TriangleIndex);
int triangleVertexNotShared = (currentEdge.EdgeIndex + 2) % 3;
Vector2 trianglePointNotShared = m_triangleSet.GetPointByIndex(currentEdgeTriangle.p[triangleVertexNotShared]);
DelaunayTriangle oppositeTriangle = m_triangleSet.GetTriangle(currentEdgeTriangle.adjacent[currentEdge.EdgeIndex]);
Triangle2D oppositeTrianglePoints = m_triangleSet.GetTrianglePoints(currentEdgeTriangle.adjacent[currentEdge.EdgeIndex]);
//List<int> debugP = currentEdgeTriangle.DebugP;
//List<int> debugA = currentEdgeTriangle.DebugAdjacent;
//List<int> debugP2 = oppositeTriangle.DebugP;
//List<int> debugA2 = oppositeTriangle.DebugAdjacent;
if (MathUtils.IsPointInsideCircumcircle(oppositeTrianglePoints.p0, oppositeTrianglePoints.p1, oppositeTrianglePoints.p2, trianglePointNotShared))
{
// Finds the edge of the opposite triangle that is shared with the other triangle, this edge will be swapped
int sharedEdgeVertexLocalIndex = 0;
for (; sharedEdgeVertexLocalIndex < 3; ++sharedEdgeVertexLocalIndex)
{
if (oppositeTriangle.adjacent[sharedEdgeVertexLocalIndex] == currentEdge.TriangleIndex)
{
break;
}
}
// Swap
SwapEdges(currentEdge.TriangleIndex, currentEdgeTriangle, triangleVertexNotShared, oppositeTriangle, sharedEdgeVertexLocalIndex);
}
}
//Debug.DrawLine(edgeEndpointA, edgeEndpointB, Color.magenta, 10.0f);
}
/// <summary>
/// Given the outline of a closed polygon, expressed as a list of vertices, it finds all the triangles that lay inside of the figure.
/// </summary>
/// <param name="polygonOutline">The outline, a list of vertex indices sorted counter-clockwise.</param>
/// <param name="outputTrianglesInPolygon">The list where the triangles found inside the polygon will be added. No elements are removed from this list.</param>
public void GetTrianglesInPolygon(List <int> polygonOutline, List <int> outputTrianglesInPolygon)
{
// This method assumes that the edges of the triangles to find were created using the same vertex order
// It also assumes all triangles are inside a supertriangle, so no adjacent triangles are -1
Stack <int> adjacentTriangles = new Stack <int>();
// First it gets all the triangles of the outline
for (int i = 0; i < polygonOutline.Count; ++i)
{
// For every edge, it gets the inner triangle that contains such edge
DelaunayTriangleEdge triangleEdge = FindTriangleThatContainsEdge(polygonOutline[i], polygonOutline[(i + 1) % polygonOutline.Count]);
// A triangle may form a corner, with 2 consecutive outline edges. This avoids adding it twice
if (outputTrianglesInPolygon.Count > 0 &&
(outputTrianglesInPolygon[outputTrianglesInPolygon.Count - 1] == triangleEdge.TriangleIndex || // Is the last added triangle the same as current?
outputTrianglesInPolygon[0] == triangleEdge.TriangleIndex)) // Is the first added triangle the same as the current, which is the last to be added (closes the polygon)?
{
continue;
}
outputTrianglesInPolygon.Add(triangleEdge.TriangleIndex);
int previousOutlineEdgeVertexA = polygonOutline[(i + polygonOutline.Count - 1) % polygonOutline.Count];
int previousOutlineEdgeVertexB = polygonOutline[i];
int nextOutlineEdgeVertexA = polygonOutline[(i + 1) % polygonOutline.Count];
int nextOutlineEdgeVertexB = polygonOutline[(i + 2) % polygonOutline.Count];
for (int j = 1; j < 3; ++j) // For the 2 adjacent triangles of the other 2 edges
{
int adjacentTriangle = m_adjacentTriangles[triangleEdge.TriangleIndex * 3 + (triangleEdge.EdgeIndex + j) % 3];
bool isAdjacentTriangleInOutline = false;
// Compares the contiguous edges of the outline, to the right and to the left of the current one, flipped and not flipped, with the adjacent triangle's edges
for (int k = 0; k < 3; ++k)
{
int currentTriangleEdgeVertexA = m_triangleVertices[adjacentTriangle * 3 + k];
int currentTriangleEdgeVertexB = m_triangleVertices[adjacentTriangle * 3 + (k + 1) % 3];
if ((currentTriangleEdgeVertexA == previousOutlineEdgeVertexA && currentTriangleEdgeVertexB == previousOutlineEdgeVertexB) ||
(currentTriangleEdgeVertexA == previousOutlineEdgeVertexB && currentTriangleEdgeVertexB == previousOutlineEdgeVertexA) ||
(currentTriangleEdgeVertexA == nextOutlineEdgeVertexA && currentTriangleEdgeVertexB == nextOutlineEdgeVertexB) ||
(currentTriangleEdgeVertexA == nextOutlineEdgeVertexB && currentTriangleEdgeVertexB == nextOutlineEdgeVertexA))
{
isAdjacentTriangleInOutline = true;
}
}
if (!isAdjacentTriangleInOutline && !outputTrianglesInPolygon.Contains(adjacentTriangle))
{
adjacentTriangles.Push(adjacentTriangle);
}
}
}
// Then it propagates by adjacency, stopping when an adjacent triangle has already been included in the list
// Since all the outline triangles have been added previously, it will not propagate outside of the polygon
while (adjacentTriangles.Count > 0)
{
int currentTriangle = adjacentTriangles.Pop();
// The triangle may have been added already in a previous iteration
if (outputTrianglesInPolygon.Contains(currentTriangle))
{
continue;
}
for (int i = 0; i < 3; ++i)
{
int adjacentTriangle = m_adjacentTriangles[currentTriangle * 3 + i];
if (adjacentTriangle != NO_ADJACENT_TRIANGLE && !outputTrianglesInPolygon.Contains(adjacentTriangle))
{
adjacentTriangles.Push(adjacentTriangle);
}
}
outputTrianglesInPolygon.Add(currentTriangle);
}
}