/// <summary>
/// Get the list of triangles containing the given vertex.
/// </summary>
/// <param name="index"></param>
/// <returns></returns>
public List <Triangle> GetTrianglesContainingVertex(VertexIndex index)
{
triangles.Clear();
for (int i = 0; i < numTrianglesByIndex[index]; i++)
{
triangles.Add(triangleLookup[index, i]);
}
return(triangles);
}
bool IsOutlineEdge(VertexIndex vertexA, VertexIndex vertexB)
{
if (vertexA == vertexB)
{
return(false);
}
return(!DoVerticesShareMultipleTriangles(vertexA, vertexB));
}
void FollowOutline(VertexIndex vertexIndex, List <VertexIndex> outline)
{
outline.Add(vertexIndex);
visited[vertexIndex] = true;
VertexIndex nextVertexIndex;
if (TryGetConnectedOutlineVertex(vertexIndex, out nextVertexIndex))
{
FollowOutline(nextVertexIndex, outline);
}
}
VertexIndex GetThirdPoint(VertexIndex indexA, VertexIndex indexB, Triangle triangle)
{
foreach (int triangleIndex in triangle.vertices)
{
VertexIndex vertexIndex = triangles[triangleIndex];
if (vertexIndex != indexA && vertexIndex != indexB)
{
return(vertexIndex);
}
}
throw new ArgumentException("Unexpected error: outline generation failed.");
}
Outline GenerateOutlineFromPoint(VertexIndex startVertexIndex)
{
visited[startVertexIndex] = true;
outlineTemp.Clear();
outlineTemp.Add(startVertexIndex);
VertexIndex nextVertexIndex = GetInitialConnectedOutlineVertex(startVertexIndex);
FollowOutline(nextVertexIndex, outlineTemp);
outlineTemp.Add(startVertexIndex);
return(new Outline(outlineTemp));
}
/// <summary>
/// Generate and return the outlines based on the data passed in during instantiation.
/// </summary>
public IList <Outline> GenerateOutlines()
{
var outlines = new List <Outline>();
visited = new bool[vertices.Length];
for (VertexIndex index = 0; index < vertices.Length; index++)
{
if (!visited[index] && MustBeOutlineVertex(index))
{
outlines.Add(GenerateOutlineFromPoint(index));
}
}
return(outlines.AsReadOnly());
}
bool DoVerticesShareMultipleTriangles(VertexIndex vertexA, VertexIndex vertexB)
{
int sharedTriangleCount = 0;
List <Triangle> containingTriangles = triangleLookup.GetTrianglesContainingVertex(vertexA);
for (int i = 0; i < containingTriangles.Count; i++)
{
if (IsVertexContainedInTriangle(containingTriangles[i], vertexB))
{
sharedTriangleCount++;
if (sharedTriangleCount > 1)
{
return(true);
}
}
}
return(false);
}
VertexIndex GetInitialConnectedOutlineVertex(VertexIndex startIndex)
{
List <Triangle> containingTriangles = triangleLookup.GetTrianglesContainingVertex(startIndex);
for (int i = 0; i < containingTriangles.Count; i++)
{
Triangle triangle = containingTriangles[i];
int[] triangleIndices = ExtractTriangleIndices(triangle);
foreach (int nextIndex in triangleIndices)
{
VertexIndex vertexIndex = triangles[nextIndex];
if (IsOutlineEdge(startIndex, vertexIndex) && IsCorrectOrientation(startIndex, vertexIndex, triangle))
{
return(vertexIndex);
}
}
}
throw new InvalidOperationException("Failed to initialize outline during mesh generation.");
}
bool TryGetConnectedOutlineVertex(VertexIndex currentIndex, out VertexIndex nextIndex)
{
List <Triangle> containingTriangles = triangleLookup.GetTrianglesContainingVertex(currentIndex);
for (int i = 0; i < containingTriangles.Count; i++)
{
int[] triangleIndices = ExtractTriangleIndices(containingTriangles[i]);
foreach (int index in triangleIndices)
{
VertexIndex vertexIndex = triangles[index];
if (!visited[vertexIndex] && IsOutlineEdge(currentIndex, vertexIndex))
{
nextIndex = vertexIndex;
return(true);
}
}
}
nextIndex = new VertexIndex();
return(false);
}
public bool DoVerticesShareMultipleTriangles(VertexIndex indexA, VertexIndex indexB)
{
int a = numTrianglesByIndex[indexA];
int b = numTrianglesByIndex[indexB];
int sharedTriangleCount = 0;
for (int x = 0; x < a; x++)
{
for (int y = 0; y < b; y++)
{
if (triangleLookup[indexA, x] == triangleLookup[indexB, y])
{
sharedTriangleCount++;
if (sharedTriangleCount > 1)
{
return(true);
}
}
}
}
return(false);
}
/// <summary>
/// Sufficient (but not necessary) test for the vertex index to be on an outline. For each outline, at least one
/// vertex will have an index that returns true according to this method. As such, indices failing this test
/// can be ignored while still ensuring every outline is discovered.
/// </summary>
bool MustBeOutlineVertex(VertexIndex vertexIndex)
{
int numTrianglesContainingVertex = triangleLookup.CountTrianglesContainingVertex(vertexIndex);
return(numTrianglesContainingVertex <= MAX_CONTAINING_TRIANGLES_ENSURING_OUTLINE_INDEX);
}
/// <summary>
/// Will these indices produce an Outline going in the right direction? The direction of the Outline will determine
/// whether the walls are visible.
/// </summary>
/// <param name="startIndex">The starting index.</param>
/// <param name="otherIndex">The discovered index in question.</param>
/// <param name="triangle">A triangle containing both indices.</param>
/// <returns>Returns whether going from the start index to the discovered index will result in a correctly
/// oriented Outline.</returns>
bool IsCorrectOrientation(VertexIndex startIndex, VertexIndex otherIndex, Triangle triangle)
{
VertexIndex outsideIndex = GetThirdPoint(startIndex, otherIndex, triangle);
return(IsRightOf(vertices[startIndex], vertices[otherIndex], vertices[outsideIndex]));
}
bool IsVertexContainedInTriangle(Triangle triangle, VertexIndex vertex)
{
return(triangles[triangle.a] == vertex || triangles[triangle.b] == vertex || triangles[triangle.c] == vertex);
}
bool IsOutlineEdge(VertexIndex vertexA, VertexIndex vertexB)
{
return(vertexA != vertexB && !triangleLookup.DoVerticesShareMultipleTriangles(vertexA, vertexB));
}
/// <summary>
/// How many triangles contain the given vertex?
/// </summary>
/// <param name="index"></param>
/// <returns></returns>
public int CountTrianglesContainingVertex(VertexIndex index)
{
return(numTrianglesByIndex[index]);
}
void AddTriangle(VertexIndex a, VertexIndex b, VertexIndex c)
{
triangles.Add(a);
triangles.Add(b);
triangles.Add(c);
}