// Sort the vertices in anticlockwise order when looking towards the origin.
private static List <Vertex> SortVertices(IEnumerable <Vertex> vertices)
{
var vertexList = vertices.ToList();
var center = vertexList.Aggregate(Vector.Zeros(3), (c, v) => c + v.Position).Normalize();
var view = -center;
var comparer = new AnticlockwiseComparer(vertexList.First().Position, view);
var sortedVertices = vertexList.OrderBy(vertex => vertex.Position, comparer).ToList();
return(sortedVertices);
}
//TODO: Does this actually need to be given the list of vertices? Can't that be inferred from the edges?
/// <summary>
/// Build a lookup from the given vertices to the edges that contain them.
/// </summary>
/// <param name="vertices"></param>
/// <param name="edges"></param>
/// <returns></returns>
public static Dictionary <Vertex, List <Edge> > VertexToEdgeDictionary(List <Vertex> vertices, List <Edge> edges)
{
var vertexToEdges = vertices.ToDictionary(vertex => vertex, vertex => new List <Edge>());
foreach (var edge in edges)
{
vertexToEdges[edge.A].Add(edge);
vertexToEdges[edge.B].Add(edge);
}
foreach (var vertex in vertices)
{
var comparer = new AnticlockwiseComparer(vertex.Position, -vertex.Position);
var sortedEdges = vertexToEdges[vertex].OrderBy(edge => edge.SphericalCenter(), comparer);
vertexToEdges[vertex] = sortedEdges.ToList();
}
return(vertexToEdges);
}
public void Compare_ForClockwiseVectorsAroundAPoint_ShouldReturn1
(double azimuth0, double azimuth1)
{
// Fixture setup
var center = VectorUtilities.NewVector(1, 0, 0);
var view = VectorUtilities.NewVector(0, 0, -1);
var comparer = new AnticlockwiseComparer(center, view);
var lesserAzimuth = azimuth0 % (2 * Math.PI);
var greaterAzimuth = azimuth1 % (2 * Math.PI - lesserAzimuth) + lesserAzimuth;
var lessAnticlockwise = VectorUtilities.NewVector(Math.PI / 2, lesserAzimuth);
var moreAnticlockwise = VectorUtilities.NewVector(Math.PI / 2, greaterAzimuth);
var expected = 1;
// Exercise system
var actual = comparer.Compare(moreAnticlockwise, lessAnticlockwise);
// Verify outcome
TestUtilities.WriteExpectedAndActual(expected, actual);
Assert.Equal(expected, actual);
// Teardown
}
