/// <summary>
/// Merges a point to a convex hull that is a line segment.
/// </summary>
/// <param name="point">The point.</param>
private void GrowLinearConvex(Vector3F point)
{
Debug.Assert(_mesh != null);
Debug.Assert(_mesh.Vertices.Count == 2, "DCEL mesh with 2 vertices was expected.");
Debug.Assert(_type == ConvexHullType.Linear);
Debug.Assert(!Vector3F.AreNumericallyEqual(_mesh.Vertex.Position, point));
Debug.Assert(!Vector3F.AreNumericallyEqual(_mesh.Vertices[1].Position, point));
// Abort if the point is equal to an existing point.
if (Vector3F.AreNumericallyEqual(point, _mesh.Vertex.Position)
|| Vector3F.AreNumericallyEqual(point, _mesh.Vertex.Edge.Twin.Origin.Position))
return;
var edge = _mesh.Vertex.Edge;
var collinearity = DcelMesh.GetCollinearity(point, _mesh.Vertex.Edge);
switch (collinearity)
{
case Collinearity.CollinearBefore: // The point is the new start of the line segment.
edge.Origin.Position = point;
_mesh.Dirty = true;
return;
case Collinearity.CollinearAfter: // The point is the new end of the line segment.
edge.Twin.Origin.Position = point;
_mesh.Dirty = true;
return;
case Collinearity.CollinearContained: // The point is in the line segment.
// Point is in convex hull.
return;
}
Debug.Assert(collinearity == Collinearity.NotCollinear
|| collinearity == Collinearity.NotCollinearBehind
|| collinearity == Collinearity.NotCollinearInFront);
// Not Collinear --> Make triangle.
_type = ConvexHullType.Planar;
// Create new components.
DcelVertex v0 = _mesh.Vertex;
DcelVertex v1 = edge.Twin.Origin;
DcelVertex v2 = new DcelVertex(point, null);
DcelEdge e01 = edge;
DcelEdge e10 = e01.Twin;
DcelEdge e12 = new DcelEdge();
DcelEdge e21 = new DcelEdge();
DcelEdge e02 = new DcelEdge();
DcelEdge e20 = new DcelEdge();
DcelFace f012 = new DcelFace();
DcelFace f210 = new DcelFace();
// Link with existing components.
e01.Next = e12; e01.Previous = e20;
e10.Next = e02; e10.Previous = e21;
// Link new components.
v2.Edge = e20;
e12.Origin = v1;
e21.Origin = v2;
e20.Origin = v2;
e02.Origin = v0;
e12.Twin = e21;
e21.Twin = e12;
e20.Twin = e02;
e02.Twin = e20;
e12.Previous = e01;
e21.Previous = e02;
e20.Previous = e12;
e02.Previous = e10;
e12.Next = e20;
e21.Next = e10;
e20.Next = e01;
e02.Next = e21;
// Link face.
f012.Boundary = e01;
f210.Boundary = e21;
e01.Face = e12.Face = e20.Face = f012;
e21.Face = e10.Face = e02.Face = f210;
// Update _faces.
_faces.Add(f012);
_faces.Add(f210);
_mesh.Dirty = true;
Debug.Assert(_mesh.Faces.Count == _faces.Count, "Internal error in ConvexHullBuilder.");
Debug.Assert(_mesh.IsTriangleMesh(), "DCEL mesh should be a triangle mesh.");
Debug.Assert(_mesh.IsTwoSidedPolygon(), "DCEL mesh should be a two-sided polygon.");
}
/// <summary>
/// Merges a point to an empty convex hull.
/// </summary>
/// <param name="point">The point.</param>
private void GrowEmptyConvex(Vector3F point)
{
Debug.Assert(_mesh != null);
Debug.Assert(_mesh.Vertices.Count == 0, "DCEL mesh is not empty.");
Debug.Assert(_type == ConvexHullType.Empty);
// Create a single vertex.
_mesh.Vertex = new DcelVertex(point, null);
_mesh.Dirty = true;
_type = ConvexHullType.Point;
}
/// <summary>
/// Merges a point to a convex hull that is also a point.
/// </summary>
/// <param name="point">The point.</param>
private void GrowPointConvex(Vector3F point)
{
Debug.Assert(_mesh != null);
Debug.Assert(_mesh.Vertices.Count == 1, "DCEL mesh with 1 vertex was expected.");
Debug.Assert(_type == ConvexHullType.Point);
// Abort if the point is equal to the existing point in the mesh.
if (Vector3F.AreNumericallyEqual(_mesh.Vertex.Position, point))
return;
DcelVertex newVertex = new DcelVertex(point, null);
DcelEdge edge = new DcelEdge();
DcelEdge twin = new DcelEdge();
// Link everything.
edge.Origin = _mesh.Vertex;
twin.Origin = newVertex;
edge.Twin = twin;
twin.Twin = edge;
_mesh.Vertex.Edge = edge;
newVertex.Edge = twin;
_mesh.Dirty = true;
_type = ConvexHullType.Linear;
}
public void Reset()
{
// Reset fields.
_faces = new List<DcelFace>();
_taggedEdges = new List<DcelEdge>();
_isPlanar = false;
_type = ConvexHullType.Empty;
_mesh = new DcelMesh();
}
/// <summary>
/// Removes the given face and connects the face edges to the given point.
/// </summary>
/// <param name="face">The face.</param>
/// <param name="point">The point.</param>
private void GrowPlanarConvexToSpatial(DcelFace face, Vector3F point)
{
_faces.Remove(face);
// Create a new vertex for the point.
DcelVertex newVertex = new DcelVertex(point, null);
// Traverse the boundary of the face.
DcelEdge currentEdge = face.Boundary;
DcelEdge previousEdge = null;
do
{
// Create new face.
DcelFace newface = new DcelFace();
newface.Boundary = currentEdge;
currentEdge.Face = newface;
_faces.Add(newface);
// Create 2 half-edges.
currentEdge.Next = new DcelEdge();
currentEdge.Previous = new DcelEdge();
currentEdge.Next.Face = newface;
currentEdge.Next.Origin = currentEdge.Twin.Origin;
currentEdge.Next.Previous = currentEdge;
currentEdge.Next.Next = currentEdge.Previous;
currentEdge.Previous.Face = newface;
currentEdge.Previous.Origin = newVertex;
currentEdge.Previous.Previous = currentEdge.Next;
currentEdge.Previous.Next = currentEdge;
// Link new face with previous new face.
if (previousEdge != null)
{
previousEdge.Next.Twin = currentEdge.Previous;
currentEdge.Previous.Twin = previousEdge.Next;
}
// Go to next edge.
previousEdge = currentEdge;
currentEdge = currentEdge.Twin.Previous.Twin;
// Go on until no edge points to face anymore.
} while (currentEdge.Face == face);
// Link the last new face with the first new face.
previousEdge.Next.Twin = currentEdge.Previous;
currentEdge.Previous.Twin = previousEdge.Next;
Debug.Assert(previousEdge != null);
Debug.Assert(currentEdge == face.Boundary);
Debug.Assert(currentEdge.Face != face);
// Set the data for the new vertex.
newVertex.Edge = currentEdge.Previous;
_mesh.Dirty = true;
_type = ConvexHullType.Spatial;
Debug.Assert(_mesh.Faces.Count == _faces.Count, "Internal error in ConvexHullBuilder.");
}