/// <summary>
/// Thickens each mesh edge in the plane of the mesh surface.
/// </summary>
/// <param name="offset">Distance to offset edges in plane of adjacent faces</param>
/// <param name="boundaries">If true, attempt to ribbon boundary edges</param>
/// <returns>The ribbon mesh</returns>
public Mesh Ribbon(float offset, Boolean boundaries, float smooth)
{
Mesh ribbon = Duplicate();
var orig_faces = ribbon.Faces.ToArray();
List <List <Halfedge> > incidentEdges = ribbon.Vertices.Select(v => v.Halfedges).ToList();
// create new "vertex" faces
List <List <Vertex> > all_new_vertices = new List <List <Vertex> >();
for (int k = 0; k < Vertices.Count; k++)
{
Vertex v = ribbon.Vertices[k];
List <Vertex> new_vertices = new List <Vertex>();
List <Halfedge> halfedges = incidentEdges[k];
Boolean boundary = halfedges[0].Next.Pair != halfedges[halfedges.Count - 1];
// if the edge loop around this vertex is open, close it with 'temporary edges'
if (boundaries && boundary)
{
Halfedge a, b;
a = halfedges[0].Next;
b = halfedges[halfedges.Count - 1];
if (a.Pair == null)
{
a.Pair = new Halfedge(a.Prev.Vertex)
{
Pair = a
};
}
if (b.Pair == null)
{
b.Pair = new Halfedge(b.Prev.Vertex)
{
Pair = b
};
}
a.Pair.Next = b.Pair;
b.Pair.Prev = a.Pair;
a.Pair.Prev = a.Pair.Prev ?? a; // temporary - to allow access to a.Pair's start/end vertices
halfedges.Add(a.Pair);
}
foreach (Halfedge edge in halfedges)
{
if (halfedges.Count < 2)
{
continue;
}
Vector3f normal = edge.Face != null ? edge.Face.Normal : Vertices[k].Normal;
Halfedge edge2 = edge.Next;
Vector3f o1 = Vector3f.CrossProduct(normal, edge.Vector);
Vector3f o2 = Vector3f.CrossProduct(normal, edge2.Vector);
o1.Unitize();
o2.Unitize();
o1 *= offset;
o2 *= offset;
if (edge.Face == null)
{
// boundary condition: create two new vertices in the plane defined by the vertex normal
Vertex v1 = new Vertex(v.Position + (edge.Vector * (1 / edge.Vector.Length) * -offset) + o1);
Vertex v2 = new Vertex(v.Position + (edge2.Vector * (1 / edge2.Vector.Length) * offset) + o2);
ribbon.Vertices.Add(v2);
ribbon.Vertices.Add(v1);
new_vertices.Add(v2);
new_vertices.Add(v1);
Halfedge c = new Halfedge(v2, edge2, edge, null);
edge.Next = c;
edge2.Prev = c;
}
else
{
// internal condition: offset each edge in the plane of the shared face and create a new vertex where they intersect eachother
Line l1 = new Line(edge.Vertex.Position + o1, edge.Prev.Vertex.Position + o1);
Line l2 = new Line(edge2.Vertex.Position + o2, edge2.Prev.Vertex.Position + o2);
double a, b;
Rhino.Geometry.Intersect.Intersection.LineLine(l1, l2, out a, out b);
Point3d new_point = l1.PointAt(a);
Vertex new_vertex = new Vertex(new Point3f((float)new_point.X, (float)new_point.Y, (float)new_point.Z));
ribbon.Vertices.Add(new_vertex);
new_vertices.Add(new_vertex);
}
}
if ((!boundaries && boundary) == false) // only draw boundary node-faces in 'boundaries' mode
{
ribbon.Faces.Add(new_vertices);
}
all_new_vertices.Add(new_vertices);
}
// change edges to reference new vertices
for (int k = 0; k < Vertices.Count; k++)
{
Vertex v = ribbon.Vertices[k];
if (all_new_vertices[k].Count < 1)
{
continue;
}
int c = 0;
foreach (Halfedge edge in incidentEdges[k])
{
if (!ribbon.Halfedges.SetVertex(edge, all_new_vertices[k][c++]))
{
edge.Vertex = all_new_vertices[k][c];
}
}
//v.Halfedge = null; // unlink from halfedge as no longer in use (culled later)
// note: new vertices don't link to any halfedges in the mesh until later
}
// cull old vertices
ribbon.Vertices.RemoveRange(0, Vertices.Count);
// use existing edges to create 'ribbon' faces
MeshHalfedgeList temp = new MeshHalfedgeList();
for (int i = 0; i < Halfedges.Count; i++)
{
temp.Add(ribbon.Halfedges[i]);
}
List <Halfedge> items = temp.GetUnique();
foreach (Halfedge halfedge in items)
{
if (halfedge.Pair != null)
{
// insert extra vertices close to the new 'vertex' vertices to preserve shape when subdividing
if (smooth > 0.0)
{
if (smooth > 0.5)
{
smooth = 0.5f;
}
Vertex[] new_vertices = new Vertex[] {
new Vertex(halfedge.Vertex.Position + (-smooth * halfedge.Vector)),
new Vertex(halfedge.Prev.Vertex.Position + (smooth * halfedge.Vector)),
new Vertex(halfedge.Pair.Vertex.Position + (-smooth * halfedge.Pair.Vector)),
new Vertex(halfedge.Pair.Prev.Vertex.Position + (smooth * halfedge.Pair.Vector))
};
ribbon.Vertices.AddRange(new_vertices);
Vertex[] new_vertices1 = new Vertex[] {
halfedge.Vertex,
new_vertices[0],
new_vertices[3],
halfedge.Pair.Prev.Vertex
};
Vertex[] new_vertices2 = new Vertex[] {
new_vertices[1],
halfedge.Prev.Vertex,
halfedge.Pair.Vertex,
new_vertices[2]
};
ribbon.Faces.Add(new_vertices);
ribbon.Faces.Add(new_vertices1);
ribbon.Faces.Add(new_vertices2);
}
else
{
Vertex[] new_vertices = new Vertex[] {
halfedge.Vertex,
halfedge.Prev.Vertex,
halfedge.Pair.Vertex,
halfedge.Pair.Prev.Vertex
};
ribbon.Faces.Add(new_vertices);
}
}
}
// remove original faces, leaving just the ribbon
//var orig_faces = Enumerable.Range(0, Faces.Count).Select(i => ribbon.Faces[i]);
foreach (Face item in orig_faces)
{
ribbon.Faces.Remove(item);
}
// search and link pairs
ribbon.Halfedges.MatchPairs();
return(ribbon);
}
public Mesh()
{
Halfedges = new MeshHalfedgeList(this);
Vertices = new MeshVertexList(this);
Faces = new MeshFaceList(this);
}
