public static int Pop(this IntSet self)
{
if (self.Count == 0)
{
throw new InvalidOperationException();
}
int result = self.First();
self.Remove(result);
return(result);
}
/// <summary>
/// Clips the mesh with the given plane.
/// The part on the positive hals will remain.
/// Will return null when everything is clipped.
/// Cap-faces will be built on everything that is cut open by the plane (non-convex cap faces are not handled properly).
/// Only works for meshes without Face-/FaceVertexAttributes -> attributes will be invalid for generated faces.
/// </summary>
public PolyMesh ClipByPlane(Plane3d plane, double epsilon = 1e-7)
{
var clippedMesh = SplitOnPlane(plane, epsilon).Item2;
// in case everything is clipped away
if (clippedMesh == null)
{
return(null);
}
// 1. go trough all edges
// 2. if edge on plane -> test if there is an open face along the plane (border edges)
var vertexOnPlane = clippedMesh.PositionArray.Map(clippedMesh.VertexCount, p => plane.Height(p).Abs() <= epsilon);
clippedMesh.BuildTopology();
// use indices so an edge can be removed no matter what "ref"
var edges = new IntSet(clippedMesh.EdgeCount);
foreach (var e in clippedMesh.Edges)
{
if (e.IsValid)
{
edges.Add(e.Index);
}
}
var capFaceEdges = new List <PolyMesh.Edge>();
var capFaceEdgeSet = new IntSet();
while (edges.Count > 0)
{
var e = clippedMesh.GetEdge(edges.First());
edges.Remove(e.Index);
if (e.IsAnyBorder &&
vertexOnPlane[e.FromVertexIndex] &&
vertexOnPlane[e.ToVertexIndex])
{
// try to find other edges along the plane
// keep set of all edges so in case there the loop runs into a degenerated case an exit is possible (will generate degenerated face)
capFaceEdges.Clear();
capFaceEdgeSet.Clear();
var currEdge = e;
do
{
if (currEdge.IsValid)
{
capFaceEdges.Add(currEdge);
capFaceEdgeSet.Add(currEdge.Index);
}
// find next edge at start-vertex along plane
// the new cap face should have winding order start<-to becaues it is on the opposite of the current face-edge
currEdge = currEdge.FromVertex.Edges
.Select(x => x.FromVertexIndex == currEdge.FromVertexIndex ? x.Opposite : x)
.FirstOrDefault(x => x.IsAnyBorder && x.Index != currEdge.Index && vertexOnPlane[x.FromVertexIndex], PolyMesh.Edge.Invalid);
} while (currEdge.IsValid &&
currEdge.Index != e.Index &&
!capFaceEdgeSet.Contains(currEdge.Index));
if (capFaceEdges.Count > 2)
{
// add cap-face
foreach (var fe in capFaceEdges.Skip(1))
{
edges.Remove(fe.Index);
}
clippedMesh.AddFace(capFaceEdges.Select(fe => fe.ToVertexIndex).ToArray());
}
}
}
// clear topology (is invalid if face has been added)
clippedMesh.ClearTopology();
return(clippedMesh);
}
