private static bool compute_plane_curves(DMesh3 mesh, DMeshAABBTree3 spatial,
double z, bool is_solid,
out Polygon2d[] loops, out PolyLine2d[] curves)
{
Func <Vector3d, double> planeF = (v) =>
{
return(v.z - z);
};
// find list of triangles that intersect this z-value
PlaneIntersectionTraversal planeIntr = new PlaneIntersectionTraversal(mesh, z);
spatial.DoTraversal(planeIntr);
List <int> triangles = planeIntr.triangles;
// compute intersection iso-curves, which produces a 3D graph of undirected edges
MeshIsoCurves iso = new MeshIsoCurves(mesh, planeF)
{
WantGraphEdgeInfo = true
};
iso.Compute(triangles);
DGraph3 graph = iso.Graph;
if (graph.EdgeCount == 0)
{
loops = new Polygon2d[0];
curves = new PolyLine2d[0];
return(false);
}
// if this is a closed solid, any open spurs in the graph are errors
if (is_solid)
{
DGraph3Util.ErodeOpenSpurs(graph);
}
// [RMS] debug visualization
//DGraph2 graph2 = new DGraph2();
//Dictionary<int, int> mapV = new Dictionary<int, int>();
//foreach (int vid in graph.VertexIndices())
// mapV[vid] = graph2.AppendVertex(graph.GetVertex(vid).xy);
//foreach (int eid in graph.EdgeIndices())
// graph2.AppendEdge(mapV[graph.GetEdge(eid).a], mapV[graph.GetEdge(eid).b]);
//SVGWriter svg = new SVGWriter();
//svg.AddGraph(graph2, SVGWriter.Style.Outline("black", 0.05f));
//foreach (int vid in graph2.VertexIndices()) {
// if (graph2.IsJunctionVertex(vid))
// svg.AddCircle(new Circle2d(graph2.GetVertex(vid), 0.25f), SVGWriter.Style.Outline("red", 0.1f));
// else if (graph2.IsBoundaryVertex(vid))
// svg.AddCircle(new Circle2d(graph2.GetVertex(vid), 0.25f), SVGWriter.Style.Outline("blue", 0.1f));
//}
//svg.Write(string.Format("c:\\meshes\\EXPORT_SLICE_{0}.svg", z));
// extract loops and open curves from graph
DGraph3Util.Curves c = DGraph3Util.ExtractCurves(graph, false, iso.ShouldReverseGraphEdge);
loops = new Polygon2d[c.Loops.Count];
for (int li = 0; li < loops.Length; ++li)
{
DCurve3 loop = c.Loops[li];
loops[li] = new Polygon2d();
foreach (Vector3d v in loop.Vertices)
{
loops[li].AppendVertex(v.xy);
}
}
curves = new PolyLine2d[c.Paths.Count];
for (int pi = 0; pi < curves.Length; ++pi)
{
DCurve3 span = c.Paths[pi];
curves[pi] = new PolyLine2d();
foreach (Vector3d v in span.Vertices)
{
curves[pi].AppendVertex(v.xy);
}
}
return(true);
}