Close CageFork properly

README.md

@@ -5,7 +5,10 @@
   behind this.
   
 ## Annoying/boring
-- Make branching properly close the final boundaries.
+- Fix non-manifold bug at branch. (The edges must be *shared*. It is
+  not sufficient that the subdivided edges both lie incident on some
+  other edge and cover it completely. You must subdivide that larger
+  edge, and thus the triangle it lies on.)
 - https://en.wikipedia.org/wiki/Polygon_triangulation - do this to
   fix my wave example!
   - http://www.polygontriangulation.com/2018/07/triangulation-algorithm.html

cage.py

@@ -109,7 +109,8 @@ class CageGen(object):
                 # We stop recursing here, so close things off if needed:
                 if close_last:
                     for poly in cage_last.polys():
-                        meshes.append(meshutil.close_boundary_simple(poly))
+                        meshes.append(meshutil.close_boundary_simple(poly, reverse=True))
+                    # TODO: Fix the winding order hack here.
                 break
             # If it's a fork, then recursively generate all the geometry
             # from them, depth-first:
@@ -119,7 +120,7 @@ class CageGen(object):
                 # (e.g. loop with fork)
                 for gen in cage_cur.gens:
                     m = gen.to_mesh(count=count - i, flip_order=flip_order, loop=loop,
-                                    close_first=False, close_last=False,
+                                    close_first=False, close_last=close_last,
                                     join_fn=join_fn)
                     # TODO: How do I handle closing with CageFork?
                     meshes.append(m)

meshutil.py

@@ -241,13 +241,17 @@ def join_boundary_optim(bound1, bound2):
     i = numpy.argmin(errs)
     return join_boundary_simple(bound1, numpy.roll(bound2, i, axis=0))
 
-def close_boundary_simple(bound):
+def close_boundary_simple(bound, reverse=False):
     # This will fail for any non-convex boundary!
     centroid = numpy.mean(bound, axis=0)
     vs = numpy.concatenate([bound, centroid[numpy.newaxis,:]])
     n = bound.shape[0]
     # note that n is new the index of the centroid
     fs = numpy.zeros((n+1, 3), dtype=int)
-    for i in range(n):
-        fs[i] = [i, n, (i+1) % n]
+    if reverse:
+        for i in range(n):
+            fs[i] = [(i+1) % n, n, i]
+    else:
+        for i in range(n):
+            fs[i] = [i, n, (i+1) % n]
     return FaceVertexMesh(vs, fs)