filter.splitCuts splits "C" edges into "B" edges (fix #46)

* Renamed from `filter.cutEdges`.
* New default of cutting all edges assigned `"C"`.
* `filter.cutEdges` and `filter.joinEdges` now return arrays of all
  edges assigned `"C"` and `"B"` respectively.

dist/fold.js

@@ -310,6 +310,8 @@ convert.faces_vertices_to_edges = function(mesh) {
   Given a FOLD object with just `faces_vertices`, automatically fills in
   `edges_vertices`, `edges_faces`, `faces_edges`, and `edges_assignment`
   (indicating which edges are boundary with 'B').
+  This code currently assumes an orientable manifold, and uses nulls to
+  represent missing neighbor faces in `edges_faces` (for boundary edges).
   */
   mesh.edges_vertices = [];
   mesh.edges_faces = [];
@@ -676,6 +678,14 @@ filter.unassignedEdges = function(fold) {
   return filter.edgesAssigned(fold, 'U');
 };
 
+filter.cutEdges = function(fold) {
+  return filter.edgesAssigned(fold, 'C');
+};
+
+filter.joinEdges = function(fold) {
+  return filter.edgesAssigned(fold, 'J');
+};
+
 filter.keysStartingWith = function(fold, prefix) {
   var key, results;
   results = [];
@@ -1306,7 +1316,7 @@ filter.addEdgeAndSubdivide = function(fold, v1, v2, epsilon) {
   return changedEdges;
 };
 
-filter.cutEdges = function(fold, es) {
+filter.splitCuts = function(fold, es = filter.cutEdges(fold)) {
   var b, b1, b2, boundaries, e, e1, e2, ev, i, i1, i2, ie, ie1, ie2, k, l, len, len1, len2, len3, len4, len5, len6, len7, len8, m, n, neighbor, neighbors, o, q, r, ref, ref1, ref10, ref2, ref3, ref4, ref5, ref6, ref7, ref8, ref9, t, u1, u2, v, v1, v2, ve, vertices_boundaries, z;
   if (!es.length) {
     /*
@@ -1320,6 +1330,9 @@ filter.cutEdges = function(fold, es) {
     `FOLD.convert.edges_vertices_to_faces_vertices_edges`),
     and recomputes `vertices_vertices` if present,
     but ignores face properties.
+    `es` is unspecified, cuts all edges with an assignment of `"C"`,
+    effectively switching from FOLD 1.2's `"C"` assignments to
+    FOLD 1.1's `"B"` assignments.
     */
     return fold;
   }

doc/api.md

@@ -61,7 +61,7 @@ for details.
   If the edge is a loop, the returned arrays are empty.
   If the edge is a duplicate, the first array has the old edge index and the
   second array is empty.
-* `FOLD.filter.cutEdges(fold, es)`:
+* `FOLD.filter.splitCuts(fold, [es])`:
   Given a FOLD object with `edges_vertices`, `edges_assignment`, and
   counterclockwise-sorted `vertices_edges`
   (see `FOLD.convert.edges_vertices_to_vertices_edges_sorted`),
@@ -72,6 +72,9 @@ for details.
   `FOLD.convert.edges_vertices_to_faces_vertices_edges`),
   and recomputes `vertices_vertices` if present,
   but ignores face properties.
+  If `es` is unspecified, cuts all edges with an assignment of `"C"`,
+  effectively switching from FOLD 1.2's `"C"` assignments to
+  FOLD 1.1's `"B"` assignments.
 * `FOLD.filter.transform(fold, matrix)`:
   Transforms a FOLD object by a given transformation `matrix` (generated by
   `FOLD.geom.matrix...`), in particular transforming `vertices_coords`

src/filter.coffee

@@ -13,6 +13,10 @@ filter.boundaryEdges = (fold) ->
   filter.edgesAssigned fold, 'B'
 filter.unassignedEdges = (fold) ->
   filter.edgesAssigned fold, 'U'
+filter.cutEdges = (fold) ->
+  filter.edgesAssigned fold, 'C'
+filter.joinEdges = (fold) ->
+  filter.edgesAssigned fold, 'J'
 
 filter.keysStartingWith = (fold, prefix) ->
   key for key of fold when key[...prefix.length] == prefix
@@ -338,7 +342,7 @@ filter.addEdgeAndSubdivide = (fold, v1, v2, epsilon) ->
   changedEdges[1].push changedEdges2... if changedEdges2?
   changedEdges
 
-filter.cutEdges = (fold, es) ->
+filter.splitCuts = (fold, es = filter.cutEdges(fold)) ->
   ###
   Given a FOLD object with `edges_vertices`, `edges_assignment`, and
   counterclockwise-sorted `vertices_edges`
@@ -350,6 +354,9 @@ filter.cutEdges = (fold, es) ->
   `FOLD.convert.edges_vertices_to_faces_vertices_edges`),
   and recomputes `vertices_vertices` if present,
   but ignores face properties.
+  `es` is unspecified, cuts all edges with an assignment of `"C"`,
+  effectively switching from FOLD 1.2's `"C"` assignments to
+  FOLD 1.1's `"B"` assignments.
   ###
   return fold unless es.length
   ## Maintain map from every vertex to array of incident boundary edges