[Bf-blender-cvs] [4e2a10352da] soc-2021-adaptive-cloth: adaptive_cloth: fix: mesh: flip edge: edge might already exist

[ishbosamiya]

Commit: 4e2a10352dad5c66fc638bb4d84c80954c5d011c
Author: ishbosamiya
Date:   Thu Aug 5 11:14:30 2021 +0530
Branches: soc-2021-adaptive-cloth
https://developer.blender.org/rB4e2a10352dad5c66fc638bb4d84c80954c5d011c

adaptive_cloth: fix: mesh: flip edge: edge might already exist

It is possible that there might already be an edge between ov1 and ov2
so it is best to not create a new edge between those because edges
between verts should always be unique for all the algorithms to work
correctly.

It is a case that shouldn't show up too often but when it does, it
will be interesting to see what happens in the static remeshing
part. The number of faces remains the same but number of edges can
change (reduce only).

===================================================================

M	source/blender/blenkernel/BKE_cloth_remesh.hh

===================================================================

diff --git a/source/blender/blenkernel/BKE_cloth_remesh.hh b/source/blender/blenkernel/BKE_cloth_remesh.hh
index e6b1c469037..b2c36698dd2 100644
--- a/source/blender/blenkernel/BKE_cloth_remesh.hh
+++ b/source/blender/blenkernel/BKE_cloth_remesh.hh
@@ -2242,7 +2242,7 @@ template<typename END, typename EVD, typename EED, typename EFD> class Mesh {
      * when across_seams is true:
      *
      * when across_seams is false:
-     * 2 faces, 1 edge
+     * 2 faces, might add 1 edge if no existing edge exists
      */
 
     /* Let `e` be the edge of `edge_index`
@@ -2285,24 +2285,30 @@ template<typename END, typename EVD, typename EED, typename EFD> class Mesh {
       auto ov1_index = ov1.self_index;
       auto ov2_index = ov2.self_index;
 
-      auto &new_e = this->add_empty_edge();
-      new_e.verts = {ov1_index, ov2_index};
-      this->add_edge_ref_to_verts(new_e);
+      /* Create the new edge only if there isn't already an edge
+       * between ov1 and ov2 */
+      if (!this->get_connecting_edge_index(ov1_index, ov2_index)) {
+        auto &new_e = this->add_empty_edge();
+        new_e.verts = {ov1_index, ov2_index};
+        this->add_edge_ref_to_verts(new_e);
+        added_edges.append(new_e.self_index);
+      }
 
       auto &new_f1 = this->add_empty_face(f1.normal);
       new_f1.verts = {v1_index, ov2_index, ov1_index};
       added_faces.append(new_f1.self_index);
       this->add_face_ref_to_edges(new_f1);
+      BLI_assert(this->is_face_edges_linked(new_f1));
 
       auto &new_f2 = this->add_empty_face(f2.normal);
       new_f2.verts = {v2_index, ov1_index, ov2_index};
       added_faces.append(new_f2.self_index);
       this->add_face_ref_to_edges(new_f2);
+      BLI_assert(this->is_face_edges_linked(new_f2));
 
       deleted_edges.append(std::move(e));
       deleted_faces.append(std::move(f1));
       deleted_faces.append(std::move(f2));
-      added_edges.append(new_e.self_index);
     }
     else {
       /* Do more expensive operation only if needed */
@@ -2314,6 +2320,15 @@ template<typename END, typename EVD, typename EED, typename EFD> class Mesh {
        * seam or boundary */
     }
 
+    BLI_assert(added_nodes.size() == 0);
+    BLI_assert(added_verts.size() == 0);
+    BLI_assert(added_edges.size() == 0 || added_edges.size() == 1);
+    BLI_assert(added_faces.size() == 2);
+
+    BLI_assert(deleted_nodes.size() == 0);
+    BLI_assert(deleted_verts.size() == 0);
+    BLI_assert(deleted_edges.size() == 1);
+    BLI_assert(deleted_faces.size() == 2);
     return MeshDiff(std::move(added_nodes),
                     std::move(added_verts),
                     std::move(added_edges),