Merge pull request #2430 from Hugo-Pereira/fix_assimp_export_consistency

[FBX Export] fixed ordering of skin indices and weights, to be consistent between systems

code/FBXExporter.cpp

@@ -1575,19 +1575,30 @@ void FBXExporter::WriteObjects ()
     // one sticky point is that the number of vertices may not match,
     // because assimp splits vertices by normal, uv, etc.
 
+    // functor for aiNode sorting
+    struct SortNodeByName
+    {
+        bool operator()(const aiNode *lhs, const aiNode *rhs) const
+        {
+            return strcmp(lhs->mName.C_Str(), rhs->mName.C_Str()) < 0;
+        }
+    };
+
     // first we should mark the skeleton for each mesh.
     // the skeleton must include not only the aiBones,
     // but also all their parent nodes.
     // anything that affects the position of any bone node must be included.
-    std::vector<std::set<const aiNode*>> skeleton_by_mesh(mScene->mNumMeshes);
+    // Use SorNodeByName to make sure the exported result will be the same across all systems
+    // Otherwise the aiNodes of the skeleton would be sorted based on the pointer address, which isn't consistent
+    std::vector<std::set<const aiNode*, SortNodeByName>> skeleton_by_mesh(mScene->mNumMeshes);
     // at the same time we can build a list of all the skeleton nodes,
     // which will be used later to mark them as type "limbNode".
     std::unordered_set<const aiNode*> limbnodes;
     // and a map of nodes by bone name, as finding them is annoying.
     std::map<std::string,aiNode*> node_by_bone;
     for (size_t mi = 0; mi < mScene->mNumMeshes; ++mi) {
         const aiMesh* m = mScene->mMeshes[mi];
-        std::set<const aiNode*> skeleton;
+        std::set<const aiNode*, SortNodeByName> skeleton;
         for (size_t bi =0; bi < m->mNumBones; ++bi) {
             const aiBone* b = m->mBones[bi];
             const std::string name(b->mName.C_Str());
@@ -1728,7 +1739,7 @@ void FBXExporter::WriteObjects ()
         aiMatrix4x4 mesh_xform = get_world_transform(mesh_node, mScene);
 
         // now make a subdeformer for each bone in the skeleton
-        const std::set<const aiNode*> &skeleton = skeleton_by_mesh[mi];
+        const std::set<const aiNode*, SortNodeByName> skeleton= skeleton_by_mesh[mi];
         for (const aiNode* bone_node : skeleton) {
             // if there's a bone for this node, find it
             const aiBone* b = nullptr;