FBX Export: handle newly-added geometric transform inverse nodes.

This also tidies up the imported node structure a little,
by not adding the inverse nodes if there are no child nodes.

code/FBXConverter.cpp

@@ -215,24 +215,30 @@ void Converter::ConvertNodes( uint64_t id, aiNode& parent, const aiMatrix4x4& pa
                 // attach geometry
                 ConvertModel( *model, *nodes_chain.back(), new_abs_transform );
 
-                // now link the geometric transform inverse nodes,
-                // before we attach any child nodes
-                for( aiNode* postnode : post_nodes_chain ) {
-                    ai_assert( postnode );
+                // check if there will be any child nodes
+                const std::vector<const Connection*>& child_conns
+                    = doc.GetConnectionsByDestinationSequenced( model->ID(), "Model" );
 
-                    if ( last_parent != &parent ) {
-                        last_parent->mNumChildren = 1;
-                        last_parent->mChildren = new aiNode*[ 1 ];
-                        last_parent->mChildren[ 0 ] = postnode;
-                    }
+                // if so, link the geometric transform inverse nodes
+                // before we attach any child nodes
+                if (child_conns.size()) {
+                    for( aiNode* postnode : post_nodes_chain ) {
+                        ai_assert( postnode );
+
+                        if ( last_parent != &parent ) {
+                            last_parent->mNumChildren = 1;
+                            last_parent->mChildren = new aiNode*[ 1 ];
+                            last_parent->mChildren[ 0 ] = postnode;
+                        }
 
-                    postnode->mParent = last_parent;
-                    last_parent = postnode;
+                        postnode->mParent = last_parent;
+                        last_parent = postnode;
 
-                    new_abs_transform *= postnode->mTransformation;
+                        new_abs_transform *= postnode->mTransformation;
+                    }
                 }
 
-                // attach sub-nodes
+                // attach sub-nodes (if any)
                 ConvertNodes( model->ID(), *last_parent, new_abs_transform );
 
                 if ( doc.Settings().readLights ) {

code/FBXExporter.cpp

@@ -1775,7 +1775,10 @@ const std::map<std::string,std::pair<std::string,char>> transform_types = {
     {"ScalingPivotInverse", {"ScalingPivotInverse", 'i'}},
     {"GeometricScaling", {"GeometricScaling", 's'}},
     {"GeometricRotation", {"GeometricRotation", 'r'}},
-    {"GeometricTranslation", {"GeometricTranslation", 't'}}
+    {"GeometricTranslation", {"GeometricTranslation", 't'}},
+    {"GeometricTranslationInverse", {"GeometricTranslationInverse", 'i'}},
+    {"GeometricRotationInverse", {"GeometricRotationInverse", 'i'}},
+    {"GeometricScalingInverse", {"GeometricScalingInverse", 'i'}}
 };
 
 // write a single model node to the stream