Weights Extra allows you to easily export and import vertex group weights of skinned mesh to a JSON file.

It stores weight data based on vertex IDs along with mesh data so weights can also be imported to different meshes with different vertex count and topology. Import and export operations are done in world space, so you dont need to worry about transform values on the mesh or armature.

Import Methods

• Auto: Automatically chooses the best method for the imported mesh.
• Vertex ID: Matches and imports weights based on vertex IDs. Source and target meshes must be identical.
  
• Closest Vertex: Imports weights based on the closest vertex. Works best transferring weights from hi to low density mesh.
  
• Closest Point: Imports weights by calculating projected point on the closest triangle. Works best transferring weights from low to hi density mesh.

Maya Support
Weights extra supports maya ngSkinTools addon data format and allows exchanging weights between two addons.  Means that you can import ngSkin data to blender and import Weights Extra data to ngSkin. This exchange only support vertex ID transfer between identical meshes due to different coordinate systems.

Installing Addon
You can either unzip and copy weights_extra folder to your blenders addons folder or you go to blender preferences -> add-ons tab, click install and select weights_extra.zip file. Make sure Weights Extra addon is activated by searching its name on addons panel.

Tool Panel
When you activate Weight Paint mode, tool will show up at the bottom of Tool panel.

Exporting Weights
Click export button. It only exports vertex weights used by armature, all other vertex weights will be ignored.

Importing Weights
Click import button and select the import method if needed. Its default to 'Auto' and will pick best method that fits to current import scenario. It replaces only armature vertex groups, all other vertex groups stay intact.

API Methods
You can use its python api to import your own scrips.

from weights_extra import import_weights, export_weights

import_weights(object_name, filepath)

export_weights(object_name, filepath, method="AUTO") 
# method is optional, default is "AUTO", other options are "VERTEX_ID", "CLOSEST_VERTEX", "CLOSEST_POINT"

Please report any bug or request by contacting support at instantrig.com

Hope you find this tool useful, enjoy.