The Mirror Weights window is a fast way to reflect weighting values from one side of your mesh to another. While the Save/Load Weight window does let you mirror weights, the Mirror Weights window does not require an external file. It uses a simpler closest point algorithm for matching points, and so is faster, but it works best when the mesh sides are symmetric or close to symmetric.

Like the other weight tools, Mirror Weights can operate on the entire mesh, or only on selected points.

To mirror weights for a mesh

1. Select Muscle > Weighting > Mirror Weights from the main menu bar.

   The Mirror Weights window appears.

2. Select the mesh you want to mirror weights for and click to load it into the window.
   Tip -click the Node field to select from a list of Muscle deformed objects in the scene.
3. Select the weight type you want to mirror from the Weights drop-down list.
4. Select the position to use during mirroring. World Pos. uses the world position of the mesh, Local Pos. uses the object position.
5. Specify the Point Position Match Tolerance.

   Since points on the opposite side are matched by position, this specifies how far they can be and still be determined as a match. Larger values means they are more likely to find a match. A smaller value is more precise. The default tolerance is -1, which means that the closest point will match regardless of distance.

   Tip -click the Tolerance field to bring up several default settings.
6. Set the direction to mirror across. This defaults from +X to –X, setting weights for points on the –X side.
7. Enter the Search/Replace string for your naming conventions. In order to properly mirror influence-based weights such as Sticky weights, your muscles/bones should be named with some sort of naming convention. For example, if your left side muscles use _L at the end, and the right use _R, set the _L as the Search and _R as the Replace when mirroring from the left to the right sides.
   Tip -click the Search field to bring up several common naming conventions.
8. Select any points you want to load weights for. If no points are chosen, all points on the mesh for the side you are mirroring to are used.
9. Click Mirror Weights. The weights are mirrored from one side to the other.