An important parameter in the Muscle Mirror node is the group setting, which controls which muscles get mirrored. Incorrect group configuration may cause central muscles to be duplicated, which will break attachment constraints in the muscle solver.

The node has a few key parameters to control the mirroring behavior. You can adjust the From/To prefix to control naming conventions, by default it will convert L_ prefixes to R_ for the mirrored geometry, but if you have a different naming convention, or different side to mirror, you can change these as needed.

When mirroring constraints, there are three primary types of detail attributes:

• musclegluedict for all Muscle glue constraints

• muscletobonedict for all Muscle to bone constraints

• muscletomuscledict for all Muscle to muscle constraints.

The mirroring process duplicates entries in each of the above attributes for left side muscles and replaces L_ prefixes with R_ in the duplicates. For central muscles, those with a C_ prefix, the node preserves the entries without duplication while maintaining proper constraint relationships between mirrored pairs.

After creating your mirrored muscles, you can use Muscle Constraint Properties Vellum SOP node to verify that the constraints were mirrored correctly:

1. Create a Muscle Constraint Properties Vellum SOP node after your Muscle Mirror SOP.

2. Connect your bone geometry to its second input.

3. Select the checkbox for Enable All to turn it on. This helps to preview your constraints without making any unwanted changes to them.

4. Toggle between the Muscle to Muscle and Muscle to Bone tabs to check that the mirror looks correct.

5. If one side shows tangled or incorrect constraint connections, check the Group parameter in your Muscle Mirror SOP. You may need to exclude central muscles that shouldn’t be mirrored.