Rigify Retarget

Procedurally generates a duplicate of the selected armature with all the important deformation bones connected and with standard Rigify parameters defined (Which can modified to your liking before generation) which can be used for generating an animation ready armature that the original armature is then retargeted to, allowing to easily animate an armature of any type without having to modify the original armature or the weight painting of a model. The poses/animations made with the Rigify armature can then be baked into the original armature which can then be imported into Source.

If a character with shapekeys is defined before creation of the armature, shapekeys (Except ones that do not need it) will be divided into left and right and facial bones will be added onto the armature (Depending on which shapekeys are available) which will then be linked to the character's shapekeys through drivers, allowing you to modify a character's expressions within the armature without having to mess with any sliders (although this is not exportable). Since it modifies a character's shapekeys by adding a lot more, a backup of the character is used instead.

Aside from the retargeting, it works just like any other Rigify armature, with every bone in a certain layer which can be hidden after generation, with colors defining each of Rigify's bone types, and with properties that can be tweaked for different animation approaches and styles (Like IK stretch, toggling a pole for the arms and legs, toggle FK and the like), all of which are located in the Item tab in the viewport's right panel. If you want to know more about Rigify you can check its documentation.

Parameters

Retarget Constraints

Simply disables/enables the constraints that make the original armature follow the animation armature, which can come in handy to check if an animation was baked correctly.

Baking

Baking works through armature actions, meaning that in order to bake a pose onto the original armature, an action must be created onto the animation armature, you can bake either a single action (Which is either an action that has not yet been made into a strip, or a selected strip in the NLA editor) or all of the actions defined in the animation armature (Only the first action in each NLA track). Doing so will create a corresponding action, strip and track for the original armature in the NLA editor holding the baked animation data which can then be exported. Helper bones can also be baked although this is only necessary with viewmodels.

As a convenience feature, there is a function that allows to export every strip in the original armature's NLA editor (Blender Source Tools is required for this function) onto the location defined in said plugin's parameters.

Notes

The way retargeting works is by creating 2 empties (A base, and a target) for every bone, parenting the target empty to the base empty, connecting the base empty to the relevant bone in the animation armature, and then connecting the original armature's bone to the target empty. The drawback to this is that it, along with the widgets generated from Rigify can make it harder to search for objects since a lot of them are added onto the scene.

If the selected armature is a viewmodel, a camera will be created and constrained to the camera bone in the armature to mimic how the animations would look like in game, with an additional bone to control where the camera is pointing to. Lastly, the position of the animation armature's root bone is automatically lowered so the arms are at 0,0,0, although you can move it onto the original place if you like.