Adding Extra Bones to Rigify

Some character have non-standard bones, e.g. a rigged hair. When we convert such a rig to Rigify, the rigified rig contains those bones, but they may be inconvenient to pose individually.

 

Here we have a figure with a rigged ponytail. The ponytail bones belong to the Custom collection.,

And here the rig has been converted to Rigify, with the hair bones still in the Custom collection. Posing each of hair bone individually can be done but is inconvenient.There are a few things that we can do to make it easier to pose the ponytail.

We can Add IK Goals. This tool is located in the Rigging > Chains panel which requires that the Rigging Tools feature is enabled.

Alternatively, we can Add Winders.

However, Rigify is a modular rigging system and we may want to use some of the Rigify types. Previously that has not been so easy to do. In principle we can first generate the metarig, then add the custom bones to it, and finally rigify the modified metarig. However, that requires further postprocessing because the vertex groups must be renamed. In the last version of the DAZ Importer there is a much simpler way. Just select a bone in the original DAZ rig and add a Rigify type to it.

Let us give the ponytail the control of a basic Rigify tail. Select the bone that we want to be the root of the tail, and assign a suitable Rigify type to it. Here we choose spines.basic_tail.

The Rigify Type panel contains various option for the bone chain. By default a basic tail can only bend along the X axis.

Once a bone has been assigned a Rigify type, it is added to the metarig together with its descendants. Any parent bones that are not part of the standard Rigify armature are also added.

Now the rigified armature has a ponytail with the extra control bones.

The entire ponytail can now be posed by rotating the target bone at the end of chain.

MHX Properties are now ID Properties

As discussed in the post on Custom Properties Cleanup, custom properties used by the DAZ Importer are now combined into a single, complex property. However, there are two exceptions:

1. Morph properties, because they are part of a web of drivers that would not be evaluated in the correct order if they were parts of a complex property.
2. Properties that need to work when the add-on is disabled, e.g. at a render farm.
   

 The custom properties used by the MHX rig belong to the second category. 

There are two types of custom properties in Blender:RNA properties and ID properties, or properties that are defined by the system or by add-ons and those that are created on the fly. The problem with RNA properties is that they do not work properly if the add-on is disabled. MHX properties have nevertheless been implemented as RNA properties, because ID properties did not worked with file linking in some earlier  version of Blender. This problem has been fixed in recent Blender versions, and therefore there is no reason to use RNA properties anymore.

This change should be backwards compatible, almost. Even if the MHX rig was created in an earlier version of the DAZ Importer, where the MHX properties were RNA properties, it should still function correctly with the latest version. This works because RNA properties are automatically converted to ID properties if the API no longer defines them. The only thing that does not work is animations with dynamic FK/IK switching.

Here are the custom properties of a recent MHX rig. The MHX properies begin with "Mha" (there was a reason why they don't start with "Mhx", but I don't remember why anymore). Note the cogwheel to the right of the property value. This indicates that we deal with ID properties rather than RNA properties, which would have "API Defined" written to the right instead. 

Pressing the cogwheel brings up the Edit Property window. Note that MHX properties are Library Overridable at the bottom of the window.

Save the scene with the MHX rig, open a new file, and link the collection with the MHX character into the new scene. To make the character useful in the new scene, choose Object > Library Override > Make.

We can still access the custom properties, but they can not be edited. When we change a linked property it turns green.

Now do the following steps:

1. Create an animation and save the file.
2. Disable the DAZ Importer and MHX RTS add-ons.
3. Restart Blender.
   

 We have now recreated the situation at a render farm, where the DAZ Importer and MHX RTS are not available. Nevertheless the animation works correctly, including the animation of custom properties needed e.g. for FK/IK switching.