Mirroring the Rig
Now that you have rigged one side of the character, you can duplicate or mirror it to the other side.
Naming Bones
Before mirroring the complete rig, you need to know that when the rig is finished, you’ll be able to copy poses and paste them mirrored and, by their names, Blender will recognize on which side of the rig those bones are located. Each bone has a name plus a suffix that tells Blender if that bone is on the left side or on the right side; for example:
Right side: C_hand.R (the .R suffix tells Blender this bone is on the right side).
Left side: C_hand.L (the .L suffix tells Blender this bone is on the left side).
Center: C_D_spine (when there is no suffix, Blender will know that bone is in the center).
This naming convention enables Blender to translate the pose from a bone on one side of the rig to the corresponding bone on the other side and, when you’re painting the weights for the skinning, Blender can mirror those weights to the other side of the rig as well.
Fortunately, Blender has tools to add those suffixes to the bones’ names automatically. Select all the bones in Edit or Pose Mode, press A, and, in the Armature or Pose menu (depending on the interaction mode in which you’re working) of the 3D View header, select the option AutoName Left/Right; this option will detect the bones that are on the positive or negative side of the X-axis and name them accordingly—that’s why it’s important that your character is centered on the X-axis.
After performing the AutoName operation, go to the bones that are in the center of the rig and check their names. Sometimes, the bones in the center of the rig are not exactly centered (X = 0) and so Blender also gives them suffixes. In this case, check their names and delete the suffixes.
Mirroring Bones
Here are the steps you need to follow to mirror the bones; they are similar to those you’d use to mirror meshes.
1. In Edit Mode, select all the bones of the rig, excluding the ones that are in the center (you can use a Box Selection by pressing B).
2. Press Shift + D to duplicate them and right click to cancel the movement.
3. Place the 3D cursor on the center of the scene (press Shift + C) and switch the pivot point to the 3D cursor by pressing . (period).
4. Press Ctrl + M to mirror the selected bones and press X to mirror them on the X-axis. Press Enter to accept.
5. The bones are now mirrored, but they have names like C_hand.L.001 because Blender automatically renamed them so there wouldn’t be two objects with the same name. With the right-side bones selected, go to the Armature or Pose menu on the 3D View header and select the Flip Names option. This will convert those duplicated names from the left side to be right-side names and it will get rid of the “001” suffixes; for example, C_hand.L.001 would become C_hand.R.
Adjusting Bones
Mirroring bones can save you a lot of work by adding constraints and performing repetitive tasks for both sides of the rig; unfortunately, however, mirroring has some side effects. After mirroring, you might need to make some adjustments.
When you mirror bones, some of them may be rotated in a weird way as an effect of inverting their X-axes and you’ll have to fix that manually, which can be time consuming but it’s usually less work than it would be to create both sides manually.
Here are some tips you can use for adjusting everything in the rig after the mirror has been done:
On the Armature tab of the Properties Editor, in the Display panel, you can enable the Axes option, which will display the orientations of bones in the 3D View. Using this helpful feature, you can compare the bone orientations between the right and left sides of the rig to see if some of them are off. To adjust rotation, use Ctrl + R in Edit Mode to make any necessary adjustments.
Some IK constraints may be off as well and you’ll probably need to change their Pole Angle Value in the IK constraint properties or adjust them in Pose Mode. Then you can apply those adjustments as a Rest Pose (Ctrl + A) to transfer them to the bones in Edit Mode.
A good way to determine if your rig is working properly is to test how it supports mirroring poses. If there’s something wrong with a bone on one side, when you mirror a pose, the corresponding bone on the other side will rotate differently and the pose won’t look the same side to side: then you’ll know that bone is not OK. Figure 11.7 shows the copy/paste options for poses.
Figure 11.7 You can copy and paste poses using the Copy/Paste buttons on the 3D View header when you’re working in Pose Mode.
Pose your character in Pose Mode, click the Copy Pose icon, and then click the Paste Mirrored Posed icon. If a bone doesn’t work properly, go back to Edit Mode and adjust the rotation of that bone with Ctrl + R.