Skin a mesh with Mannequin armature
The article explains how to skin a humanoid character with a Mannequin-compatible armature (skeleton). That will allow reuse of Mannequin animations for the character via animation retargeting in Unreal Engine 4.
This article purpose is to demonstrate the features of Chiro add-on for Blender. To achieve best results, you must do more than we cover in here. We do not correct weight paints nor set up morph targets. That is out of scope for this tutorial.
- Skin a mesh with Mannequin armature
- 1. Add Armature
- 2. Scale Armature
- 3. Adjust pelvis position
- 4. Adjust pelvis tail
- 5. Adjust spine_01
- 6. Adjust spine_02
- 7. Adjust neck and head
- 8. Adjust clavicles
- 9. Left Arm
- 10. Fingers
- 11. Left leg
- 12. Adjust the right side
- 13. Apply the pose as Rest Pose
- 14. Parent the armature
- 15. T-Pose
- 16. Apply the pose to mesh
- 16.5. (Optional) Snap clavicles
- 17. Fix bone rolls
- 18. Fix feet rotation
- 19. A-Pose
- 20. Export FBX
In this article we will skin a character mesh with a mannequin-compatible armature.
The mesh proportions are not matching the Mannequin, so we will change the bones and later use retargeting manager in Unreal Engine 4 to make the animation work. The mesh does not have armature, vertex groups and weight paints.
Here is the character we will be skinning
1. Add Armature
The first step is to add the armature we'll be working with. To do that, find the menu and the armature to the scene. It will be easier to work if we make it show up "In Front", so let's do it straight away.
Add -> Armature -> Chiro (UE4 Mannequin) -> A-Pose
Armature sidebar -> Viewport Display -> In Front
It does not matter if you start with the armature in A-Pose or T-Pose.
In this example we start with A-Pose merely because it's closer to the mesh posture.
2. Scale Armature
Now we scale the armature so its spine length following the torso size accordingly.
Here are a couple guidelines you could follow to make it right
- pelvis root should be at the top of the groin
- clavicle bone tails should be just in the middle of the character shoulders
If you cannot find good alignment, then don't align clavicles, just make sure pelvis is in the correct position. In the following steps we will adjust all the bones one by one anyway, but it is important to begin with the pelvis in the right spot.
3. Adjust pelvis position
Now we shall adjust the bone positions. However, pelvis is the root for all the other bones
and it is important that we begin with it first.
To find the correct position for pelvis, you could follow these guidelines.
- front view: top of the groin, middle of the mesh
- side view: middle of the mesh, middle of glutes
- rear view: middle of glutes, middle of the mesh
To make it easier, in this step we will move pelvis into a separate layer,
so the other bones don't obscure the view. To do that, we are switching to the
Then, we return to the
Object Mode and adjust the pelvis position by dragging the armature around.
4. Adjust pelvis tail
The rest of the bones we will adjust in
Now we are correcting
spine_01 position by following these guidelines
- front view: just below navel
- side view: middle of the mesh
- rear view: just above the pelvis
Since the bones are connected, to adjust
spine_01 position we will update the
pelvis bone instead.
Pose Mode we will rotate
pelvis and increase its
5. Adjust spine_01
Same here. To adjust
spine_02 we will update
Pose Mode. Rotate the bone and
Scale Y to change the bone length.
Here are the guidelines for
- front view: celiac plexus (aka solar plexus), just below the ribcage, top of the abdomen
- side view: middle of the mesh
To do this, we will move the
spine_01 bone to the current layer via
6. Adjust spine_02
Repeating the same proceduce to adjust
- front view: middle of the chest
- side view: middle of the mesh, below the bottom of armpit, following the shape of the mesh
To move the bone into current layer we're using shortcuts (
If you're not comfortable with shortcuts, you could repeat the UI actions from the previous steps.
The shortcuts are doing the same thing.
7. Adjust neck and head
Repeating the procedure for
neck root guidelines:
- front view: root of the neck, above clavicles
- side view: root of the neck, just above the shoulders
neck tail guidelines:
- side view: behind the jaw, below the ear
- parallel to face
8. Adjust clavicles
The clavicle bones are the most error prone in retargeting Mannequin animations. Most likely you won't be able to find the correct position for your character from the first try. The shoulders may look broken, or positioned weirdly. To mitigate that effect, find a correct spot for clavicle bone roots. Although, for now, we are going to leave it "as is".
Later we may use the "auto-detection" provided by the addon via Snap clavicles to Mannequin position transformation. It won't give you the best possible result, but it is "good enough" to begin with.
- turn on X-mirror
- do not change clavicle root position
- clavicle tail should be placed in the middle of the shoulder joint
9. Left Arm
Following the procedure, we're leaving X-mirror turned on and update the left arm bones.
Here are some simple guidelines for that
- all bones should be placed in the middle of the mesh
upperarm_l tailshould be placed exactly at the elbow joint
lowerarm_l tailshould be placed exactly at the wrist joint
hand_l tailshould be placed at the root of the middle finger
Skin the fingers right is tricky. Although, if you're careful enough, the result should be good.
Here are the guidelines for you:
hand_lbone to find the correct
thumb to pinkyposition
- drag roots of gingers, place them to match knuckles
- rotate the rest finger bones to find correct finger positions
- scale the bones to match finger phalanges
- make sure X axis of every bone except thumb looks the same way as the palm
We are still using X-mirror and only dealing with the left hand.
11. Left leg
Now we're ready to proceed with legs.
The guidelines are:
thigh_l rootshould be already in a good position, so we don't touch it
thigh_l tailshould be placed in the knee joint
calf_l tailshould be placed at the ankle joint
foot_l tailshould be placed at the beginning of the toes
ball_lshould be aligned straight forward
We're still using X-mirror and only adjust left leg bones.
In the process we're also using Select Bone Group: Twist Bones to select all twist bones and move them into a different layer, so they don't obscure the view.
12. Adjust the right side
Ideally the mesh will by symmetrical along the X axis. However, the world is not ideal, so we should account for the differences between the left and right sides of the mesh.
- Turn OFF X-mirror
- Correct right arm, palm, fingers and leg
13. Apply the pose as Rest Pose
We have the armature in the correct pose precisely following the mesh posture and proportions.
Now we need to apply all our changes to the armature by applying the pose as Rest Pose.
14. Parent the armature
It is time to parent the mesh with the armature. Ideally you may like to amend the weight paints for the vertex groups, but for the brevity of this tutorial we will use auto-weights and leave it as is. This will give us good enough result for now.
A requirement for the armature to be mannequin-compatible is correct bone rolls.
The Chiro add-on has built-in functionality to correct the rolls. However, to do so properly it needs the character to be in T-Pose. Thus, we will put our mesh into T-Pose now.
Here are the guidelines
- Face: looking straight forward, head is aligned by Z axis
- Feet: looking straight forward, parallel to the floor
- Arms: aligned by X axis, parallel to the floor
- Upper arms: parallel to the floor
- Elbows: looking straight back (towards Y axis)
- Palms: parallel to the floor
16. Apply the pose to mesh
Before we move on, we need to put the mesh into the new T pose at rest. To do so, we will use Apply Pose to Mesh & as Rest feature. Without it, the mesh will keep its original form and not the T-Pose we've just made for it.
Pose -> Apply -> Apply Pose to Mesh & as Rest (Chiro)
16.5. (Optional) Snap clavicles
This step is optional, because it may have different results depending on the character. Sometimes it may help with shoulders, sometimes it would make things worse. You should try both ways and choose the best option that suits your character anatomy.
If you are skinning your character for the first time, we are recommending to skip this step
and come back later to try this option if you find that your character shoulders aren't looking
We also encourage you to save the progress you've made so far in a separate blend file, so you could come back to this step later and rework not from the very beginning, but from this step.
To do that we will use Snap clavicles to Mannequin position transformation.
Find and press in the menu:
Armature -> Chiro (UE4) -> Mannequin --> Snap clavicles to Mannequin position
17. Fix bone rolls
Now we should be able to correct the bone rolls via the Bone Roll T-Pose transformation.
- Switch to
Armature -> Chiro (UE4) -> Mannequin --> Bone Roll T-Pose
18. Fix feet rotation
The Bone Roll T-Pose transformation will try to detect the best rotation. However, depending on the actual mesh pose, it will not be correct for some bones. Particularly, if the feet of the mesh don't look straight forward, the roll may be incorrect.
Not a big problem. We can fix the rolls manually. To do that:
- Make sure X-Mirror is turned OFF
- fix the left foot roll so X axis looks down
- fix the right foot roll so X axis looks up
If your mesh has asymmetry, X-mirror will dislocate the bones, this is why we turn it off
In this video, we're hiding the obstructive bones by selecting them and pressing
H on keyboard.
To unhide them later you can press
The final step before it's ready for exporting. The add-on Export FBX operator relies on the armature to be in A-Pose to correct the bone rotations and make it compatible with the Mannequin armature. Thus, the last step before exporting is to pose it into A-Pose and apply it to the mesh. Similar to what we did with T-Pose before.
- Go to
- Find and press in menu
Pose -> Re-Pose (Chiro UE4) -> "Mannequin --> A-Pose"
- Find and press in menu
Pose -> Apply -> Apply Pose to Mesh & as Rest (Chiro)
20. Export FBX
Now it is ready for exporting to FBX. However, the add-on has its own Export FBX operator, that uses correct export settings and takes care about some extra stuff that you rarely want to do manually. For more details on the Export FBX operator, see its own documentation section.
Export FBX operator saves files into the same folder with your current .blend file.
If your project was not saved on disk, the export menues will be inactive (greyed out).
The export may take some time. Wait until the dropdown disappears from the screen.
If the proportions of your character are exactly the same as Mannequin (e.g. you did not update any bone scales, only rotations), you might import it with the Mannequin skeleton and reuse animations with no retargeting required. If the proportions are different, you will need retargeting.
File -> Export -> FBX (Chiro UE4 Mannequin) -> Save as ***.fbx
The resulting FBX file is ready for use in Unreal Engine 4 with default import settings.
Although, most likely it will need animation retargeting in Unreal Engine 4. If you are not sure how to do that, read HowTo: UE4 Retargeting.
These results are not ideal, because we did not do manual weight painting and mesh correction.
The goal is to show you what the add-on is capable of, not to teach how to skin characters professionaly.