Posing and Animating the Hands

You have 2 possible options to pose and animate the Hands. You can use the FK Constrained Rig(default) or you can use the FK Simple Rig.

Both Rigs have very different advantages:

With the FK Constrained rig you can setup realistic hand poses in a very short time with just a few clicks. But you can not create every possible pose.

With the FK Simple rig you can pose each finger bone individually with no restriction, but you also can mess up the pose easily.

FK Constrained Rig

With the FK Constrained Rig you typically select only the first bones of the fingers (in red) and rotate those bones along the local X axis (by typing ‘R’ for rotate followed by 2 ‘x’ for local x axis)

All other finger bones will automatically curl up following the rotations of the first finger bones. The rig is constructed so that when you select all first fingers (and first thumb bones) then R xx will open and close the hand in a reasonable way.

Of course you can rotate each finger to a different angle to place the hands into a variety of poses. You also can select the second and third fingers and rotate them as well, either all together or one by one. The FK Rig tries to keep the hand pose always realistic.

FK Simple Rig

If you want to create very detailed and special poses then you can use the FK Simple Rig. Here you will pose each finger bone individually.

this mode allows you to place each bone of each finger in exactly the way you want.

Never mix FK Constrained and FK Simple

When you rotate the fingers individually and then switch from FK Simple to FK Constrained then the constraints will result in additional rotations.

In the image aside i tried to visualize what happens. Here the finger bones get rotated much more than anticipated as soon as you switch to FK Constrained.

Caveat: Sometimes you do not see that your finger rotations actually are getting too large until you  store the blend file and reload it. The reason for this is that the auto FK is not always applied immediately on top of the already existing rotations when you switch the mode. Because of this we strongly recommend that you either use the FK Constrained mode or the FK Simple mode and never mix both modes.

Adjusting the Hand Rig to Custom meshes

In this chapter we will focus on custom hands. I am using a slightly modified version of the avamesh model here. If you want to follow this document, then you can prepare your scene as follows:

  • Open the Avastar Tab
  • Open the Devkit Manager panel
  • click on Avamesh – female
  • Select the mesh
  • open the Skinning Panel
  • Unbind from Armature

Now you have the starting model.

Note: Please use Avastar-2.3-8 or newer. You may find this version in your daily builds download folder

Adjust the hand rig

  • Add a new extended Avastar (Only Rig)
  • Make sure the rig i selected in Pose mode
  • Open the Rig Display panel
  • Make hands and arms visible
  • Set Hand Constraints to FK Simple

  • Now adjust the rig to one hand

Make sure you work on the green animation bones!

Begin in top view, only use rotation. do not use translation or scale. You may rotate the steel blue structure bones as well.

After some tweaking …

 

switch to side view and adjust the fingers again. Lets do the fingers first. For the thumb we need to do a bit of special tweaking…

Now all fingers are correct, but the thumbs still need a bit of tweaking. For this we need to know about 2 special control bones. …

 

Here i have enabled Bone shapes. This may help to understand how the bones operate:

  • The Thumb Controller rotates the thumb around the Wrist bone (use “R” )
  • The Thumb0 controls the angle between Thumb0 and Wrist bone (“R”)

Finally the hand rig is adjusted for one side of the character.

 

 

  • Select all adjusted hand bones
  • Copy them to the pose buffer
  • Mirror paste them to the other side

 

You can select the entire hand by using ‘B’ and drag. At the end both hands should be aligned to the hand mesh. Inspect this carefully before you proceed!

And note: For now we only have a pose.
Next we will make this our new Default Rig!

Create a new Restpose

  • Select the Armature in Pose mode
  • Make Sure you are in Expert mode
  • Open the Posing Panel
  • Convert to Bind Pose

Since we have no meshes assigned yet the mesh conversion is not relevant. Just keep the defaults, it does not hurt.

Now we have defined a new Restpose and we can use this pose all the time from now on. But note: This is a bind pose.

  • Open the Appearance panel
  • Enable the Use bind Pose option

Bind the Mesh

This is an opportunity to show you a nice little trick. We are only interested in getting the weights for the hands. We want to use weight from Bones, but we also want to only weight the hands and keep the rest  of the mesh untouched. Here is how it goes:

  • Select the Armature
  • SHIFT Select the Mesh in Object mode
  • Then go to Edit mode
  • And select the hand vertices

 

  • Open the Skinning panel
  • Set the options:
    • Weight from Bones
    • Clear Weights
    • Only operate on selected weights
  • Now Bind to Armature