Rigid Body Solving: Text Documentation

Rigid Body Solving

Note: When doing a rigid bodies setup, do not pause playback in Motive. Only play the range when the actor is in its desired pose and once the data is imported to the IKinema Rig you can go back to playing the entire data.


The first step is to import a character fbx into the Unreal Content Browser

1: Right click on your character's skeleton (figure 1)

Figure 1 


2: Go to IKinema Rig Actions 

3: Select Create IKinema Rig

4: Open the newly created IKinema Rig (figure 2)

Figure 2

Delete any excess bones your character may have that you do not want to retarget to (figure 3). These are usually eye joints, finger and etc.

Figure 3

Remember that deleting any bones in the IKinema rig only removes them from being retargeted on.

Next is to import the Mocap data that's being streamed

Fill in the fields in the 'MoCap Source' parameter (figure 4). An explanation for the fields is available below the figure.

Figure 4

Source: Your chosen Mocap System.

Matching Template: Select If you have a mapping template you’ve previously saved and wish to use it again in this setup. Otherwise, leave blank and IKinema’s default template will be used.

Server Address: Address of the machine you are using to stream. To learn how to find your Server Address click here and scroll to the bottom of the page.

Server Port: This is set in your chosen Mocap system. 

Subject Name: For Rigid body streaming, set the name to "Rigid_Bodies"

Import Scale: The scale your data is being imported at. You’re able to adjust this value to get a better match between your source and target character.

Streaming Y-up: Check box if your Mocap system is streaming Y as its up axis.

Zero Source Rotation: Import your stream in a T-Pose (Currently only available for OptiTrack’s Motive and XSens MVN).

Import Rigid Bodies: Check this box if you are streaming rigid bodies.

Before pressing ‘Import Actor’ make sure your rigid body data is in a basic pose, like a T-pose or A-pose


Once you are done make sure you have ticked ‘Import Rigid Bodies’ and press 'Import Actor' (figure 5)

Figure 5

Your Rigid Bodies will then be imported (figure 6).

Figure 6

Match up your target skeleton to your rigid bodies. When matching the legs and arms make sure you have a bend in the elbows and knees (figure 7). Please refer to figure 8 for reference to the matching.

Figure 7


Figure 8

When your matching is done:

1: Select a Rigid Body and the select it corresponding bone from the hierarchy (figure 9)

Figure 9

2: Right-click on the selected bone select ‘ Link Bones’ (figure 10)

Figure 10

3: Right-click again while still having the rigid body and bone selected. This time go ‘Constraint Task’ and pick its corresponding task (figure 11)

Figure 11

Done correctly it should create a task like in figure 12

Figure 12

If you get the error in figure 13, then the rigid body hasn’t been linked to the selected bone.

Figure 13

When creating a task for the head, it's better to use the ‘chest task’ and not the ‘head task’ (figure 14).  However, if you wish to use the head task you will need to enable location in the task's settings.

Figure 14

With the feet rigid bodies, you need to link their rigid bodies with three different bones.

These are the foot bone, toe bone and knee. Use a foot task for the toe and feet and a knee task for the knee (figure 15).

Figure 15

Please refer to figure 16 and figure 17 for more information on task location.

Figure 16

Figure 17

Now go back to the Unreal content browser and create an ‘Animation BluePrint’ (figure 18):

1: Right-click on the content browser

2: Go ‘Animation’

3: and create an Animation BluePrint

Figure 18

4: Select the target skeleton (figure 19)

Figure 19

5: Rename and open it

Once the Animation BluePrint is open we will need to create two extra nodes. These are 'Mocap Stream' (similar to the one in the IKinema Rig Editor)and the IKinema Rig we made for our character.

In the ABP right click and create a node called ‘MoCap Stream’ (figure 20)

Figure 20

This is the same parameter we had filled out earlier in the IKinema Rig Editor, fill it out with the same information as before.

Set the Actor (figure 21). The Actor skeleton (figure 22) is created during the setup stage in the IKinema Rig Editor.

Figure 21

Figure 22

Set the ‘MoCap Server’ (figure 23)

Figure 23

Scroll down and tick the ‘Use Rigid Bodies’ and set the import scale (figure 24)

Figure 24


Import Scale:

OptiTrack Motive: 100

XSens MVN: 100

Vicon Blade: 0.1

Next, right-click and search ‘Retargeting using IKinema rig’ then followed by the name of your rig (figure 25).

Figure 25

Everything should be retargeting now. However, there will be some issue with the retargeting and movement of the joints (figure 26). To sort this out and get a high-quality result you will need to go back to the IKinema rig editor and adjust the bone and constraint parameters for your character.

Figure 26

Open the IKinema Rig Editor.

The main bones which will most likely need their parameters value adjusted are the spine, neck, arms and legs (figure 27). The main parameters that will need adjusting for these bones are the weight, retargeting gain, retargeting DoF gain and Degrees of freedom (DoF).

Figure 27

Once your done adjusting the bones parameter, go to constraint mode (figure 28).

Figure 28

Any of the constraints might need their parameters adjusted. The parameters that will most likely need to be adjusted are Position and rotation weight, position and rotation DoF, position and rotation depth (figure 29).

Figure 29

You will need to go through some trial and error to get parameters working for your set up.

But once done, your all done (figure 30).

Figure 30

If you're having any issues please visit our FAQ Page.