The article is reproduced from Unreal Engine . Please go to Unreal Engine to read the complete content.
This article will introduce you to one of the fundamentals of shooting professional content: motion capture systems . In the "Body Motion Capture Solutions and Settings" chapter, Movella's Xsens solution is introduced in detail, which can bring excellent quality to body capture and provide data for you to use throughout the production process. Its MVN software provides additional post-processing to clean data and eliminate slippage.
motion capture system
There are motion capture systems of varying costs on the market, with products using inertial systems being the cheapest. Optical capture systems typically cost upwards of $12,000, making them very expensive due to the larger capture volumes required.
Expensive systems come with more features and higher fidelity solver data. However, these systems often require more hardware and human resources, and can be complex to learn and use. Depending on what you ultimately want to create, decide which type of system is appropriate.
Body motion capture solutions and setups
This section introduces popular motion capture solutions and provides related setup guides.
Body motion capture solutions and setups
Physical motion capture refers to using specialized sensors to capture the movements and movements of actors, and then converting the captured content into digital data for animating virtual characters or objects.
There are many body motion capture solutions on the market at various price points that offer great value. This document only highlights some of the popular options, as optical options are beyond the price range of most studios. Common industry standard suites include Xsens launched by Movela.
streaming input
A common basic data streaming workflow for all motion capture suites is as follows:
1
Turn on the power and connect all required sensor hardware and straps.
2
These sensors are connected to corresponding vendor software to interpret motion into digital form.
3
Runs the corresponding vendor plug-in for a specific Unreal Engine version.
4
Add the plugin to Unreal Engine and restart the editor.
5
Use the Live Link protocol to send this stream to the IP address of the computer running Unreal Engine on your network.
6
In Unreal Engine, use the Live Link window "Add Live Link Source" for sinking.
7
A Retarget Asset Blueprint must be created for each skeleton that will receive motion capture data directly. This will map the incoming bone data to the appropriate bones for the selected skeleton.
(This is different for each motion capture vendor and each custom Unreal Skeleton, a custom T-pose is required for this step.)
8
Assign Live Link sources and redirect assets to your digital character’s skeleton.
9
If you don't see your actions at the editor level, add "Live Link Skeletal Animation" to your Blueprint in the Details panel.
10
watch the action
Offline processing and recording
As with all motion capture suites, the basic workflow for data streaming is as follows:
1
Turn on the power and connect all required sensor hardware and straps. Turn on the power and connect all required sensor hardware and straps.
2
These sensors are connected to corresponding vendor software to interpret motion into digital form.
3
Process and save this data locally on your computer or phone.
4
Export an .fbx animation file for import into Unreal Engine.
Xsens specifications
Xsens motion capture suite brings outstanding quality to body capture. This suite provides data you can use throughout the production process. Its MVN software provides some additional post-processing to clean the data and eliminate slippage.
Set up and calibrate official resources
1
body measurement
Body Measurement - Xsens Video Tutorial
https://tutorial.movella.com/video/body-measurements/
2
Connection kit
Preparing Hardware MVN Links - Xsens Video Tutorial
https://tutorial.movella.com/video/preparing-hardware-mvn-link/
3
Connect ASUS to computer
WPS Connection – Xsens Video Tutorial
https://tutorial.movella.com/video/wps-connection/
4
ALT connects ASUS router to computer
Asus Best Practices and Troubleshooting Techniques - Xsens Video Tutorials
https://tutorial.movella.com/video/link-router-setup-best-practices/
5
ALT connect to your home WiFi, skip ASUS router
Connect Link Body Pack to Home or Office Router - Xsens Video Tutorial
https://tutorial.movella.com/video/link-router-setup-best-practices/
6
WPS connection
WPS Connection – Xsens Video Tutorial
https://tutorial.movella.com/video/wps-connection/
7
Calibration Kit - T Pose Recommended for Unreal Engine
Calibration Link – Xsens Video Tutorial
https://tutorial.movella.com/video/calibrating-link/
Streaming to Unreal Engine Assets
Here are the official steps from the manufacturer for setting up the software and streaming:
https://base.xsens.com/s/article/MVN-Unreal-Live-Link-Plugin-UE5?language=en_US
Here's another reference that might be useful: Live Link for Unreal Engine - Xsens Video Tutorial
https://tutorial.movella.com/video/live-link-for-unreal/
This link is good for finding plugin versions for older versions of Unreal Engine, as well as a sample project containing the official MVN "puppet":
https://base.xsens.com/s/article/Unreal-MVN-Live-Link-Plugin-Overview?language=en_U
Here you can see the contents of a sample project with a nice compatible skeleton with and without finger bones. If you want to update your streamed actions to the highest quality the suite can provide, it's best to also use MVN puppet to import .fbx animations from MVN.
troubleshooting
If you don't see motion capture data in the Live Link window, double-click your IP address and port number. 9764 is the default, but if additional flows are added to MVN, the new port can be 9763.
If you see sliding/lifting in your Unreal Engine scene but it doesn't happen in MVN, it's probably because the proportions of the skeleton are different.
The repair steps are as follows:
-
Export .fbx with frame 0 as T pose from MVN
-
Create a new 1 frame animation from the first frame
-
Export this animation as a Skeletal Mesh
-
Reimport the Skeletal Mesh to use as the default puppet for all actions of this actor
Stream to MetaHuman
The recent addition of Live Link body and face variables (added to the master blueprint) makes it easier to place animations directly onto MetaHuman. Instead of creating a custom animation blueprint for the skeleton, you can directly select the corresponding Xsens source and check the "Use Live Link Body" box.
It's important to note that you need to open a Blueprint and set the Live Link body redirection variable. This is required to map the bone normally, but is not set as the instance editable and therefore is not exposed as a variable shown in the editor.
Likewise, if the character doesn't appear to be responding to incoming actions, adding the Live Link Skeletal Animation component will force the animation to update in the editor.
Note: The body proportions of your motion capture actor may be different from MetaHuman, so this method may introduce sliding steps that do not exist in the custom imported MVN .fbx on the official puppet. Advanced redirection can be used to fix this problem, as detailed in a future chapter.
Record and export in MVN
1
You may want to record test shots in the engine, as well as capture your test shots in MVN. MVN has a reprocessing step that will try to clean up data you wouldn't get from the engine.
2
Actions may need to be re-imported back into MVN for reprocessing.
3
The .fbx format exported from MVN will only contain animation data, not the skeletal mesh. Therefore, be sure to use the official MVN puppet skeleton in Unreal Engine as the base skeleton. This puppet is available from the official sample project file linked above.
4
In Unreal Engine 5.1, a new .fbx animation import option has been added. Make sure Snap to Closest Frame Boundary is checked. This should ensure a successful import at any sampling rate.
