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Movement Analysis

Here’s how real-time feedback in Cortex works

20 Apr 2023

When conducting real-time motion capture (for training, research, animation or other purposes), it helps to understand whether a required movement is performed correctly for its use case, and to get that insight directly while the action is carried out. To do that, a feedback indicator can alert the system operator whether the exact motion has been exhibited, as soon as it happens.

We’ve received a lot of interest from users of our Cortex software to better understand how to use real-time feedback in the platform, with this useful functionality built in. While it is possible to send captured data to third parties, BioFeedTrak in Cortex instead allows you to set up a range of desired feedback loops to suit your needs. 

Real-time streaming in practise

Many of our customers can achieve their desired motion capture outcomes during post-process analysis, particularly useful for data clean up and modeling. But there are a vast number of mocap users in other cases or industries that benefit from identifying when correct motions are achieved in real-time. Some examples include (but are not limited to) researching joint functions or the rehabilitation of movement disorders in laboratory settings, where those carrying out this work may need to repeat actions to understand when progress is being made.

Multiple users are aware of BioFeedTrak being a tool to indicate a particular frame where an event occurs – a heel strike for gait analysis, or ball release in a pitching test as some examples – but its function is extensive. BioFeedTrak also gives you the ability to track and measure motions performed by a subject, kitted out with markers, and automate feedback cues to alert the subject to perform that action differently, or continue in the same way until a certain height, distance, or time, for example, is reached.

These cues could be a pop up window, a flashing icon, or a sound, but the BioFeedTrak interface is fairly limitless in providing whatever form of feedback best fits the user or environment. 2D and 3D motion capture can be controlled with immediate effect using real-time feedback, with the added benefit that the BioFeedTrack functionality is available in Cortex.

How BioFeedTrack works

BioFeedTrak can simply be found by following Tools>BioFeedTrak Event Editor:

The BioFeedTrak Event Editor creates events, whereas the BioFeedTrak Event Timeline allows users to assign an event to a frame, or discover on which frame a particular event has occurred:

While movement data gets tracked in Cortex, BioFeedTrak can control how and when your feedback will be shown to the motion capture subject. 

BioFeedTrak Event Editor allows you to provide a description of your feedback, according to the action it is following along with. These “Events” can be enabled in “Live” mode. Imported scripts can then instruct and trigger the program to perform the desired feedback. Using a visual feedback example, a script could indicate that a running subject needs to change direction once they have reached a certain marker in the room, tracked by mocap cameras. 

The “Presentation Graphs” functionality in Cortex also provides a real-time graphical representation of a subject’s movement data within the interface. When linked to the script, the program follows this data so that it knows to provide feedback when numerical touchstones are reached on the graph. BioFeedTrak can also train a motion actor to reach a specific point using a “Threshold Event”, which will apply the desired feedback once a certain event is completed. 

Visual and audio forms of feedback make up the biggest use cases which can be shown to the motion subjects: directional arrows like the example above, or beeping sounds. But as scripts are written by the user, forms of feedback are open-ended to cater to any environment and measure a range of variables. 

Video example: Tracking distance measurement with audio feedback

Here, BioFeedTrak and Presentation Graphs have both been set up and synchronized to adjust a sound’s pitch based on the distance between a thumb and forefinger. The script tracks the measurement between the digits’ mocap markers and provides the pitch adjustment feedback based on that distance. 

Video example: Measuring maximum value with visual feedback

In this video, BioFeedTrack Event is measuring the maximum ground reaction force according to the peak value that is seen during the capture. When greater values are reached, the pop-up message is updated until capture is completed, whereby the remaining value displayed in the popup indicates that topmost ground reaction force. 

Video example: Assessing body weight percentage with visual feedback

In another visual example, the script is written to identify when a certain body weight percentage gets applied onto a plate scale. When the desired force achieves an optimal weight (the “Threshold Event”) the subject gets informed by a pop-up text window changing from red to green. This method is especially useful for rehabilitation practice; in this case, to check weight percentage exerted onto a prosthetic leg.

Giving motion actors the ability to realize a full range of motion with instant feedback is a helpful way for you to improve a range of processes and save time. Using the BioFeedTrak function within Cortex software along with motion capture cameras means that rich data gets collected simultaneously, and feedback is provided instantly in a live setting without the need to send data to a third-party application for similar feedback functions. Whether you need greater real-time feedback for biomechanics research, rehabilitation efforts or workplace training, BioFeedTrak is a handy built-in tool to best streamline your motion capture projects

If you’re a Cortex user and would like to find out more about using BioFeedTrak, chat to our Customer Support team. If you’re exploring mocap solutions and would like to find out more about Cortex, please book a demo.


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