Motion Capture

Motion capture, also known as mocap or motion tracking, is the process of recording human movement and transforming it into digital data. This data can be used in various applications such as animation, biomechanics research, healthcare, sports performance, ergonomic assessment, and more. Motion capture breathes life into digital characters, provides valuable insights into human movement, and allows for the development of innovative training and rehabilitation programs.

Capturing motion involves several steps. Firstly, the subject is prepared for the capture session. This may involve attaching markers or sensors to the subject's body, ensuring they are properly calibrated, and setting up the mocap stage with cameras or other equipment.

Once the subject is prepared, the capture session begins. The subject performs the desired movements, which is recorded by the motion capture system. The system captures the position and orientation of the markers or sensors in real-time, creating a stream of movement data. Different motion capture technologies use different ways to record movement. 

After the capture session, the movement data is processed and cleaned up using dedicated software. This involves removing noise or errors in the data and refining the captured movements.

The cleaned-up motion data can then be used in various applications. It can be used to animate characters in video games, create motion sequences for movies, analyze and improve sports performance, make ergonomic assessments, and much more.

Motion capture has emerged as a transformative technology for many industries. It has changed how we analyze, create, and interact with movement. From immersive animations in blockbuster films to the intricacies of human movement, motion capture data unlocks a world of possibilities. 

Take a look at some of the key applications of motion capture. 

Inertial motion capture offers a distinct set of advantages over optical motion capture, making it an indispensable tool in various applications. Here's a breakdown of its key benefits:

• Freedom of movement: Unlike optical systems with markers and studio constraints, inertial mocap allows for complete freedom of movement in any location. While some inertial mocap systems may struggle with accuracy in environments with magnetic interference, Xsens offers complete magnetic immunity, ensuring high-quality data capture regardless of the environment - on-set, in the lab, in the studio, at the workplace, or on the field, everywhere.

• Portability and ease of use: Inertial mocap systems are compact, lightweight, and user-friendly. They can be set up quickly, making them ideal for on-location shoots, field research or clinical assessments. Inertial motion capture also eliminates the need for cumbersome markers. This simplifies setup, reduces preparation time, and potentially enhances the acting experience by allowing for more natural movement, which translates into character authenticity in the final animation. 

• Exceptional accuracy: Xsens mocap’s advanced sensor fusion algorithms and meticulous calibration processes deliver exceptional data accuracy for most applications. Xsens provides HD reprocessed, production-ready data that requires minimal cleanup. Due to the nature of inertial motion capture, there is no absolute positioning, although it’s close with minimal drift. Absolute positioning can be achieved by adding compatible 3D position-aiding technology.

• Instantly available for use: Having an inertial mocap suit instantly available is a significant advantage. Setting up an optical or markerless shoot takes time and personnel, whereas Xsens can be ready in about 15 minutes. This allows for spontaneous use without the need for extensive preparation. 

• Cost-effectiveness: Compared to traditional optical systems, inertial mocap offers a more cost-effective solution. The elimination of studio setup costs and the ease of use contribute to a lower overall investment. With top of the line motion capture systems such as Xsens that provide production-ready data, the total cost of ownership is even lower as you save time valuable time in post production. 

There are three main types of motion capture systems: optical, inertial, and markerless (AI). Each offers unique advantages and considerations:

Inertial Motion Capture

Inertial mocap utilizes sensors placed on different parts of the body. These sensors are equipped with accelerometers, gyroscopes, and magnetometers, that measure orientation, acceleration and magnetic field interaction. Software then processes this data and reconstructs the movement in 3D space. Xsens is one of the most trusted inertial motion capture technologies, renowned for its exceptional accuracy, ease of use, and robust data processing. Xsens systems are ideal for capturing complex movements in real-world environments.

Pros

• Offers freedom of movement compared to optical systems.

• Portable and suitable for capturing motion in various locations.

• No need for markers, simplifying setup and enhancing the acting experience.

Cons

• Due to lack of absolute positioning, drift can occur over time. Xsens overcomes drift with advanced algorithms. 

• Susceptible to distortion from magnetic fields. However, Xsens mocap offers full magnetic immunity and can be used in any environment. 

Optical Motion Capture

Optical mocap employs multiple high-speed cameras strategically placed in a controlled studio environment. Cameras track reflective markers attached to the actor's body. Software then analyzes the marker positions in each frame, reconstructing the 3D movement data.

Pros

• High accuracy, particularly for detailed movements like facial expressions.

• Established technology with a long track record.

Cons

• Requires a dedicated and controlled environment with specific lighting conditions to avoid marker occlusion.

• Can restrict actor movement due to marker placement limitations.

• Setup and calibration can be time-consuming.

• Requires technical knowledge and multi-person team to operate.

• Expensive and not ideal for multi-actor scenes with close-contact movements.

Markerless or AI Motion Capture

This emerging technology utilizes computer vision and machine learning algorithms to analyze video footage and reconstruct 3D movement data without requiring markers or sensors on the actor.

Pros

• Least intrusive approach, offering maximum freedom of movement.

• Lower setup costs compared to other methods.

Cons

• Accuracy can be lower compared to optical and inertial systems, particularly for complex movements or in challenging lighting conditions.

• Requires a setup with cameras or phones.

• Still under development, with ongoing improvements in accuracy and robustness.