Creative Chronicles: Motion Capture

Creative Chronicles: Motion Capture

24 August 2018

Creative Chronicles brings together key insights, information and statistics from the experts at Creative Assembly. We hope this will inspire students and those considering a career in game development.

This edition of Creative Chronicles focuses on Motion Capture.

Motion capture, or Mo-cap, has the ability to add realism of movement to your game characters, picking up detailed nuances that wouldn’t otherwise be possible in the animation process.

 


 

THE UK’S MOST PROMISING DIGITAL SKILL

There is no direct career path into motion capture, but it is intrinsically linked to animation in game development. In fact, careers in animation are increasingly looking for understanding or experience of the motion capture process.

A recent study identified animation as the most promising digital skill for the future UK workforce. Between 2004 and 2012 the UK saw a 53% increase in the number of animation professionals, with over 4,600 people currently working in animation.

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HOW DOES MOTION CAPTURE WORK?

Mo-cap is the process of capturing real movement and mapping it on to a 3D model. It originates from the animation technique rotoscoping, which was first developed in 1915.

History of Motion Capture

The process referred to here is one type of motion capture; Optical-Passive technology. This is the most accurate and common form of mo-cap. Reflective markers are placed around the body, especially in areas of mobility such as the joints. These markers are attached to a special motion capture suit which is worn by the actor.

Infrared lights from cameras placed around the environment reflect off the markers on the body. As the actor moves the infrared lights send data back to the computer via specialised cameras, calculating where these joints are in space. The specialist team interpret this by linking the data together, as a 3D model of the actor.

Then it's a case of building the character over the top of this skeleton or layering in an existing character model – such as an Orc from Total War: WARHAMMER. This has huge application in the games industry, both in-game and in cinematics such as marketing materials.

Mo-cap gives immediate and real time results, reducing the overall cost of key frame-based animation. This real time benefit allows trialing different styles, different movements, different weighted objects or props. The amount of animation data that can be produced within a given time is very large when compared to traditional animation techniques – reducing both cost and meeting production deadlines.

From a cinematic perspective: pre-vis, and the ability to shoot trailers in live action helps to establish camera narrative, continuity, and building the appeal of the characters performance.

 


 

THE PERFORMANCE

A quality mo-cap result for your animators relies a lot on the direction of the shoot. You need to get the right actor to put on a good performance, and this may well be one of your enthusiastic animators with no previous acting experience.

An animator may also be directing the shoot and they need to go in knowing what they want out of it, how they want the actor to behave and the specific motions that are required.

This director has a crucial role in understanding, relaying and getting everyone on set to work to the overall vision – all within resource and budget.

Working out scales, scene compositions and prop interactions are all part of the preparation process to ensure the performance matches the artistic requirements. The director must know the story and history of the main characters’ goals and motives to ensure the character personality and appeal are accurate. This is especially important when the character is historical or comes with a complex lore that fans know before seeing it in-game or watching the cut-scene, trailer or movie.

Mo-cap is only as good as the performance, it needs to be convincing and appealing on the character in-game. But it also needs to be logical and fit with the timeline, the era, the lore and the wider context of the game. To create this emotive and immersive performance, often multiple takes are required to get the complex character interactions right – with speed of motion and strength of motion consistent across all these shots to avoid continuity errors.

 


 

The basics of mocap

THE ROLE OF THE ANIMATOR

There are additional benefits for having the animator or artist commissioning the mo-cap involved in the shoot direction on the day. They know the game and the technical limitations that may arise later in production. They also have the required understanding of motion in weight, continuity, timing and general character motives to provide an artistic eye and feedback to the performance.

Essentially, the animator can be that bridge between the recording and the animation work, reducing the risk of re-shoots or trouble shooting directly in Maya later in production. 

During the shoot there can often be a lot of people, and management of this is key. Everyone needs to know what their role is, and direction needs to be incredibly clear. Mo-cap can be expensive, especially if you don’t have your own setup, so you need to use that time effectively.

The mo-cap process involves specialist technicians as well as the animators, shoot directors and actors. Often these roles overlap. Technicians will oversee all aspects of mo-cap including camera calibration, actor setup, data capture, data cleaning and exporting in the appropriate format for the animators, while also researching and implementing new technologies as required such as VR possibilities, Facial Capture and Virtual Cameras. They will also support animators in directing shoots, using their expert knowledge to advise on movements and working with talent to create the best base for animations.

 


 

MOTION CAPTURE AT CREATIVE ASSEMBLY

Creative Assembly has been involved in the mo-cap process for over 20 years and is one of only a handful of European developers to have an inhouse studio. This gives us a tailored process for quick and accurate turnaround of data and the additional ability to utilise the studio for pre-viz work within our cinematics and animation teams.

Our very first mo-cap set-up consisted of renting a local school gym over the holidays to capture as much data as we possibly could. Now we have our own system and secure working space, with permanent technicians on site, which means we can have someone in a suit and ready to go within half an hour.

Our animators and mo-cap technicians place a huge importance on producing realistic animations. Collaboration and communication are key to this, utilising the studio’s talented people to create and share artistic vision down to the smaller details, such as the weight of the props used. If we add the subtle nuances of swinging a heavy weapon as opposed to a light one, we create a better flow of movement and more accurate data to work with.

 


 

THE TECH

Our motion capture suite encompasses forty eight 16 Megapixel, passive optical infrared cameras across a 120 square metre dedicated studio space.

The system incorporates new hardware from Vicon, using their top of the range cameras, the Vantage System. This has allowed us to increase our volume size (the space in which the actors perform) and gives us improved and more accurate results. With a quicker and more streamlined pipeline, we have the ability to track data more effectively for live streaming and can more efficiently pick up any errors during the shoot.

This software works intelligently when ‘cleaning-up’ the data (the process of looking through the marker data for any gaps due to occlusion). We can also create our own scripts using the internal language of the software, including Python scripting, allowing us to automate additional aspects of the workflow.

RESOURCES

  • Motion Capture Manager, Pete Clapperton, lays out the benefits of an in-house mo-cap studio in this MCV article.
     

  • Back in 2013 we invited PC Gamer into our mo-cap studio to look at the capture behind Total War: ROME II in this video.