Facial Motion Capture

James Buckmaster

Intro

Triple A game developers have a tenancy to push further and further when it comes to making everything realistic. This includes 3D Motion Capture which has now become to main tool when it comes to making realistic and believable human behaviour in games but it didn’t come overnight.

It has been a long process of trying to perfect this technology and to this day it still isn’t perfect - there ares still problems and limitations that still occur. During this presentation I will be going into more detail about this.

The ‘Two Types’

• Modern motion capture systems fall intro two general categories, optical and non optical.

• The majority of systems on market today are marker based, this means that the subject must wearing special reflective or lighted markers in order for the system to work.

• Markerless systems are fewer but are able to identify and track subjects without any suits or markers.

Marker Based Optical Motion Capture Systems

• Marker based has been around for a while, making impacts in the film and gaming industry.

• The system quickly identifies objects and tracks their motion which is very difficult and still in research.

• Markers are either highly reflective balls or else small bright lights that stand out from the background.

• Maker based systems are very expensive and take a lot of time to use - games will have to planned around the equipment and not the other way round.

Problems With Marker Based Systems

• Subjects have to wear special body suits with markers on, precise application of the markers is essential, as the software is estimating the position of the subject.

• One applied correctly the systems must go through a ‘user calibration’ process in order for the system to be able to tell which marker is which, after a while and especially when a scene as a lot of characters in it, the process becomes very long.

• Motion capture teams have to be careful that markers don’t get blocked by other objects or get’s moved as the tracking will be inaccurate.

Markerless Motion Capture

• Professional markerless motion capture systems uses advanced technology in order to track subjects without the need for any special suits or markers.

• Without the aid of markers to provide hints to the image processing software, advanced algorithms are required, especially when the aim is to track motion in real time.

• The only software commercially available today is ‘Organic Motions Open Stage’.

Advantages & Disadvantages To Markerless Systems

• No special suits or markers are required, subjects can simply step into the capture area and begin tracking.

• Game developers can capture more accurate motion capture motion data in less time and for a much lower cost.

• The challenge is implementing accurate tracking algorithms that perform well enough to real time use without the aid of markers to provide hints to the software.

La Noire • LA Noire was the first game to use markerless motion capture - in fact they used a combination of

both.

• The marker based system was used when it came to acting out the scenes with their body, it helped construct the characters movements when picking up objects and other things.

• The markerless system is used specifically for the facial capture side of the game.

• The need for high detail facial motion capture was due to the fact that the LA Noire gameplay is detecting when somebody is lying to you - problems have arisen due to the difficulty of creating this look without any motion capture.

• The markerless system captures an actors actions and gives the game developers the best ever template to go from.

Bibliography

• http://kotaku.com/5714438/the-story-behind-la-noires-creepy-real-faces

• http://www.theguardian.com/technology/gamesblog/2010/dec/16/la-noire-making-of-trailer

• http://www.develop-online.net/tools-and-tech/motion-capture-moving-with-the-times/0117523

• http://boingboing.net/2013/02/05/blooper-reel-from-la-noire-rev.html

• http://en.wikipedia.org/wiki/Computer_facial_animation

• http://en.wikipedia.org/wiki/Facial_motion_capture