Markers
The markers are approximate spheres that have a retroreflective tape on them, that either have a velcro-hook pad that can attach to a velco-hoop material (either on the suit or other material) or they have a solid base that can then be glued or taped to a surface; face markers have no base but work in a similar fashion.
Marker Sizes
The markers currently available are 18mm, 14mm, 4mm and 2mm (the latter two are available by request); the 18mm markers (which are soft and flexible) are used for the body (including hands, head and feet), the 14mm (which are solid) are used for solid objects (such as scene reference objects, but not where contact may be established, e.g. swords), the 4mm and 2mm are used for face and fingers. In essence the larger the marker the easier it is for the camera to detect it, but for more delicate tracking (such as for the face) the smaller markers are more suitable (for either and precision).
Camera View
In terms of the camera view, with a 12.5mm lens, an 18mm marker will appear as approximately 7 to 8 pixels when measured from the camera to the floor centre (~4.4m); a marker at the full distance of the space (i.e. the largest distance, which is ~9m) will appear as 3 pixels. In general, whilst the system is set to accept a marker with less than a pixel in distance (which would be 32m away from the camera), it is preferable to retain 3 pixels across in order to appear as a circle
Similarly, a 2mm marker will appear as only 1 pixel ~3.5m away from the camera; which makes facial motion capture more difficult in such an environment. Therefore, in order to perform facial motion capture, we need to bring the camera closer to the subject.