How virtual characters move is a really important part of their realism. A great looking character can end up feeling wrong or even creepy if a movement is not as realistic. One way to create movement for a character is to animate them by hand. That is, define several specific poses, and key movements, and let the algorithm interpolate the rest. This requires artistic skills and can be a tedious process. But we can also directly capture the movement of real people through a set of technologies called motion capture. Motion capture, often called, mocap, is the process of recording the 3D movement of a person, normally an actor, in a way that it can be mapped onto a character. This normally means capturing the skeletal movements. We record the movement of the joints of the body. A single video camera can capture the appearance of a movement, but it isn't enough to capture all of the detail in 3D. We need more complex technologies. The most common motion capture technology is optical motion capture. It uses a large number of cameras set up around the room to capture you from every direction. In most systems, the actors need to wear markers. These are small dots or balls that can easily be detected by the cameras. They're normally made of retroreflective material, which means that when a light shine on them, it shines back in the same direction. It is the same thing that road signs are made of. This means that each camera can shine light, and the light from the marker reflects straight back at it. And it's easy to detect the marker because it's very bright. Each camera will detect a marker from its point of view, and then the mocap software does a very complex calculation to work out where the marker is in 3D space based on all of the camera views. If an actor wears lots of markers all over their body, the 3D marker positions can be used to reconstruct all of their joint rotations, which can then be mapped onto a character. And in order to further increase the accuracy, mocap systems normally use infrared lights. So they're not affected by the lighting in the room. This type of marker-based optical motion capture isn't the only possible technology, some use magnetic markers and markerless systems are becoming more popular. In markerless systems, you don't wear any markers and the joint rotations are calculated directly from the moving body. Most markerless systems also use many cameras but there are some cheaper systems based on for instance, the Microsoft Kinect cameras. Having said that, marker-based systems is still the most reliable and accurate. And also, even the simplest motion capture systems can be difficult to set up and run, which makes them out of reach for beginners. But just because you don't own a motion capture system, doesn't mean that you can't benefit from motion capture. There is now a lot of motion capture data available free or to buy online, including on the Unity Asset Store. So you can use realistic motion capture in your work to create very realistic characters.
