Runner can be defined as an Assistant coordinator. Their responsibility is to support all of the members of the company and provide the things that they want. They need to do a variety of jobs. They deliver materials and messages between different departments. They organize meeting and inform people to attend it. Apart from that they also do some little things like locking up, provide tea and coffee to workers.
As I know Runner is an entry-level position. Besides, it is a good way for the people who want to join the VFX industry but without relevant degree education. The reason because that duties of these jobs can help them easy to understand the process of making VFX. It is a straight way for them to acquire knowledge about VFX.
In addition, Runner is an essential part of the VFX industry. It should be involved in every project which can make the programmer more smooth. And also they always need passion and patient for their jobs.
Matchmove artist can be defined as tracking artist. The duties of Matchmover is that to insert the CG scenes into live-action footage with correct position, scale orientation.
They use given information to digitally recreate onset environment. The workflow of matchmove can be broken down into two steps. In the first step, the artist needs to identify and track objects. They should choose several specific points on the objects or images. Then they can get a series of 2D coordinates from the results of calculating these points. The second step is to get the digital camera from these 2D paths through the computer calculating.
The tracking artist can go to the worksite and put the makers on objects. Then they can use these markers to track the camera motion trail and calculate the relevant data in the 3D scene. These data can be used in the next step like composing. They do this by using 3D programmers like Maya or Nuke.
Here is an example of tracking by using Nuke and Maya.
The duty of Roto artist is to create roto mattes and prepare plates for the compositors using various software.
Roto artists trace the areas of live-action frames where the computer graphics will overlay or interact with live images, and allow all the elements of the scene to be layered convincingly. Their jobs can make compositors combine the various elements accurately.
Roto artist normally uses rotoscoping to remove the green screen or other things which are not allowed appearing on the screen.
The workflow of Roto is quite similar to masking in Photoshop. Creating a mask by using curves and adjust it. It is a kind of repetitive work that need artists to be more patient and motivated. The roto artists role exists more often on special effects work, within the facility houses or on projects that combine the live-action and computer graphics.
Here is the example of rotoscoping by using Nuke.