|Please note that this is a BETA version of the document. All information presented is correct but we are working on improving the details.|
Before camera tracking, we have to discuss the kinds of cameras and the differences between them when talking about virtual productions.
Generally, we talk about two very different cameras:
- Physical Camera
- Virtual Camera
A physical camera is the one (or more) you have in your physical studio.
A virtual camera is the one (or more) you have in your virtual studio. This is an idealized 'pinhole' camera.
The most simple version of Green Screen setups is when it's used with stationary cameras. This means that the entire production is captured through one fixed perspective (or in the case of more cameras, it is captured through multiple fixed perspectives). To put it simply, the position of the cameras, the zoom and the focus values are fixed during production. The other option is to use moving (tracked) cameras. For this to work you will need a tracking device, which can send the positional data of the camera. This data can be used to determine the position of the camera in the virtual environment. This means, when you move your camera in your real studio, you also move the virtual camera in the virtual studio. This way the rendered perspective of the virtual scene will follow the movement of the camera. You can also use a mixed setup using both stationary and moving cameras.
Stationary Camera = Untracked Camera
An untracked camera for virtual production simply means that there is no physical camera movement during the production. It is important to note that this applies not just to the position and rotation of the camera, but also to zoom and focus. So there is no change in the angle, perspective, height, rotation, FOV, etc. of the video provided by the untracked physical camera during the production. However, you can achieve limited camera movements with virtual cameras.
Moving Camera = Tracked Camera
Tracked camera for virtual production means, that there is a change in the physical camera's position, FOV, angle, etc. during the production.
Why is camera tracking necessary?
In order to match the change in the 'view' of the physical camera to the view of the virtual camera, so the virtual studio can be 'moved' according to the physical camera's motion, you need a tracking system's tracking data. This data tells the virtual camera how to show the virtual scene, so it matches the real one.