Compositing and Synchronisation

CGI compositing is an extremely important area of specialization which is required in order to reach the highest level of realism for films utilising special effects.

What is it?
Compositing is the process of combining multiple scenes (usually a virtual component with a real life scene) in a realistic manner, creating an output which looks just as realistic as the original scene without noticeable flaws (de-synchronization of location, colour, movement)

Green/Blue screen compositing - also known as keying, the process involves a character or object you wish to composite into another scene and a single colour background. The colour to use for a background should not be naturally occurring or found anywhere on the object or character you wish to composite. This concept is simple an works on the basis that the software you are using will register the background colour as transparent, allowing only the foreground object to be visible and showing the scene you want in the background. There are many many more variables involved in getting a realistic combination, for example the lighting and atmosphere need to be the same for both scenes and the background colour needs to be solid.

There are other and new ways for compositing, one of which just involves using a camera and software to detect only the moving components in a scene, making the rest of the scene transparent. Static Background Keying, as i like to call it, is usually not solely used for major films and comes as standard with some webcams.


Camera Tracking - I came to be aware of how useful this attribute can be for super-realistic compositing after seeing some compositions by 1st Ave Machine, an animation studio in NYC.


Using camera tracking, the animators can create models within a virtual scene where the computer is aware of the movements the camera took whilst recording footage, this means that once the 3D animation is finished, the rendered output will move according to every movement the camera took, canceling out any de-synchronization. Combined with HDRI texture mapping the final product can look completely life like.

Compositing is used in many, many films, the technique can be used to transform environments and allow the wealthy film companies to create almost anything they want.

I have recently got into Adobe After Effects, for one of my films I'll be trying to composite some of my 3D models into a film project I have been working on, "the false narrator".
Heres a video of the original model, with green screen:



And here's a the final scene where i have keyed out the background and overlaid the original image, with extra effects like blur, noise, colour channel mixing and exposure mapped to sound intensity: