The areas of live action frames are traced by Roto artists where computer graphics will overlap or interact with live images. Mattes (clear areas) are created inside the frame in order to allow all elements of the scene to be layered convincingly. This helps the Compositors in combining all the various elements accurately.
The most complex shape that the subject is in can be found, to outline that first, to understand the maximum points required to be rotoscoped. Rotoscoping tools used in the compositing software have advanced and deep deviation or curvature that can be controlled to make detailed curved lines with least number of points – image segmentation, creation of mattes or masks, More often than not using rotoscoping. The essential surfaces should be isolated individually. The level of detail depends on the required conversion quality and budget.
In Rotoscopy one can trace an object using a set of tools within the compositing software for making a new alpha channel to a specific part of an image sequence or video. They can manually create this alpha through copying the tracing on top of elements inside the video and create different shapes around the object and provides animation to those shapes to sync with the movement on all the frames. The system automatically interpolates between keyframes to usually provide required result/output without having to create a new frame every time.
This is one of the steps in processing 2D to 3D Conversion movies (the process of transforming 2D film to 3D form). Once mattes/mask have been created through rotoscope it will move to next process called Depth map. It is only through this Depth map that the conversion of 3D form from 2D can be effected.
The use of blue and green screens can make the process of compositing varied elements inside a scene much more simple, (however not every shot can take advantage of blue or green screens) so rotoscoping even now plays a significant role in the entire process of visual effects.This can be a time consuming process, but the results of rotoscoping can be excellent. If more time and effort go into a roto job, the finer the results can be. It is really a very rewarding process! Every movie, TV show or music video that has special effects will require rotoscopy to enhance the picture quality and hence the Roto artists are and will remain an integral part in the VFX pipeline.
NUKE, Mocha, Fusion, Silhouette & AfterEffects are some of the software widely used in rotoscopy for best quality and ease in delivery of output.