Once all the multi-pass images have been rendered compositors can make an overall improvement to each pass as well as adjust the final composite more artistically. With a full understanding of mathematical formulas of digital compositing and a strong aesthetic
ability, a seamless composite will be created. Advanced
compositing effects can be achieved by using an alpha
channel with a series of math operations. The most
common compositing operation is to combine image A
(foreground) and B (Background) through a number of
math formulas. However, at this stage of combining
multi-passes the main operation formulas are: Over, Plus,
Multiply [12].