Correctly and accurately combining normal maps in 3D engines

Abstract

Realistic CGI humans have been the “holy grail” of character artists since the inception of three dimensional (3D) modelling. While 3D characters have become extremely convincing in still imagery, the same cannot be said of animation where realism remains far more elusive. The problem lies in the subtleties in the movement of skin over bone, muscles tensing and relaxing and skin in general stretching, wrinkling and deforming. While some high demand solutions have been found in the film industry, technology limitation does not yet allow these methods to be implemented into games. This research examined how through the use of animated normal maps a low demand solution can be implemented in both film and games animation.

While modelling, texturing and rendering have shown great leaps towards realism, poor facial animation often lets down 3D characters. Films such as Beowulf (2007) are generally criticised as lacking in soul. While individual still frames can be highly realistic, it is in animated sequences where the characters are exposed as unconvincing. A notable exception is the character in The Curious Case of Benjamin Button (2008).

The hypothesis of the paper asserts that the realism achieved in films like The Curious Case of Benjamin Button, through advanced and costly methods employed to capture the subtleties of facial movement, can be approximated by a system of animated texture channels with particular focus on normal maps. This realism can be achieved by procedurally merging animated details and shifting between predefined states that correspond to basic facial expressions, while retaining high detail dermal characteristics and anomalies such as wrinkles, pores, lines, spots and freckles.

This chapter shows how the methods currently employed to combine normal maps within 3D software and 3D games engines are inaccurate or produce undesirable results. This research examines a range of methods currently available and explains the reasons they fail. The chapter concludes with an original solution for combining a theoretically unlimited number of normal maps both accurately and without losing detail or aesthetic value.