Digital look-alike

Digital look-alike is a term used to describe a computer animation or a still image so vivid and realistic looking that it fools the watcher to believe it is a human imaged with a camera.
These things have been around since early 2000s with audience debut generally considered to be in the 2003 films Matrix Reloaded in the burly brawl sequence where up-to-100 Agent Smiths fight Neo and in Matrix Revolutions where at the start of the end showdown Agent Smith's cheekbone gets punched in by Neo leaving the digital look-alike naturally unhurt.
In SIGGRAPH 2000 Debevec et al. presented the last missing piece required to make digital look-alikes, which was adequate and feasible capture and simulation of the bidirectional scattering distribution function (BSDF) over the human body and especially the face. Previous attempts to make digital look-alikes had problems in getting the skin to look natural until year 2000 when the portion of light that enters and exits the skin was taken into account.
After the reflectance field of the human face had been captured it became possible with advanced 3D computer graphics programs it is possible to make digital look-alikes.
Photorealistically modeling, animating, cross-mapping, and rendering of characters so lifelike and realistic that they can be passed off as pictures of human is a very complex task and for a believable result both light reflected from skin (BRDF) and within the skin (a special case of BTDF) which together make up the BSDF. Digital look-alikes may be look-alikes of no-one.
The whole process of making digital look-alikes is very complex and it usually includes capture part and synthesis part.
Following things need to be captured in order to make a digital look-alike
#Geometry may be acquired with a 3D scanner such as an Arius3d or Cyberware scanner, or from photographs and movies with stereo camera or multiple cameras utilising machine vision algorithms.
#Textures from RGBXYZ scanner such as Arius3d or photographs
#Reflectance field captured with a light cage and modeled with an Bidirectional texture function (BTF) which is a collection of BSDFs over the 3 dimensional surface
#Motion capture may be shot with a variety of methods mostly a combination of LIDAR and multi-camera computer stereo vision
Both physics/physiology and image-based modeling techniques are often employed in the synthesis part. Hybrid models employing both approaches have shown best results in realism and ease-of-use. Using displacement mapping plays an important part in getting a realistic result with fine detail of skin such as pores and wrinkles.
Examples of digital look-alikes
:*Leading up to 2003 ESC Entertainment with George Borshukov in lead did the digital look-alikes of Keanu Reeves, Hugo Weaving, Laurence Fishburne and Randall Duk Kim for the 2003 movies Matrix Reloaded and Matrix Revolutions.
:*In 2003 The Animatrix: Final Flight of the Osiris a state-of-the-art want to be digital look-alikes not quite fooling the watcher made by Square Pictures.
::One can observe from the clip "Animatrix: Final Flight of The Osiris" that following things are difficult to do digitally (this is based on an assumption that the animators were aiming for photorealism):
:::#where surfaces meet in contact e.g. lips-meeting-lips, eyes meeting eyelids and eyelids meeting eyelids etc. Collisions of basically any non-rigid objects are difficult to render where they meet.
:::#Additionally classically it is known that hair is difficult to do digitally, some hairstyles more ( open hair ), some less (rigid, non moving hairdo ).
:::#Even an untrained eye notices the algorithms controlling running motion look non-realistic contrasted with the running in the end of this TED talk video made in 2009 looks perfectly natural ).
:::#Skin microstructure with the light scattering off the skin and back-from-the-skin is complex
:*In 2009 Debevec et al. presented a new digital look-alike, made by Image Metrics, this time of actress Emily O'Brien whose reflectance was captured with the USC light stage 5<ref name="Deb09"/>
:* Digital look-alikes of Bruce (a lot of them) are seen running fluently and natural looking at the ending sequence of of this video contrasted to the clunky run in the Animatrix: Final Flight of the Osiris which was state-of-the-art in 2003 if photorealism was the intention of the animators.
:*In 2010 Walt Disney Pictures released a sci-fi sequel entitled Tron: Legacy with a digitally youngened digital look-alike of actor Jeff Bridges playing the antagonist CLU
See:
In this TED talk video at 00:04:59 you can see two clips, one with the real Emily shot with a real camera and one with a digital lookalike of Emily, shot with a simulation of a camera- <u>Which is which is difficult to tell</u>. Bruce Lawmen was scanned using USC light stage 6 and also recorded running there on a treadmill and a many, many digital look-alikes of Bruce are seen running in apparent harmony at the end of the clip.<ref name="Deb09"/>
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