question: Why do CGI humans still look unnatural?
comment: It's because we're social animals, trained to pick up on subtle emotional queues in facial movements. Faces are the first things in this world that most of us recognize. And it's mostly subconscious. We've been doing it that long. CGI still fails most of the time to get those motions perfect. Maybe the range of motion is dead on, but the skin doesn't stretch and wrinkle like a real face. Or maybe the skin doesn't have enough texture, or light penetrates the skin a little too deep (or not deep enough), or a myriad of other little things. The point is, this part of the brain that is tuned to watch for these things is seeing all this face stuff and the math isn't adding up. Something is still *off*.
passages: BULLET::::- Human facial proportions and photorealistic texture should only be used together. A photorealistic human texture demands human facial proportions, or the computer generated character can fall into the uncanny valley. Abnormal facial proportions, including those typically used by artists to enhance attractiveness (e.g., larger eyes), can look eerie with a photorealistic human texture. Avoiding a photorealistic texture can permit more leeway.
  
  Section::::Criticism.
  
  A number of criticisms have been raised concerning whether the uncanny valley exists as a unified phenomenon amenable to scientific scrutiny:
   BULLET::::- The 2001 film "", the first photorealistic computer-animated feature film, provoked negative reactions from some viewers due to its near-realistic yet imperfect visual depictions of human characters. "The Guardian" critic Peter Bradshaw stated that while the film's animation is brilliant, the "solemnly realist human faces look shriekingly phoney precisely because they're almost there but not quite". "Rolling Stone" critic Peter Travers wrote of the film, "At first it's fun to watch the characters, […] But then you notice a coldness in the eyes, a mechanical quality in the movements".
   BULLET::::- The 2010 live-action film "" features a computer-generated young version of actor Jeff Bridges (as a young Kevin Flynn and Clu), which reviewers have criticized as creepy. Vic Holtreman of Screen Rant wrote, "Finally we get to the CGI recreation of Jeff Bridges as a young man. Have we finally gotten past the 'uncanny valley' (where the mind/eye discerns that something is just not quite 'real')? Sadly, no. As long as young Kevin Flynn wasn’t talking, the face looked great – but as soon as he spoke, the creepy factor pops up. He looked like he had a face full of Botox […] One could argue that Clu was a computer program and should have been 'stiff' compared to a human, but even in the opening scene of the film where we see the real-world young Kevin Flynn, the same effect is present". Manohla Dargis of "The New York Times" wrote that the appearance of young Kevin was "a simulacrum that here looks like an animated death mask". Amy Biancolli of the "Houston Chronicle" wrote, "Regarding Bridges' digital de-aging: It's creepy. It's a little less creepy on Clu's face (he's not human, anyway) than on Kevin's in a scene from 1989, but on either of them it has the waxen look of storefront mannequins - or over-Botoxed socialites".
   BULLET::::- The 2016 live-action film "Rogue One" features the CGI likenesses of the deceased Peter Cushing and a young Carrie Fisher "reprising" their respective roles of Grand Moff Tarkin and Princess Leia. Graeme McMillan of "The Hollywood Reporter" wrote, "The Tarkin that appears in Rogue One is a mix of CGI and live-action, and it… doesn't work. — In fact, for a special effect that's still stuck in the depths of the uncanny valley, it's surprising just how much of the movie Tarkin appears in, quietly undermining every scene he's in by somehow seeming less real than the various inhuman aliens in the movie." Kelly Lawler of "USA Today" wrote, "the Leia cameo is so jarring as to take the audience completely out of the film at its most emotional moment. Leia’s appearance was meant to help the film end on a hopeful note [...] but instead it ends on a weird and unsettling one".
   A thermal imaging camera was employed for scenes showing "invisible" animals (most notably Isabelle the gorilla) or Sebastian following his transformation and the unsuccessful attempt to restore him to visibility; the same technique was used for characters when they look through thermal goggles. As Isabelle was played in part by a man in a gorilla suit, crew members had to stand by and warm the suit with hair dryers in order for the thermal camera to accurately emulate an actual gorilla's warmth.
   One of the greatest challenges in computer animation has been creating human characters that look and move with the highest degree of realism. Part of the difficulty in making pleasing, realistic human characters is the uncanny valley, the concept where the human audience (up to a point) tends to have an increasingly negative, emotional response as a human replica looks and acts more and more human. Films that have attempted photorealistic human characters, such as "The Polar Express", "Beowulf", and "A Christmas Carol"
  
  have been criticized as "creepy" and "disconcerting".
   BULLET::::- Design elements should match in human realism. A robot may look uncanny when human and nonhuman elements are mixed. For example, both a robot with a synthetic voice or a human being with a human voice have been found to be less eerie than a robot with a human voice or a human being with a synthetic voice. For a robot to give a more positive impression, its degree of human realism in appearance should also match its degree of human realism in behavior. If an animated character looks more human than its movement, this gives a negative impression. Human neuroimaging studies also indicate matching appearance and motion kinematics are important.
   BULLET::::- Some reviewers of the 2009 animated film "A Christmas Carol" criticized its animation as creepy. Joe Neumaier of the "New York Daily News" said of the film, "The motion-capture does no favors to co-stars [Gary] Oldman, Colin Firth and Robin Wright Penn, since, as in 'Polar Express,' the animated eyes never seem to focus. And for all the photorealism, when characters get wiggly-limbed and bouncy as in standard Disney cartoons, it's off-putting". Mary Elizabeth Williams of Salon.com wrote of the film, "In the center of the action is Jim Carrey -- or at least a dead-eyed, doll-like version of Carrey".
   BULLET::::- The 2015 live-action film "Terminator Genisys" contains a scene featuring a computer-generated young version of actor Arnold Schwarzenegger (as a young T-800 Terminator), which some reviewers thought was affected by the uncanny valley. Eric Mungenast of the "East Valley Tribune" wrote of the film, "One notable technological problem stems from the attempt to make old Schwarzenegger look young again with some digital manipulation — it definitely doesn’t cross over the uncanny valley". Writer and reviewer Simon Prior wrote of the film, "Even the 'Synthespian' version of Arnie isn’t as horrific as you might expect, although it’s still clear that CGI hasn’t yet conquered the Uncanny Valley issue". (The film's predecessor, 2009's "Terminator Salvation", also has a scene with a CG young Schwarzenegger that provoked similar reactions from some viewers, but unlike in the newer film, this earlier version does not speak.)
   BULLET::::- In 2003 audience debut of photo realistic human-likenesses in the 2003 films "The Matrix Reloaded" in the burly brawl sequence where up-to-100 Agent Smiths fight Neo and in "The Matrix Revolutions" where at the start of the end showdown Agent Smith's cheekbone gets punched in by Neo leaving the digital look-alike unnaturally unhurt. The Matrix Revolutions bonus DVD documents and depicts the process in some detail and the techniques used, including facial motion capture and limbal motion capture, and projection onto models.
   Human image synthesis
  
  Human image synthesis can be applied to make believable and even photorealistic renditions of human-likenesses, moving or still. This has effectively been the situation since the early 2000s. Many films using computer generated imagery have featured synthetic images of human-like characters digitally composited onto the real or other simulated film material.
  
  Section::::Timeline of human image synthesis.
   BULLET::::- In a review of the 2007 animated film "Beowulf", "New York Times" technology writer David Gallagher wrote that the film failed the uncanny valley test, stating that the film's villain, the monster Grendel, was "only slightly scarier" than the "closeups of our hero Beowulf's face... allowing viewers to admire every hair in his 3-D digital stubble".
   BULLET::::- The 2019 film "The Lion King", a remake of the 1994 film that featured photo-realistic digital animals in place of the earlier film's more traditional animation, divided critics about the effectiveness of its imagery. Ann Hornaday of "The Washington Post" wrote that the images were so realistic that "2019 might best be remembered as the summer we left the Uncanny Valley for good". However, other critics felt that the realism of the animals and setting rendered the scenes where the characters sing and dance disturbing and "weird".
   Standard Poser characters have been extensively used by European and US based documentary production teams to graphically render the human body or virtual actors in digital scenes. Humanoids printed in several science and technology magazines around the US are often Poser rendered and postworked models.
  
  Section::::Library.
   A number of films that use computer-generated imagery to show characters have been described by reviewers as giving a feeling of revulsion or "creepiness" as a result of the characters looking too realistic. Examples include the following:
  
  BULLET::::- According to roboticist Dario Floreano, the baby character Billy in Pixar's groundbreaking 1988 animated short film "Tin Toy" provoked negative audience reactions, which first led the film industry to take the concept of the uncanny valley seriously.
   Due to the complexity of human body functions, emotions and interactions, movies with important roles for fully 3D-animated realistic-looking human characters have been rare. The more realistic a CG character becomes, the more difficult it is to create the nuances and details of a living person, and the greater the likelihood of the character falling into the uncanny valley. Films that have attempted to create realistic-looking humans include "" in 2001, "" in 2005, "The Polar Express" in 2004, "Beowulf" in 2007 and "" in 2009. 
   BULLET::::- The 2011 animated film "Mars Needs Moms" was widely criticized for being creepy and unnatural because of its style of animation. The film was among the biggest box office bombs in history, which may have been due in part to audience revulsion. ("Mars Needs Moms" was produced by Robert Zemeckis's production company, ImageMovers, which had previously produced "The Polar Express", "Beowulf", and "A Christmas Carol".)
   BULLET::::- Violation of human norms. The uncanny valley may "be symptomatic of entities that elicit a model of a human other but do not measure up to it". If an entity looks sufficiently nonhuman, its human characteristics are noticeable, generating empathy. However, if the entity looks almost human, it elicits our model of a human other and its detailed normative expectations. The nonhuman characteristics are noticeable, giving the human viewer a sense of strangeness. In other words, a robot stuck inside the uncanny valley is no longer judged by the standards of a robot doing a passable job at pretending to be human, but is instead judged by the standards of a human doing a terrible job at acting like a normal person. This has been linked to perceptual uncertainty and the theory of predictive coding.
   Section::::Design principles.
  
  A number of design principles have been proposed for avoiding the uncanny valley:
   The early 2000s saw the advent of fully virtual cinematography with its audience debut considered to be in the 2003 films "The Matrix Reloaded" and "The Matrix Revolutions" with its digital look-alikes so convincing that it is often impossible to know if some image is a human imaged with a camera or a digital look-alike shot with a simulation of a camera. The scenes built and imaged within virtual cinematography are the ""Burly brawl"" and the end showdown between Neo and Agent Smith. With conventional cinematographic methods the burly brawl would have been prohibitively time consuming to make with years of compositing required for a scene of few minutes. Also a human actor could not have been used for the end showdown in Matrix Revolutions: Agent Smith's cheekbone gets punched in by Neo leaving the digital look-alike naturally unhurt.
   In Pandemic's 1950s-themed "Destroy All Humans!" video game, the Furon character Crypto, a gray-skinned alien, uses a holographic human disguise to infiltrate suburban United States. "In human form he cannot use weapons but is still able to use his mental powers to hurl objects and hypnotize people into becoming obedient slaves."
  
  Some authors portray the mannerisms of aliens using human disguises as awkward, indicating that the aliens may not feel comfortable in their false skins, for instance Vincent D'Onofrio's portrayal of an alien "Bug" wearing a human suit in "Men In Black".
   BULLET::::- Several reviewers of the 2004 animated film "The Polar Express" called its animation eerie. CNN.com reviewer Paul Clinton wrote, "Those human characters in the film come across as downright... well, creepy. So "The Polar Express" is at best disconcerting, and at worst, a wee bit horrifying". The term "eerie" was used by reviewers Kurt Loder and Manohla Dargis, among others. "Newsday" reviewer John Anderson called the film's characters "creepy" and "dead-eyed", and wrote that "The Polar Express is a zombie train". Animation director Ward Jenkins wrote an online analysis describing how changes to the "Polar Express" characters' appearance, especially to their eyes and eyebrows, could have avoided what he considered a feeling of deadness in their faces.
   BULLET::::- Sorites paradoxes. Stimuli with human and nonhuman traits undermine our sense of human identity by linking qualitatively different categories, human and nonhuman, by a quantitative metric, degree of human likeness.
   BULLET::::- Mortality salience. Viewing an "uncanny" robot elicits an innate fear of death and culturally-supported defenses for coping with death’s inevitability... [P]artially disassembled androids...play on subconscious fears of reduction, replacement, and annihilation: (1) A mechanism with a human façade and a mechanical interior plays on our subconscious fear that we are all just soulless machines. (2) Androids in various states of mutilation, decapitation, or disassembly are reminiscent of a battlefield after a conflict and, as such, serve as a reminder of our mortality. (3) Since most androids are copies of actual people, they are doppelgängers and may elicit a fear of being replaced, on the job, in a relationship, and so on. (4) The jerkiness of an android’s movements could be unsettling because it elicits a fear of losing bodily control."
   BULLET::::- Late 2017 and early 2018 saw the surfacing of the deepfakes controversy where porn videos were doctored utilizing deep machine learning so that the face of the actress was replaced by the software's opinion of what another persons face would look like in the same pose and lighting.
  