One of the most common things that is said by an audience who has just witnessed spectacular special effects is, “that looked so real!” In fact, a VFX artist is recognised when his work features characters or backgrounds that appear to be real. This does not mean that the featured work must necessarily mimic real life. For example, no one really believes that a purple elephant exists just because they see it on screen. And yet, those very audience are enthralled to see a purple elephant whose skin texture and colour compositing is done by paying great attention to detail. That is when the audience come out of the theater saying,“that looked so real!”http://www.youtube.com/watch?v=Vunk72tZf5Q
A common misconception is that all a VFX artist does is to make objects look real. Besides merely replicating real life, one of the challenges that are overcome by photo real phenomenon is to re-create real life imagery. With the help of the camera’s eyes, objects are brought to life that deviates from the laws of nature outside the screen. For example, if a movie sequence shows a man with a missing arm moving towards the audience, it is easily believable. But the challenge comes when trying to induce a suspension of belief by illustrating a man with a missing head moving toward the audience in a similar manner.
There are two ways to approach the shooting of a photo realistic VFX sequence. It directly depends upon the content of the sequence. If the object in question is something that abides by the laws of nature, say, a dog or a table, the visual effects supervisor will choose to photograph as much of the real thing as possible to get the right texture, compositing and light. This may also involve video shooting a live prop. This is known as photo-realism.http://www.youtube.com/watch?v=luo67oTgSOs
The other way involves featuring objects that do not obey laws of nature. When an object in question is an alien, there isn’t really much to compare. Different people in the production team may have various ideas on how the creature should sound or move. In this case, the director may choose to select an animal that is closest to his vision of the alien. For example, if the director envisions the creature as Medusa then he will probably ask his effects team to show live octopus or snakes in place of the creature’s head.
It is ultimately the VFX artists skill to make every shot as close to the real thing as possible. But integrating VFX characters with their virtual environments is never a sole task. A room full of artists lock their heads to create that show-stopping, photo-realistic VFX sequence.