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Tuesday, November 20, 2007

Photo Real and Realism in Visual Effects

At the start of most projects every director requests their shots be photo real

What does Photo Real mean? Are realistic vfx shots a lot more difficult than fantasy shots?

Photo Real means to create a shot that looks as real or true to life as it possibly can. It can mean that the visual effect is so totally convincing that the audience doesn’t see it. Another term for this is Invisible effects.

The lighting, textures, detail and compositing try to mimic a scene that the audience will think is real. To do this the visual effects supervisor shoots as much reference as possible when shooting the plates (live action footage that will be augmented or modified with visual effects). This may mean filmining a physical prop in the same lighting and setup. The clock in The Mask and a piece of fur for Van Helsing were photographed for the TDs (Technical Directors) to use as a look and lighting reference.

As much information is recorded at the time of photography as possible. This includes lighting diagrams, measurements of the set, camera and lens information as well as filming of the chrome and gray spheres.

All the vfx artists that work on the shot will have access to that material and be able to use it directly as well as to use it as a comparison. From this they try to create and integrate the images as much as possible.
The visual effects animator may film or obtain reference footage of people or animals moving to use as a guide, even if it’s a fictional creature.

The trouble is you may not even be creating a shot that will ever be believed.
No matter how well the animator, TD and compositor do their job if the script calls for a pink feathered whale in the sky it still won’t be considered Photo Real by the audience. There’s nothing wrong with creating shots like this since that’s the requirements for the film. The vfx artists try to add as much of real life as they can into shots like this to give it a more solid foundation. This may mean moving the whale slowly and adding in a haze layer to set the scale.

This leads to our second question regarding the difficulty of creating realistic effects.

There’s the impression that realistic effects are very difficult and much harder than shots dealing with fantasy or science fiction. Yes, realistic effects are difficult when you’re trying to create something very complex such as a held close-up of a human, moving cloth or flowing hair. But the difficulties of a shot are usually more dependent on the specific shot and less on the context of the content.

Let’s consider an effects shot: a man on crutches coming toward camera and is missing one leg. The audience will easily accept the man missing part of his leg, especially if it’s an unknown actor. The audience knows this could be real and doesn’t require a suspension of disbelief. Now consider the same shot but instead of missing the leg this man is missing his head. The headless man however doesn’t exist in real life so the audience instantly knows it not real. It will be in the back of their minds no matter how well the vfx are done. A large part of the reality of a shot is based on the perception from the viewer. From a difficulty level these are similar and use the same techniques. The headless man is probably more difficult because you have to create and track the inside of the collar.

Suspension of disbelief plays a large role in film. To some degree everything is a bit unreal in film. The basic story is a fabrication and the dialogue is hand crafted. The director of photography doesn’t necessarily match real life. He lights it to go for a specific style and to make it cinematic. Note that this can be a real problem when you’re trying to match greenscreen people with real outdoor backgrounds). Stunt people rig ramps to make cars spiral in mid-air. Not necessarily real, but certainly visually exciting (cinematic). This is the same thing with the winged spaceships and hearing explosions in the Star Wars films. Not real but cinematic.

Hopefully the story will keep the audience engaged and there will be nothing to force the audience to fixate on the effect. Anytime you give the audience a reason to suspect something, they will find it. You could have a real shot and if the audience thinks something has been added they’ll happily point out several things that are wrong with the shot. A real shot can seem fake under the certain circumstances.

People think since something exists and they know what it looks like they could certainly judge the quality. The reality is most of these effects when correctly deigned pass by audience members unless they’re very poorly done or there’s something to arouse their suspicion.

If you have a matte painting of a stylized or haunted house and center it in frame as the only thing in the shot then it’s going to be suspect. If you add a matte painting of a normal house to fill in a vacant lot on a street and then have the actors in the foreground the audience is unlikely to think about the matte painted house, especially if it doesn’t play a promenant role. Most people think a matte painting has to be super detailed but the primary issue with matte paintings is to get the lighting and perspective right.

The advantage of creating something real is you have reference of the real object or creature to constantly compare to while working on the shot. It may take a lot work to get your CG model or other items to match the real thing but you always know how close your are and where it falls short.

With imaginary shots there are frequently doubts and changes to the design since you don’t have anything to compare to. Some people think the creature should move it’s arms in one way and another group thinks it should move them in a different way. The director may switch his/her thoughts as well. A real reference gives everyone something to lock into.

If you recreate one of the NASA rocket shots now you have reference to the original material and people will accept it. They may know that you created it but it won’t remove them from the movie. If you showed the same footage 50 years ago people wouldn’t accept it as real since they had nothing to relate to.

Old movies had shots done on stage sets that were supposed to be outside. People in cars were placed in front of a rear projection screens. By today’s standards those shots don’t hold up as well because we have a different level of realism in films. It’s not that people at that time thought they were real, it’s that they accepted it much as a theater audience accepts a stage play in front of single sheet sets.

This also applies to camera moves. If you move around a model like a helicopter then the audience will accept it more than if it’s totally static from 1000 feet up or if it moves a mile in 2 seconds. The director may have wanted a photo real effect but in the effort to spice it up by moving the camera faster and further than it could in real life, you destroy the illusion of reality you had created. If you zoom out to space and then back down thousands of miles away like on Google earth then that a style decision but not one that will help the feeling of realism.

The ‘though the engine’ shots in Fast and Furious or the slit-scan shots from 2001 are pure stylized shots. They may have had a high tolerance as to what they looked like but they would still require a fair bit of effort to make work.

Some directors want to try to convince the audience that something is real by focusing on the effect and doing what they can to show it off. In the headless man shot they want the camera to fly around the man and then down through the collar to prove that there’s nothing there. This is like the magician that moves the hoops over the levitated assistant floating over the floor. But the difference is most of the time the visual effects are used to tell the story. By trying to convince the audience the shot may actually come across as more fake.

In summary, the vfx artist tries to make every shot as real as possible. In some cases that may not be possible due to the subject matter itself and in other cases may just be a style choice. Creating invisible effects is usually more dependent on the subject matter and the design of the shot than the execution difficulty.

4 comments:

  1. Hi Scott,

    That's a well reasoned and concise breakdown of the trials and tribulations of effects work, especially the differences between "documentary reality" type films and full-blown fantasy. I've done work on both types, World Trade Center and a couple of Harry Potters for example. For me, the fantasy is always more difficult precisely because you have no reality to compare your work against and because it is so obviously an effect. I've gone into a little more detail about some of these issues, with specific attention to CGI here, if anyone is interested.

    Thanks again.

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  2. Hello Mr Atrocity,

    I'm still sifting through your posting and the original article. (See the link in the post above) Very nice stuff. CG vs Models has been on my list for awhile. Maybe I'll have to do a posting sooner.

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  3. Hi Scott,
    as a vfx artist (FX TD) who is facing the challenges of creating "photoreal" imagery on a daily basis I really loved your thoughts on this matter. One more thing I really think is worth discussing is the fact that even though we try to replicate real-life, photoreal phenomena as we see it; we should always take into account the fact that in the vfx we are looking through the "camera's eyes" which brings in a certain deviation from how our human mind perceives the world and objects in it. I guess what I'm trying to say is that we are in fact re-creating real-life images but looking through the camera lens. Hope this makes sense ;)

    Best regards

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  4. I am not an artist, but think one of my kids can be. I actually never thought of handing over the camera to my kids for contest purpose. They often click photos of nature with intelligent touch. We got some nicer ones from their excursions too.

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