With previs as one of the hot topics in visual effects these days, Christopher Harz inspects its roots in animation and gaming.
Previsualization is used as a planning tool, as seen here in the previs (left) and the finished images from Panic Room. All Panic Room images © Columbia Pictures. Courtesy of Softimage|XSI.
Keyframe helped X-Men save on time and money with previs. © 20th Century Fox. All rights reserved. Courtesy of Keyframe Digital Prods. Inc.
You hear a lot about previsualization these days; its also called previs or previz. There are even highly visible specialists in the field, called previsualization supervisors, a job category that did not even exist a few years ago. What exactly is previs, and how does it relate to animation and gaming?
What it is?
A little history is in order to illustrate the basic functions of previs. Long ago (and far away), classic animation started the formal process that led to previs, because animation directors, unlike their live film counterparts, did not have actors that could walk through a scene to try different ideas before shooting began. Perhaps the first rudiments of it were the story scripts generated for Steamboat Willie, which combined key staging sketches with detailed typewritten instructions. These were the predecessors to the storyboard, which Walt Disney developed for planning all of his animated films; they quickly became a standard tool for live-action features as well.
With the dawn of digital animation and gaming came animatics. These are not to be confused with rough draft post-production VFX scenes by the time these are generated, the film is typically in the can. Modern previsualization is a planning tool for the film itself, before a particular sequence is shot, says Ron Frankel, a previsualization supervisor on major films such as Panic Room and Minority Report. It starts out with 3D storyboards, which are then animated. The sets created in previs are very exact replicas of the film production environment, including the limits of the stage, used to help the director design the film and tell the story in a particular way. After the sets are built, rough computer versions of the actors are created and inserted into the scenes.
Pixel Liberation Front (www.thefront.com), which did the previs sequences for both films, used Softimage|XSI to create the sets and virtual actors. Creating the sequences involved extraordinary coordination between all of the parties involved in the film. We worked very tightly with the production designers, the set builders, the director and art director, adds Frankel. We even got involved with the grips. In one scene in Minority Report, with the spiders in the tenement, the camera shot would normally have mandated a custom-made motion control rig. The bids for such a rig were astronomical. Instead, we worked with the grips by running through previs sequences with different camera angles and found a way to track it with a regular crane. The grips practiced using the previs sequences, and nailed everything in one day of live shooting.
Show Me the Money
Although previsualization is not cheap the costs can range from $10K-$20K for a simple shot to more than $500,000 for an entire feature, the benefits of using previs nowadays have tremendous leverage, considering the costs of a major studio film. The rule of thumb is that a typical Hollywood film costs $100,000 a day to shoot, which means that an hour of discussion on the set to clear up confusion can cost more than $10,000. A major mistake being suddenly unable to shoot a scene because a section of the set or a 20-foot crane is necessary but unavailable can easily cost several days of shooting, not to mention frazzled nerves.
The savings caused by previs doesnt end with smoothly planned camera operation, but extends to the building of the set itself. When we were working on X-Men, the production crew was in the process of building a very expensive 40-foot stone wall and a huge bluescreen, says Darren Cranford, the founder of Keyframe (www.keyframe.ca), the first Canadian company that specialized in previs (their credits include X-Men, Driven, Exit Wounds and Bulletproof Monk). But by creating the exact camera view looking out of a jail cell we noted that most of the wall and the area behind it were not visible on camera, so we were able to save a huge amount of construction. We use a mesh of five-foot squares as overlay on each scene, so we can tell exactly what size the practical (physically constructed) set really has to be.
Previs is also useful for budgeting VFX shots, as seen here in X-Men 2. TM & © 2003 20th Century Fox. Courtesy of Keyframe Digital Prods. Inc.
Another fiscal use of previs is for budgeting VFX shots. For instance, if a producer from X-Men had gone to an FX house and said, Give me a quick quote for a shot of Sir Ian McKellen walking through a giant chasm on metal plates with all kinds of things flying around and with a waterfall in the background, they would either ask him, Are you crazy? or give him some huge quote, notes Cranford. Instead, the producer was able to take a previs shot with all the elements laid out, including camera angles, and get a reasonable quote in a reasonable amount of time.
This film is a cross between Red October and
Cranford notes that the demands for modern previs are very exacting. These are not very crude animatics scenes, he says. Theyre more like the high-res cinematics of a video game. One scene can easily have half a million polys in it, complete with 3D sets, detailed backgrounds and multiple moving vehicles and actors. This explains why previs is such a recent occurrence 10 years ago, the 3D animation tools and computer power for quick creation and fast rendering of detailed scenes simply did not exist. On the positive side, it means that previs scenes are actually clean enough that they can be used to pitch the movie to the studio in the first place. A crew had been working for some time to build a set to take test shots for K-19: The Widowmaker, but it was very time consuming, he notes. We created a complete 3D model of the submarine in about two weeks, and inserted characters who walked through the entire virtual set. The resulting scenes were good enough that the producer used them to pitch the studio, and that got it greenlighted. Using previs scenes to pitch a studio is no longer unusual even a megaproject such as The Lord of the Rings trilogy used previs scenes extensively to get its $300 million budget approved by New Line Cinema. This gives you an idea of how much of a film can be affected by previs from the initial funding through pre-production through filming, and finally leading into post-production VFX and DAM (digital asset management). The tie-ins with asset management are especially important for films such as the Matrix franchise, where digital assets from the first film are re-used both for sequels and for gaming spinoffs.
A skilled previs supervisor must be both technician and artist it is the ability of the previs to convey both the movement and feel of the story that enables it to be a critical common portal for the many communities of practice that work on a film including the director and AD, the designers, the set builders, the actors, the producers, the grips, even the musicians creating the score, all of which would normally have a hard time reading from the same page. The extensive use of previs in a film means that the previs supervisor and his animation production team will spend a lot of time with a film. For X-Men, we spent over seven months on the film, and created hundreds of shots and over 45 minutes of 3D animation, remarks Cranford.
What if we moved it just a little
A major role of previs is precise virtual camera placement, and this is one area where directors will brook no compromise. If the director says, I want to put a camera with a 22mm lens one foot from the wall and 10 feet up in the air, thats exactly what we have to give him, notes Cranford. And if he then wants to do what-if explorations, such as, What if we made it a 50mm lens? we have to provide him with that look, and soon. Directors are people who like instant gratification. It can get very exacting for the movie Driven we had to build a virtual racetrack with stands and 14 cameras, and change any and all of the cameras and lenses on a given day.
Cranford relies on 3ds max for enabling him to build precise 3D sets and set up virtual cameras with lenses that are exactly correct. For moving characters and vehicles around, he likes the easy-to-use features of the Character Studio plug-in for max. I use max extensively, along with combustion, which is a great compositing tool. What we typically do first is create the set, using data from the films technical survey group, which hopefully includes blueprints of buildings and rooms and terrain features and elevations. Sometimes we have to go out to the location ourselves, with measuring tools. We take lots of digital photos, which we then use as textured wallpaper for the 3D sets. We also have to pay special attention to light sources.
After we have the basic shots worked out with the producer, we then go on location, taking our laptops. Changes are made on the fly. The director may ask us to mover the characters around several ways on the virtual set fortunately, Character Studio captures all mouse movements and translates them into animations, which we then render and save on-site, turning off features such as smoothing shaders to save time, We use Wi-Fi connections to send our shots back home for more detailed rendering on our render farm in our company. Finally, we output each previs shot to VHS tape or a DVD for the director, so that he has a permanent record to look at.
Using Gaming Technology
The exacting nature of previs for films explains why other than for specific rough sequences of a few films gaming engines have not been used extensively for previs. We even use 3ds max for creating cinematic sequences for videogames, says Tim Miller, creative director of Blur Studios (www.blur.com), which has specialized in creative cinematics for major games. Right now, the virtual cameras in most game engines are not accurate enough for our production demands, and we need much more precise control of the characters. Cranford agrees. Films tend to be extremely procedurally driven, he notes. A director will ask us to move a character five feet to the left, or make a precise camera move. Game engines dont really allow that, and they dont permit the extensive character interaction that we need. Frankel notes that, In the future, I think we may do previs with game controllers and let the director try more hands-on realtime explorations, but the game engines are not there yet.
One type of movie that has used game engines to move characters around though with compromises in resolution and detail are the machinima-type films, which are referenced on the associations Website, www.machinima.com, which also lists upcoming film festivals for such movies. For these short films, not only the previs, but the entire movie, is created with a game engine such as Doom or Unreal. An example of such a short film that can be viewed online is Ozymandias, by Strange Co., which is posted on its website, www.strangecompany.com.
Whats coming up down the road for previs? I expect a much expanded use of previs the trend is that no major movie will be made without it, and its being used more extensively within each movie, which means the demand for animators talented in this area will rise, says Cranford, Initially, some directors resisted the use of 3D because they were afraid that, Someone with a computer will tell me what to do. They now realize that previs supervisors are artists, too, and that they are dedicated to doing whatever the director really needs, to make him feel confident when he starts shooting. And confidence and greatly enhanced creativity within budget is what previsualization is really all about.
Christopher Harz is a program and business development executive for new media enterprises, working with digital animation companies around the world. He writes extensively for trade magazines on topics including the New Internet, visual effects for films and television, online videogames and wireless media. Harz was previously vp of marketing and production at Hollyworlds, producing 3D Websites and videogames for films such as Spawn, The 5th Element, Titanic and Lost in Space, and for TV shows such as Xena, Warrior Princess. At Perceptronics, as svp of marketing and program development, Harz helped build the first massive-scale online animated game worlds, including production of the $240 million 3D animation virtual world, SIMNET. He also worked on combat robots and war gaming at the Rand Corp., the American military think tank.