By Rob Harvey
Owner/ Creative Director
Lola Post Production Ltd.
Back in the day (well, the early ‘90s) a few of us at Cell Animation began to use what has become known as previs to plot complex motion control moves and eventually drive the cameras themselves. I can’t honestly remember what we called it but it certainly wasn’t ‘previs’, or ‘postvis’ for that matter. They were probably ‘CG animatics.’ We went on to use the process to produce CG previs of entire commercials, including the non-VFX shots. We called them ‘posh animatics.’ They were so useful on set — an editor could cut a rough assembly as it was shot, replacing the Amstrad-like graphics with the live action on the fly.
The faster and more interactive the software packages have become over the years, the more feasible it is to use ever more complex and polished previs on set. VFX has become so complex over the last decade, and certain types of film are so reliant upon VFX to tell their story that often it isn’t even possible for the filmmakers themselves to know if a given sequence is working or not until they have seen it fully fleshed out in previs/postvis form. Depending on the proposed sophistication of the final effects, these occasionally need to be executed to an incredibly high standard — high enough to have been considered finished effects in years gone by.
Sometimes previs is used to sell the idea of a particular sequence or type of effect to the studios, so again, it needs to be good enough to give a clear indication of how their money will be spent and how spectacular the finished thing will look.
It used to be a running joke on almost every project: You’d provide the production company with a quote for the VFX work required on their latest blockbuster docu-drama about volcano-tsunamis in space, and their first question was always, “Can we see what the finished effects will look like?” How we laughed. But really that’s what previs/postvis has become — a way to allow execs and directors alike to see what they’re going to get before it’s been done, and in doing so, has become a very useful tool for planning and budgeting the finished effects.
Previs is carried out for lots of reasons. Sometimes it’s done simply to inform about composition or timings, to aid the DP with camera heights and lens angles, or an editor with roughing out a first cut. These can be pretty basic. Other times they need to spell out in torturous detail how a series of complicated effects will help tie a whole sequence together, or indeed make up most of the sequence itself. It would have been very difficult for anyone to judge how Gravity was coming along with only faces floating around on greenscreen to look at!
At Lola, we use previs on the majority of our projects. It’s become a part of the pipeline. We’re currently working on a previs that requires hundreds of ships at sea — in a raging gale. The results look like a finished shot, complete with CG waves, avatars on the decks, lightning, even rain on the lens. It needs to cut into the body of the film seamlessly and not jar, so the finish needs to be that bit more polished.
We use the same packages to create the pre-vis as we do for the finished work: Houdini, Maya, even trusty Softimage on occasion, and we might take a look at a games engine or two in the coming months.