Shooting and Scene Layouts
Once you've created your models, you're ready to photograph them. In the case of physical miniatures, this means positioning the model in a fixed location or on a movable mount, usually in front of a monochromatic background. The model is photographed, sometimes several times for different lighting or motion “passes.” If multiple models are required for one scene, such as a squad of fighter planes attacking a battleship, each model may be filmed separately, then composited, or pulled together, into one scene with the others, along with any extra passes that were required.
If the entire effects sequence is being created digitally, the process is somewhat different. CGI models are arranged in what is called a
One advantage of digital models is that the visual effects artist has options regarding shooting. Each model can be filmed or
For example, if you're shooting a tractor-exploding sequence and realize the tractor should explode half a second earlier, you'd need to render the entire scene again, which might take hours. But rendering just the tractor, or even simply adjusting the existing explosion in the editing room, may only take a few minutes.
If a digital scene involves movement (as compared to a still image), you'll most likely use a technique called
Of course, this is a highly simplistic example. To make this look at all real would require careful timing and adjustment to the movement curve. If you're just getting started, practice with very simple shapes that render quickly. Once you're confident in your skills, use the final model, but begin with simple test versions such as
It's a good idea to practice with different styles of lighting and even shoot several tests to make sure it matches other footage. Be certain you are happy with the look and the emotional feel of the scene before any final shooting begins.
Another key element that you must consider is lighting. Whether real or digital, proper lighting can mean the difference between an imposing aircraft carrier and a bathtub toy. This is even more important if the effect will be added to existing footage shot on a stage or location.
The final step is to put all the pieces, or
To keep all the layers clearly delineated from each other, each is defined by solid black areas called
Many 3-D software programs can create matte lines for you using
When it comes to using blue screens, the truth is that the background screen doesn't have to be blue. Often it's green, or even orange. The strategy of using a single, vibrant color is to make it easier for the person (or computer) creating the matte to distinguish between what images remain and what needs to be matted out. So the choice of color is determined by the colors used in your scene. For example, if your evil alien has blue skin, you probably want to shoot him in front of a green screen. If the shot involves green grass and a blue sky, then orange might make things easier.
Television newscasts use a low-quality version of this in a process called
Rendering in CGI
Since there's no film camera inside the digital world of your computer, the 3-D software program will provide an object that represents the camera. This can be pointed and moved just like a real camera. There will be settings for focus, zoom, and aperture, as well as special lenses and filters to match anything done in the real world. Once you're satisfied with your scene layout, there are several options for rendering:
Wireframe or animatics let you quickly see the relationship of the objects to each other.
Open GL renders a bit slower, but still fast enough for an easy check of color, shading, and shadows.
Ray-tracing provides the most full realistic results.
As it renders, the computer saves the frames on a hard disk, either as individually numbered files, an image sequence, or a digital film file such as Quicktime or Windows Media. These can be replayed at a higher frame rate (usually the standard of twenty-four or thirty frames per second) to create the illusion of motion.
While ray-tracing results in a better image, it can take from a few seconds to several days for a single frame, depending on the complexity of your scene. That's why it's a good idea to do a test render in wireframe before going on to ray-tracing.
To more accurately portray the way the human eye perceives the behavior of objects on film, the software can add effects like motion blur, lens flare, and depth of field. Rising technology and falling prices have brought quality visual effects within reach of any filmmaker willing to take the time to learn the basics, and to experiment with just how much the finished product can be enhanced by visual effects.
Besides film and camera behavior, natural effects are available on some software systems.