Cameras and Perspective

The camera's positioning can imply certain characteristics or traits about the subject. The camera can be close to or far from the subject. It could be under the subject looking up or above the subject looking down. In addition, cameras both real and virtual have a field of view or, as it's called in Maya, angle of view. That means the camera can be wide-angle or telephoto. The viewer's perception is the intensity of the perspective effect; that is, as the camera views a wider field, the perspective becomes more exaggerated. Normal human vision applied to a typical viewing plane (TV, movie screen) uses a roughly 50-degree viewing angle. Larger angle values view a wider area and produce a stronger, more exaggerated perspective effect, and vice versa, as shown in Figure 1.8.

Figure 1.8. Angle of view and apparent perspective: On the left is a 20-degree angle of view, and on the right, an 85-degree angle of view.

Angle of View and Perspective

Relative height can imply importance. For example, if you want your subjects to look mighty, you photograph them from underneath, as though looking up at a giant statue. To create a lonely or isolated effect, you can photograph the subject from above at some distance.

Perspective implies drama and action. You might have noticed that sleek cars and planes are sometimes photographed from the front at an extremely wide angle quite close to the vehicle body. This gives a wildly exaggerated perspective, as though the vehicle is coming right at you. Telephoto views at a low angle value diminish perspective until the objects in view are so flattened that it's hard to tell which objects are closer. The lack of perspective tends to give a sterile, "schematic view" look to your scene.

Perspective can also impart a sense of scale. Because 3D worlds have no reference point for size, sometimes it's difficult to communicate whether you're looking at a toy car, a normal full-sized car, or a giant car. There are many cues to size, such as the intensity and size of details in a surface (for a car, scratches, metallic flake, and dirt). Using a wider angle lens is an easy way to impart scale quickly, however. Be careful not to overdo it; generally, angles should range from 25 to 80 degrees. For closeups, you're usually better off with a narrower angle on a camera that's farther away because putting a standard or wide-angle camera very close to an object always results in exaggerated perspective, as shown in Figures 1.8 and 1.9.

Figure 1.9. The same subject, but different camera positions and angles of view.

Vanishing Points and Perspective

Renaissance-era artists began to realize the key to realistic landscape painting when they discovered the vanishing point. An image can have one, two, or three vanishing points, depending on the camera's orientation. If the camera is perfectly level, only a single vanishing point is apparent. If the camera is rotated left or right (the camera in Figure 1.10 was rotated left), you get a second vanishing point. If the camera is then rotated up or down, a third vanishing point is introduced.

Figure 1.10. Using 1-, 2-, and 3-point perspective.

In some cases, you might need to position the camera in a place that forces 2-point perspective, but you want only one vanishing point. This often happens in architectural images, when you don't want the buildings to appear to converge at the top, but do want to render the building from a low floor looking up. The way to solve this problem in Maya is to adjust a camera attribute called film offset.

Directing 101

Having learned about camera placement from a still photographer's point of view, now add the dimension of time. Objects can move and change shape or color over time, and the camera can move around the scene. You can also edit several sequences together with cuts or dissolves between different camera passes. At this point, you are in the realm of the movie director. Film direction has some rules that are good to know for shooting 3D action.

Cutting and the "Line of Action"

Generally, when starting a scene, the viewer needs a frame of reference. Directors usually provide it with what's called a master shot, a brief shot of the majority of the setting to give an idea of the layout.

If characters will interact, the master shot usually begins with the two shot, a view of both characters that establishes their relative positions. If a single character is moving around, the full-body shot is referred to as a wide shot. A medium shot shows a character from waist to head. The closeup includes the neck to the top of the head, but the extreme closeup crops from above the eyes to below the lips. These descriptions apply to humans, of course; an alien character's body and facial parts might be in quite different places! At least you have a starting point to describe the shot sequence for telling your story, though.

note

The line of action refers to maintaining the camera on one side of the scene to avoid disorienting the viewer. As in a stage play, where the audience is fixed on one side of the action, it is easy to confuse the viewer if the camera crosses the line of action between the characters, as shown in an establishing shot. For example, if two characters are conversing, the camera stays on one side of an imaginary line between the characters as it cuts between the characters' closeups (see Figure 1.11). The establishing two-shot usually defines which side of the line of action the camera will work from.

Figure 1.11. An illustration of the "line of action."

Scene Motion

A problem that animators of all kinds have is imparting mass and momentum to characters. In life, objects and people rarely start or stop moving instantly, but when they do stop abruptly, things attached to them often wobble or fall off. None of this happens automatically in animation, however, so you must remember the dynamics of real-life motion and simulate it with the motions you create. In cartoons, this motion is often exaggerated: A character's height and width vary radically as it walks, or it spreads out and loses height when hitting the ground.

Center of gravity is also important. For example, if a character rears back, it puts a leg out as a counterbalance; otherwise, it would fall over. Animators often act out their characters' motions and film them for reference to remember these subtle but important facets of real-world movement.

Camera Motion

The camera can move as well, and in a 3D program, there are no limitations it can fly through keyholes, move as fast as a jet and stop instantly, or rotate in place at 100 spins per second. Unless you want your human audience to become upset or ill, however, you should adhere to the same principles as real-life camera operators. If you rotate in place, you must move very slowly, for example. Don't roll (tilt) the camera in relation to the horizon unless you are doing a special effect, such as a fighter jet or roller coaster point of view.

As an animator, you should give the camera mass so that it doesn't start or stop "on a dime." The camera should go from fixed to moving or rotating with gradual acceleration, and go from moving or rotating back to a fixed position with gradual deceleration. You can put the camera on a path, a curvy line that passes through your scene like a roller-coaster rail. Be careful not to lock the camera to the path direction, however, or the result will be a whiplash experience for your viewers. Instead, you usually leave the camera rotation free so that you can animate the virtual viewpoint to move to the natural points of interest, rotating smoothly between them as the camera travels.