| Part II
TV Graphics
and Virtual
Reality Sets
Virtual Reality Sets
 Within the last few years computer-generated graphics have moved into a whole new arena: simulating complete settings. These are referred to as virtual reality sets.
The color of the background that can be used for keying is normally
either green or blue. As shown below, the color can be electronically removed and another
video source inserted (keyed in) to replace it.
In this case a model in
a studio sitting in front of a blue background can be made to appear within
a computer-generated fantasy scene.
Although this is a fantasy scene, very realistic settings can now be computer generated and keyed in behind talent. (Note the computer-generated scene below.)
In the 2007, three-part, SiFi Network production, Tin Man, for example, the elaborate backgrounds were created in a computer and the actors simply acted in front of a solid green background.
On the left a model with a fan in front of her is made to look as if she is bouncing along on a jet-ski in the ocean.
A video recording of the ocean and surrounding scenery taken from the back of a speeding boat is keyed into the green area behind her.
This results in a realistic scene, and the model doesn't even have to get her hair wet!
If it stopped here, the "realism" would be confined to one point of view. But in the real world cameras move and perspectives change. Let's look at an example.
Note the woman standing against the blue background on the right. Now look in the two monitors at the top of the photo and notice that a complete setting has been inserted (keyed into) this live scene.
Although the woman may not be able to actually sit down in the chairs seen in the setting, she can convincing walk behind them and they will pass in front of her body as she moves.
However, she can sit down on the blue box shown behind her in this photo, which, if things are positioned correctly, can make it appear that she is sitting down on one of the virtual reality chairs.
The camera can pan, tilt, and zoom in on her, and the keyed-in
setting will shift appropriately.
This  enlargement of the TV monitor above the woman shows the complete effect in more detail as seen from the camera's position.
Why use virtual reality settings?
A computer can store scores of instantly available backgrounds -- backgrounds that would take thousands of square feet or meters of storage space within a production facility, not to mention thousands of dollars in materials and many hours of construction and setup time.
Matching the Sources
When video sources are combined
into a single scene the effect should be "seamless," that is, the combined result should blend together unnoticed.
Six characteristics of the video sources should be
consistent.
1. The brightness and contrast of the video sources must be the same.
2. The lighting must match, especially
the direction of the lights.
3. The color balance of the video sources must match, especially if skin tones are involved.
4. The sharpness of the video sources should be the same. As a last resort you may have to slightly soften one source so that it will not "stand out" from a companion source.
5. Video sources as well as film have a
subtle but inherent "grain" or "noise" pattern. If one video source is "cleaner" than another, the difference will tip off views that something is amiss, especially in HDTV.
Although it's not a totally desirable solution,
as we've noted, subtle differences can be addressed by slightly degrading one video source with the electronic filters.
6. The relative perspectives must match. This is primarily established by the original lens focal length and camera-to-subject distance.
With a sophisticated photo program such as Photoshop not only
can image perspective be altered but (within limits) video sources can be
matched. |
In the not-to-distant future we'll be talking about totally realistic virtual (computer-generated) actors and on-camera talent. Even today we have realistic looking heroes on the Internet and in films that were born and raised within a computer. No union contracts; no worry about working overtime or on weekends; no personal accommodations or "artistic differences" to contend with; and no 20-million dollar salaries!
Motion Tracking
The little white dots on the male and female subjects in this photo are used in motion tracking.
A video camera tracks the movement of these subjects (actually, the dots) and transfers the data to animated figures in a computer.
The action is normally transferred to an elemental wire frame version of the animated drawings.
Once the action is established, the computer can be used to "flesh out" the drawings to resemble any desired figure.
This process not only greatly simplifies the process of animating figures, but since the white dots represent numerous points of movement, it results in more realistic action.
 All of this was taken a few steps further in the 2007, 3-D film Beowulf, based on the English epic poem, circa  700 A.D.
In this case both the actors and the backgrounds originated in digital electronics.
Real actors such as Angelina Jolie and Anthony Hopkins were used, but they were digitized by motion tracking, altered, and then put into virtual reality sets.
Added to this was a bevy of computer created creatures and monsters that (fortunately) are worse than anything we find in reality.
Virtual reality sets are also easy to change -- no gallons of
paint involved, just a series of mouse clicks.
In the next section we'll introduce a new topic, and one that is central to the medium of television: lighting.
|
