COMPUTER ANIMATION at LAWERENCE LIVERMORE LABORATORY S.R. Levine Lawrence Livermore Laboratory Color Print Film Can Be Used Inst

COMPUTER ANIMATION AT LAWERENCE LIVERMORE LABORATORY S.R. Levine Lawrence Livermore Laboratory In any discipline where the desired results of color print film can expended effort can be used instead of high be pictorial in nature, we speed Ektachrome used in most direct find computer graphics. In those color film particular recorders (described below). There are color cases where the results can be displayed as a print sequence films that have a resolution in excess of pictures so as to give the illusion of 200 line pairs/mm of motion, we find computer in any color. That contrasts animation. The sharply with the 20-50 line pairs/mm obtainable uses of animation made by any discipline are with high as varied speed Ektachrome. This becomes important as the disciplines themselves. when we recognize the At the Lawrence fact that a high quality Livermore Laboratory, we film recorder is capable of imaging have been producing computer animated over 150 films for line pairs/mm on 16mm film. Thus, it is clear well over 10 years. These films have been used both that the indirect approach can potentially as a means to aid researchers with their produce a far work and as a means superior product. to communicate to others A second point is the results of their calculations. that during the optical reduction, it is possible to use the printer Until a few years ago, the only means of for special direct computer effects that are not easily programmed. film output was 35mm black and For example, fades and dissolves white microfilm. This film was can be added either viewed for essentially no additional effort. A far directly on a 35mm projector or else reduced better to control over color can be expected. If 16mm on an in-house optical printer. The the user is unhappy use of 35mm proved unsatisfactory with the choice of colors, for the obvious the film can be reprinted with different colors. reason that 35mm projectors are not commonplace This like 16mm involves no additional computer runs. projectors. Whereas we actually have There is one special a 35mm projector at LLL, effect we have used it was recognized that at Livermore on a number of occasions that most other laboratories that we exchange film provides a result with will that is not easily accomplished not have a 35mm projector. by programming. As a simple The 16mm motion picture example, consider film is the most two distorted grids that overlay one another. reasonable medium in which to exchange film Let in the one to be in front colored red and the the scientific community. The main reason one to be in back is the abundance of colored green. Suppose further 16mm motion picture film that these grids move with respect projectors. Also recognize the to one another. fact that there At all those points that the grids cross the is a single standard for 16mm film. It is this film will standard show yellow (red + green = yellow). that allows computer animated films This array of yellow to enjoy the popularity dots gives an undesirable they do. effect that can distract from the information The production of color computer generated the programmer was film is a simple trying to convey. It is, extension to the optical re- in effect, a type of optical noise. duction process. The user produces a number To eliminate of 35mm black this effect by programming and white films each correspond- means computing all of the intersections ing to the particular color desired. of These the two grids, breaking the green lines into films are then superimposed one upon another onto segments with the proper spaces left for the 16mm color film with the appropriate red lines. This is color filter inserted a very time-consuming process into the light path. and not a trivial one to be done This technique is currently the efficiently. most popular A far simpler solution is to first make method for the production of scientific computer a negative animation. copy of the black and white film The major drawback is the time that is to be colored red. required to make the film. We call this a negative The users generally mask. This film is clear except for the black expect to see their results soon after running lines. Now their program. the film to be colored red is printed It is for this reason that onto color film with the red computer films are more often filter. After used to show the color film is backed up in the printer, final results rather than as an alternative the film to be to other forms colored green is printed through of computer output. the negative red mask. This These are however, a few is accomplished advantages to by loading both films into the optical printer production of film in this manner. The quality with the mask of the finished closest to the color print film. product is better than by any The black lines from the negative other technique. This is red mask because high resolution prevent light from passing through the "green" 81 film at exactly those places where the two cross. If we choose to avoid the drift by changing Thus, the red lines will be unbroken and appear the filter for each element as required, then in front of the green lines. Since the negative the time to generate a frame becomes excessive. red mask was made from the original film to be The second system used by film recorders colored red, there is no registration problem. consists of movable arms attached to rotary These techniques are used by Hollywood to insert solenoids or stepping motors. These arms are a scene into a different background. arranged so that more than one filter at a time We also use our optical printer for the pro- can be inserted into the optical path. This duction of color stereo movies. The printer is allows the use of subtractive color. The advantage used to place the images side by side as required here is that seven colors (white, red, green, by the Bolex stereo system we use at LLL. It blue, yellow, cyan, magenta) can be produced is clear that the calculation of the stereo without the need for multiple exposures. For pair is only a time-consuming extension to the pictures that contain a collection of colored calculation of a single perspective view. The lines and characters, this can be a timesaving optical reduction is no more difficult then device. We have found that five or six colors the 35mm to 16mm reduction. The lack of popular- is generally sufficient for most of our work. ity of color stereo movies in the scientific The loss in resolution due to more than one community is not because of the lack of interest filter in the optical path is more than made in such film nor the ability to produce them, up for by the poor resolution inherent in high but rather because of the great difficulty of speed Ektachrome. showing them. Given that we can produce the film, The major advantage of the direct color there is the problem of a special lens for recording systems is one of fast turn around projection, poloroid glasses for viewing on a time. After the film is recorded and processed, special type screen that is probably not available. the user has a color film. Even with our in-house In addition there is not a standard for a 16mm optical printer, a color film is at least 24 stereo format. hours away (more typical is one week). The quick The advantages are not all on the side of turn around time means color film can be used the optical printing method. A number of instal- as another form of output and for many users, lations employ a film recorder with direct color this far outweighs the advantage of added quality recording capability. The essential differences obtainable by the indirect procedure. are in the CRT phospor, lenses, and use of a There is, on the horizon, a new technique filter changer. that promises us the best of both worlds. The The white phospor CRT is usually a P4, P24, technique is direct color recording using lasers. P48 or other braod band phosphor. What is impor- The laser has enough light output to directly tant is that the CRT be capable of emitting expose slow speed high resolution color print relatively equal amounts of red, green and blue film. Use of HeNe, Argon, HeCd give red, green light. The lens must be corrected for this and blue light sources eliminating the need for light. Most high quality black and white film filters. Lasers can be focused down to spot recorders employ a P11 phospor and use a lens sizes less than 1 micron. This compares to a corrected for the blue light this phosphor minimum of 20 microns on a white phospor CRT emits. and can provide all the resolution the color There are two systems for generation of print film can handle. color film. The first is called additive color The color laser film recorder is in some and is generally implemented with a filter changer sense, a far simpler device than the color that consists of a single disk containing at CRT film recorder. The three laser beams are least a red, green and blue filter. passed through intensity modulators and folded It is clear that any color can be generated into a single optical path. Using the modulators, by the proper combination of red, green and blue the three lasers can produce a light beam of light.

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