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.Perhaps one day when computers get really fast, we ll see the emer-gence of pure ray tracing with high densities of rays becoming a reality.Radiosity, photon mapping, Monte Carlo accounting, and pure ray trac-ing are some of the techniques employed in global illumination.Usingglobal illumination, the animator accepts a different set of rules than thoseprovided for in traditional or standard lighting.If a scene takes place in anexterior setting, the only global illumination instrument needed would bethe sun (perhaps assisted by a reflecting surface to bounce light into a shad-owed area).If a scene takes place in an interior setting, the only light reallyrequired would be the practical lights in such an interior: lightbulbs inlamps, candles, sunlight through the windows, and so on.Now I hear you asking,  What about skylights? Some programs offerskylight or sky dome lighting options that provide various levels of real-06_200505_Avg_ch06 9/5/03 11:31 AM Page 273Let There Be (Rendered) Light273ism based on global illumination.In these options and in many global illu-mination solutions, the user may be offered the ability to enter the calendardate, time of day, and geographical location, whereby the computer willautomatically calculate the precise position of the sun during the course ofyour animation.In other words, as an animator entering the field in this era, you have thebest of both worlds, considering the techniques and tools of advanced, real-istic lighting are still in their infancy and have a long way to go.Render EnginesAs you know by now, a 3-D animation program consists of both the designfunction and the rendering engine.You design the objects and animations;the rendering engine makes the frames.Obviously, rendering is a highlymathematic function.Early in the development of 3-D animation software, rendering was com-paratively simple and merely translated all the user s specific instructionsto the composed frames.As each software developer competed with othersin the field, continual enhancements were added to each brand.Many ofthese enhancements were made possible by relegating larger and largertasks to the render engine.As noted in Chapter 5,  Objects and Surfaces, vast improvements in sur-face textures have been made possible by advances in the rendering com-ponents of the programs.Realistic fur and hair, for instance, are achievabledue to mathematical algorithms that interpret the user s general com-mands ( I want long, shaggy fur here ) into specific formulae that meticu-lously create each strand with the right length, texture, and weight.Nolonger does the operator have to create an individual two-point polygonreplicated thousands of times and apply similar attributes to each one tocreate a field of grass.The render engine can do that automatically bychoosing an appropriate shader for grass.Similarly, the complexity of lighting is currently migrating from theuser s skilled hands to the rendering engine s domain.Some traditional ani-mators are resisting this trend, preferring to remain in direct control byusing specific lighting instruments, especially when a unique, unusualeffect is required.Many game developers, for instance, are loath to abandontheir Hollywood-inspired lighting tools, but the advance of technology, its06_200505_Avg_ch06 9/5/03 11:31 AM Page 274Chapter 6274ever-improving capabilities, and the pressure of producing good work witha limited budget are driving everyone to accept the rendering engine as anindispensable tool in lighting.Although each of the three rendering programs in this book has its ownrender engines, many animators migrate to plug-in renderers or completelyindependent rendering software.One reason is because each renderer hasits own idiosyncrasies, features, and benefits.Rendering is a highly mathe-matical process that pits accuracy against speed.In order to speed up therendering process, some manufacturers truncate the mathematicalprocesses at a certain point, rounding off results and thereby reducing thetime for calculations to take place.The compromise among speed, accuracy,and the necessity to invent better math processes is what makes one ren-derer behave better than another or produce results that appeal to anima-tors in different ways.In order to provide an adequate discussion on lighting, the available ren-dering engines must be covered, as well as the available traditional lightingtools.As a beginner, you must know how lights are used on a 3-D stage,because a scene will always need to be tweaked, and because the real worldand the animation world often coexist in a film.Maybe you ll one day ani-mate a Monsters, Inc., where the real world is only glimpsed occasionallythrough a wooden door.When the director says,  Can we have a goboed keylight on the wormy thing over there, you re going to have to know what agobo and a key light are, and how to get them into your shot.NewTek s Screamer NetNewTek was one of the first companies to address the necessity of render-ing animation over a network of different computers.Originally, they intro-duced ScreamerNet as a separate software product dedicated to renderingLightWave files, but they quickly realized the marketing advantage ofincluding the render software as part of the whole program package [ Pobierz całość w formacie PDF ]