![]() ![]() Shadow mapping projects a special dynamically created texture on scene geometry to calculate shadows. Today, this method is used in a multitude of Hollywood movies that contain computer graphics and special effects. The shadow-mapping algorithm came to computer graphics in 1978 when it was introduced by Lance Williams (Williams 1978). However, the stencil shadows approach has some serious disadvantages: it's heavily dependent on CPU work, it can produce only hard shadows, it uses a large amount of fill rate (which means that even though a GPU may support the technique, it could run poorly), and it cannot be used with hardware-tessellated surfaces. It offers advantages such as the large number of GPUs that support it (the only essential hardware feature is support for an eight-bit stencil buffer), its independence from the type of light source, and the high quality of its generated shadows. The stencil shadows method, which is demonstrated in Doom 3, is used widely by game developers. Two popular methods are available for visualizing shadows in real-time computer graphics: stencil shadows and shadow mapping. With the advent of per-pixel shading, we can produce realistic materials using complex mathematical and physically based models of lighting. The geometry processors in modern GPUs can process millions of primitives per frame, letting us design complex worlds. GPUs now allow us to create images previously available only in professional 3D offline-rendering programs. Figures 12-1 and 12-2 show examples of shadows from our own demo, which is provided on the book's CD and Web site.įigure 12-2 A Close-Up of the Character in Our Demo For example, shadows are a major part of the story line in id Software's Doom 3, one of the most technologically advanced games. In computer games, shadows-along with lighting, music, and special effects-play a very important role in portraying a realistic game atmosphere. In computer-generated scenes, an object's shadow enhances our perception of the object and the relationship between objects. Yet, the appearance of such shadows is one of the most important factors in achieving graphic realism. One of the most difficult problems in real-time computer graphics is generating high-quality shadows. The CD content, including demos and content, is available on the web and for download.Ĭhapter 12. You can purchase a beautifully printed version of this book, and others in the series, at a 30% discount courtesy of InformIT and Addison-Wesley. ![]() GPU Gems GPU Gems is now available, right here, online. ![]()
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