Issue link: https://digital.copcomm.com/i/18322
By NORIKO KURACHI CG Bridging Something New with Computer Graphics C omputer graphics, like other scientific fields, has made great strides, thanks to landmark developments at various times throughout its history. Established on innovative discoveries made during the 1970s and 1980s, the field of CG was itself something of a revolution. Since its establishment, CG has made steady progress toward producing ever more interesting graphics, created with ever greater efficiency. Computer graphics research is conducted in two realms: academic and industrial. Te academic perspective tends to place priority on new theoretical concepts, while the industrial perspective focuses on apply- ing the theories in production. Tese two perspectives require different creativities, and the progress of CG technologies relies on the collabora- tion between them. Here we examine some of the landmark discoveries made by the interplay of these two branches, as well as take a look at the road to where they might lead. In most cases, revolutionary developments in computer graphics begin with experimental work that attempts, from a physically based point of view, to bridge some new component with graphics. An ex- ample of this is the bridging of photographs and graphics, which later came to be called “image-based” technologies. Computer graphics traditionally needed lengthy computation times in order to produce a high-level photorealistic look that is truly comparable with (and even indistinguishable from) photographs. Te essential idea of image-based technologies is to substitute such computation with photographs by directly using them for image synthesis. Tis approach began with the recovery of 3D geometry and textures of objects from photographs, followed by the recovery of real-world lighting from photographs, as detailed in the paper “Rendering Synthetic Object into Real Scenes: Bridging Traditional and Image-Based Graphics with Global Illumina- tion and High Dynamic Range Photography” by Paul Debevec (SIG- GRAPH 1998). Te basic theories that support image-based modeling and rendering were already popular in other fields of computer science, such as computer vision; however, image-based lighting was the grand, new invention in the field of CG. Tis development was supported by Noriko Kurachi, a former programmer and longtime journalist for the Japanese magazine CGWorld, is about to release her book The Magic of Computer Graphics: Landmarks in Rendering, published by AK Peters, Ltd. The book examines the latest trends in the field of CG rendering, including the topics described in this article. 8 October 2010 Arthur and the Invisibles was Luc Besson’s first CG-animated film; the CG was created by BUF, which pioneered the use of image-based modeling and rendering in entertainment projects. To satisfy Besson’s desire to work with real actors, BUF developed an original performance-capture system that introduced the concept of multiview stereo, which was the beginning of video motion capture. (Top) The performance is captured with video cameras from two different camera angles. (Bottom) The performance that was recovered using the video motion-capture method is applied to a character. an earlier invention called High Dynamic Range Imaging (HDRI). In photographs taken with an ordinary digital camera, the pixel val- ues that exceed a specific threshold are clamped; therefore, the brighter regions of the photographs often fail to represent the physically accurate brightness of the scene. HDRI is a technique that converts ordinary photographs to special photographs in which every pixel value indicates physically accurate brightness. In the converted photographs, each pixel holds exactly the same brightness as that in the real scene. Terefore, in image-based lighting, the pixels of the background plate act as if they were the light sources scattered in the background scene, thereby accu- rately approximating the lighting from the environment. HDRI enabled the use of photographs to synthesize new images—in essence, leading to the true bridging of photographs and computer graphics. Image-based lighting was the breakthrough that really lev- eraged HDRI, and it was followed by other image-based techniques that switched to HDRI to produce a photorealistic look much more efficiently than traditional, physically based rendering methods, which Images courtesy BUF Compagnie.