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In a very broad sense the historical development of computer graphics can be considered in three phases, each a giant step down the road towards "realistic" computer generated images. The first, during the late 1960's and early 1970's, can perhaps be characterized as the "wire frame" era. Basically pictures were composed of lines. Considerable em­ phasis was placed on "real time" interactive manipulation of the model. As models became more complex and as raster technology developed, eliminating the hidden lines or hidden surfaces from the image became critical for visual understanding. This requirement resulted in the second phase of computer graphics, the "hidden surface" era, that developed during the 1970's and early 1980's. The names associated with hidden surface algorithms read like a who's who of computer graphics. The cul­ mination of the hidden surface era and the beginning of the current and third era in computer graphics, the "rendering" era, was Turner Whitted's incorporation of a global illumination model into the ray trac­ ing algorithm. Now the goal was not just to generate an image, but to generate a realistic appearing image.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract
Realism is often a primary goal in the creation of computer generated imagery. A key element in realism is displaying the correct colors for the objects in an image. Color is described in Webster’s (Guralnik 1978) as “the sensation resulting from stimulation of the retina of the eye by light waves of certain lengths”. This implies a human perceptual color component, the sensation produced; and a physical color component, the light waves of certain lengths.
Roy Hall

2. The Illumination Process

Abstract
The elements of the illumination process that are useful in computer generated imagery are highly dependent upon the rendering technique that is used. The advancement of image generation techniques is characterized by alternating leaps in illumination models and in rendering technique. Rendering techniques are just now approaching the level of sophistication that requires an accurate energy representation of the illumination of surfaces. The information presented in this chapter will aid in the formulation of new illumination models to meet this challenge.
Roy Hall

3. Perceptual Response

Abstract
The visual system detects, assimilates, and interprets information about our surroundings. The perceptual mechanisms are very complex. The detection apparatus is the eye, which selectively detects different colors of light. Two eyes placed at different locations provide two geometries interpretation, thus allowing the visual system to interpret depth relationships. Image processing in the mechanism enhances edges, motion, color patterns, and spatial textures.
Roy Hall

4. Illumination Models

Abstract
The application of research in physics and optics to computer graphics constitutes an evolution governed by the current visible surface algorithms, by what is considered computationally reasonable, and by the level of realism that is acceptable. The illumination models used in practice differ greatly from the theoretical treatment of Chapter 2. The illumination models used fall into three general classifications: empirical, transitional, and analytical. The shading techniques that evolved with these models fall into three corresponding classifications: incremental, ray tracing, and radiosity methods, Table 4.1. In addition, a hybrid classification has recently emerged that combines the radiosity and ray tracing approaches.
Roy Hall

5. Image Display

Abstract
The display process begins with image information describing the color and intensity at any point on a image plane and is completed by an observer perceiving the resultant displayed image. The steps in getting from the image information to the observed perception involve transforming the image data so it can be displayed within the limitations of the display device. Traditionally, part of the transformation occurs within the rendering step before image files are written and the remainder of the transformation occurs when the image file is mapped into a specific display device.
Roy Hall

Backmatter

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