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Psychophysical Experimentation in Computer Graphics

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Dr. Ann McNamara, Trinity College Dublin

  • Computer Science Seminar
When Fri, Jan 31, 2003
from 04:10 PM to 05:00 PM
Where RH 316
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Abstract: Increased application of computer graphics in areas which demand high levels of realism has made it necessary to examine the manner in which images are evaluated and validated. In this talk, we explore the need for including the human observer in any process which attempts to quantify the level of realism achieved by the computer graphics process, from measurement to display.We introduce a framework for measuring the perceptual equivalence (from a lightness perception point of view) between a real scene and a computer simulation of the same scene. Because this framework is based on psychophysical experiments, results are produced through study of vision from a human vision, rather than a machine vision, point of view. This framework can then be used to evaluate, validate and compare rendering techniques. Data gathered through such experimentation can also be used to accelerate computer graphics algorithms. There may be little point spending time or resources to compute detail in an image that would not be detected by a human observer. By eliminating any computation spent on calculating image features which lie below the threshold of visibility, computation times can be shortened - leading to more efficient processing. We are now working to develop experiments that detect threshold visual differences between images and their real world counterpart, and ultimately aim to use these results to direct graphics algorithms to work on those parts of an image that are in most need of refinement., without sacrificing visual quality.This talk will give a detailed description of the construction of an experimental framework that enables human observers to perform the light matching task in real scenes and computer generated representations. Task performance in each case (real versus graphic) can then be compared to give a measure of perceptual equivalence. To illustrate key concepts and results, a case study, involving comparing a test environment, consisting of a small room containing several objects, to its graphical counterpart, will be discussed.There will be a reception in RH 114 from 3:50 until 4:10.

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