Incident Light Metering in Computer Graphics

Information

• Publication Type: Technical Report
• Workgroup(s)/Project(s): not specified
• Date: April 1997
• Number: TR-186-2-97-11
• Keywords: color mapping, global illumination, tone mapping

Abstract

Every rendering process consists of two steps. The first is the computing of luminance values by methods like ray tracing or radiosity, and the second step is the mapping of the computed values to values appropriate for displaying. In the last years, as alternative to simple linear scaling which maps the average value to the medium lumninance, some new ways of mapping were introduced. These new methods are based on photography analogies and on human vision models. All existing methods follow, implicitly or explicitly, the reflected light metering principle. The method introduced in this paper is the first that follows the incident light metering used in professional photography and in the movie industry. Actually the irradiances are measured using a set of diffusors, which are placed automatically in the scene, and a linear scale factor based on these measurements is used to map the computed radiances to the display device. The diffusors act as half space integrators, they collect the light energy from all half space directions. The light comes from the primary light sources, or it is the result of various interreflections. The newly introduced method reproduces original colors faithfully even for scenes with very low or very high average reflectivity.Every rendering process consists of two steps. The first is the computing of luminance values by methods like ray tracing or radiosity, and the second step is the mapping of the computed values to values appropriate for displaying. In the last years, as alternative to simple linear scaling which maps the average value to the medium lumninance, some new ways of mapping were introduced. These new methods are based on photography analogies and on human vision models. All existing methods follow, implicitly or explicitly, the reflected light metering principle. The method introduced in this paper is the first that follows the incident light metering used in professional photography and in the movie industry. Actually the irradiances are measured using a set of diffusors, which are placed automatically in the scene, and a linear scale factor based on these measurements is used to map the computed radiances to the display device. The diffusors act as half space integrators, they collect the light energy from all half space directions. The light comes from the primary light sources, or it is the result of various interreflections. The newly introduced method reproduces original colors faithfully even for scenes with very low or very high average reflectivity.

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BibTeX

@techreport{Kresimir-1997-ILMCG,
  title =      "Incident Light Metering in Computer Graphics",
  author =     "Kresimir Matkovic and L\'{a}szl\'{o} Neumann and Attila
               Neumann and Werner Purgathofer",
  year =       "1997",
  abstract =   "Every rendering process consists of two steps. The first is
               the computing of luminance values by methods like ray
               tracing or radiosity, and the second step is the mapping of
               the computed values to values appropriate for displaying. In
               the last years, as alternative to simple linear scaling
               which maps the average value to the medium lumninance, some
               new ways of mapping were introduced. These new methods are
               based on photography analogies and on human vision models.
               All existing methods follow, implicitly or explicitly, the
               reflected light metering principle. The method introduced in
               this paper is the first that follows the incident light
               metering used in professional photography and in the movie
               industry. Actually the irradiances are measured using a set
               of diffusors, which are placed automatically in the scene,
               and a linear scale factor based on these measurements is
               used to map the computed radiances to the display device.
               The diffusors act as half space integrators, they collect
               the light energy from all half space directions. The light
               comes from the primary light sources, or it is the result of
               various interreflections. The newly introduced method
               reproduces original colors faithfully even for scenes with
               very low or very high average reflectivity.Every rendering
               process consists of two steps. The first is the computing of
               luminance values by methods like ray tracing or radiosity,
               and the second step is the mapping of the computed values to
               values appropriate for displaying. In the last years, as
               alternative to simple linear scaling which maps the average
               value to the medium lumninance, some new ways of mapping
               were introduced. These new methods are based on photography
               analogies and on human vision models. All existing methods
               follow, implicitly or explicitly, the reflected light
               metering principle. The method introduced in this paper is
               the first that follows the incident light metering used in
               professional photography and in the movie industry. Actually
               the irradiances are measured using a set of diffusors, which
               are placed automatically in the scene, and a linear scale
               factor based on these measurements is used to map the
               computed radiances to the display device. The diffusors act
               as half space integrators, they collect the light energy
               from all half space directions. The light comes from the
               primary light sources, or it is the result of various
               interreflections. The newly introduced method reproduces
               original colors faithfully even for scenes with very low or
               very high average reflectivity.",
  month =      apr,
  number =     "TR-186-2-97-11",
  address =    "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria",
  institution = "Institute of Computer Graphics and Algorithms, Vienna
               University of Technology ",
  note =       "human contact: technical-report@cg.tuwien.ac.at",
  keywords =   "color mapping, global illumination, tone mapping",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/1997/Kresimir-1997-ILMCG/",
}