Approximative Real-time Soft Shadows and Diffuse Reflections in Dynamic Scenes

Information

• Publication Type: Master Thesis
• Workgroup(s)/Project(s):
  • Rendering and Modeling
• Date: October 2007
• First Supervisor: Stefan Jeschke
• Keywords: precomputed radiance transfer, indirect illumination, global illumination

Abstract

This thesis describes a method for approximative soft shadows and diffuse reflections in dynamic scenes, based on a method by Ren et al. [32]. An overview of precomputed radiance transfer and spherical harmonics is also presented, as well as a short introduction to global illumination. The proposed method uses a low-order spherical harmonics basis to represent incident radiance and visibility on the hemisphere of a receiver point. Diffuse reflecting geometry and shadow casting geometry is represented as sets of spheres. The spheres of an object approximate its shape and diffuse surface color as seen from any viewpoint. In a first pass, the direct illumination of an object is projected to its spheres and stored along with an approximation of the diffuse surface color as SH vectors defined over the surface of each sphere. In a second pass, the average color and the visibility for each sphere at a receiver point is found. The product of average color and visibility is used to approximate the incident radiance from diffuse reflections. Using a sphere set approximation instead of actual geometry for both soft shadows and diffuse reflections allows us to compute the visibility and diffuse reflections of an object on the fly at runtime. This text also describes a GPU implementation of the method and discusses obtained results. Interactive performance with relatively smooth framerates of over 20 fps is achieved for moderately complex scenes.

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BibTeX

@mastersthesis{guerrero-2008-dip,
  title =      "Approximative Real-time Soft Shadows and Diffuse Reflections
               in Dynamic Scenes",
  author =     "Paul Guerrero",
  year =       "2007",
  abstract =   "This thesis describes a method for approximative soft
               shadows and diffuse reflections in dynamic scenes, based on
               a method by Ren et al. [32]. An overview of precomputed
               radiance transfer and spherical harmonics is also presented,
               as well as a short introduction to global illumination. The
               proposed method uses a low-order spherical harmonics basis
               to represent incident radiance and visibility on the
               hemisphere of a receiver point. Diffuse reflecting geometry
               and shadow casting geometry is represented as sets of
               spheres. The spheres of an object approximate its shape and
               diffuse surface color as seen from any viewpoint. In a first
               pass, the direct illumination of an object is projected to
               its spheres and stored along with an approximation of the
               diffuse surface color as SH vectors defined over the surface
               of each sphere. In a second pass, the average color and the
               visibility for each sphere at a receiver point is found. The
               product of average color and visibility is used to
               approximate the incident radiance from diffuse reflections.
               Using a sphere set approximation instead of actual geometry
               for both soft shadows and diffuse reflections allows us to
               compute the visibility and diffuse reflections of an object
               on the fly at runtime. This text also describes a GPU
               implementation of the method and discusses obtained results.
               Interactive performance with relatively smooth framerates of
               over 20 fps is achieved for moderately complex scenes.",
  month =      oct,
  address =    "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria",
  school =     "Institute of Computer Graphics and Algorithms, Vienna
               University of Technology ",
  keywords =   "precomputed radiance transfer, indirect illumination, global
               illumination",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2007/guerrero-2008-dip/",
}