Ray Traced Shadows: Maintaining Real-Time Frame Rates

Jakub Boksansky, Michael Wimmer, Jiří Bittner
Ray Traced Shadows: Maintaining Real-Time Frame Rates
In Ray Tracing Gems: High-Quality and Real-Time Rendering with DXR and Other APIs, pages 159-182, March 2019

Information

  • Publication Type: Article in a Book
  • Workgroup(s)/Project(s):
  • Date: March 2019
  • Address: New York
  • Booktitle: Ray Tracing Gems: High-Quality and Real-Time Rendering with DXR and Other APIs
  • DOI: 10.1007/978-1-4842-4427-2_13
  • Editor: Erik Haines and Tomas Akenine-Möller
  • ISBN: 978-1-4842-4426-5
  • Open Access: yes
  • Pages (from): 159
  • Pages (to): 182
  • Publisher: Springer

Abstract

Efficient and accurate shadow computation is a long-standing problem in computer graphics. In real-time applications, shadows have traditionally been computed using the rasterization-based pipeline. With recent advances of graphics hardware, it is now possible to use ray tracing in real-time applications, making ray traced shadows a viable alternative to rasterization. While ray traced shadows avoid many problems inherent in rasterized shadows, tracing every shadow ray independently can become a bottleneck if the number of required rays rises, e.g., for high-resolution rendering, for scenes with multiple lights, or for area lights. Therefore, the computation should focus on image regions where shadows actually appear, in particular on the shadow boundaries.

We present a practical method for ray traced shadows in real-time applications. Our method uses the standard rasterization pipeline for resolving primary-ray visibility and ray tracing for resolving visibility of light sources. We propose an adaptive sampling algorithm for shadow rays combined with an adaptive shadowfiltering method. These two techniques allow computing high-quality shadows with a limited number of shadow rays per pixel. We evaluated our method using a recent real-time ray tracing API (DirectX Raytracing) and compare the results with shadow mapping using cascaded shadow maps.

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BibTeX

@incollection{BOKSANSKY-2019-RTS,
  title =      "Ray Traced Shadows: Maintaining Real-Time Frame Rates",
  author =     "Jakub Boksansky and Michael Wimmer and Ji\v{r}\'{i} Bittner",
  year =       "2019",
  abstract =   "Efficient and accurate shadow computation is a long-standing
               problem in computer graphics. In real-time applications,
               shadows have traditionally been computed using the
               rasterization-based pipeline. With recent advances of
               graphics hardware, it is now possible to use ray tracing in
               real-time applications, making ray traced shadows a viable
               alternative to rasterization. While ray traced shadows avoid
               many problems inherent in rasterized shadows, tracing every
               shadow ray independently can become a bottleneck if the
               number of required rays rises, e.g., for high-resolution
               rendering, for scenes with multiple lights, or for area
               lights. Therefore, the computation should focus on image
               regions where shadows actually appear, in particular on the
               shadow boundaries.  We present a practical method for ray
               traced shadows in real-time applications. Our method uses
               the standard rasterization pipeline for resolving
               primary-ray visibility and ray tracing for resolving
               visibility of light sources. We propose an adaptive sampling
               algorithm for shadow rays combined with an adaptive
               shadowfiltering method. These two techniques allow computing
               high-quality shadows with a limited number of shadow rays
               per pixel. We evaluated our method using a recent real-time
               ray tracing API (DirectX Raytracing) and compare the results
               with shadow mapping using cascaded shadow maps.",
  month =      mar,
  address =    "New York",
  booktitle =  "Ray Tracing Gems: High-Quality and Real-Time Rendering with
               DXR and Other APIs",
  doi =        "10.1007/978-1-4842-4427-2_13",
  editor =     "Erik Haines and Tomas Akenine-M\"{o}ller",
  isbn =       "978-1-4842-4426-5",
  publisher =  "Springer",
  URL =        "/research/publications/2019/BOKSANSKY-2019-RTS/",
}