Soft Planar Shadows Using Plateaus

Eric Haines
Autodesk, Inc.

This paper appears in issue Volume 6, Number 1.
Purchase this issue from the akpeters.com web site.

Abstract

This paper presents an algorithm for rapidly creating and rendering soft shadows on a plane. It has the advantages of rapid generation on current hardware, as well as high quality and a realistic feel on a perceptual level. The algorithm renders the soft shadow to a texture. It begins with a hard drop shadow, then uses the object’s silhouette edges to generate penumbrae in a single pass. Though the shadows generated are physically inaccurate, this technique yields penumbrae that are smooth and perceptually convincing.

Author Information

Eric Haines, Autodesk, Inc., 1050 Craft Road, Ithaca, NY 14850 erich@acm.org

Images

The three images below show the results of three ways of generating shadows:

(a) Hard shadows cast onto a plane, applied as a texture

(b) Soft shadows, done in a single pass using the plateaus method described in this paper. (it's a GIF because the JPEG version shows speckling artifacts in some umbrae which are not truly there.)

(c) Physically correct shadows, using Heckbert and Herf's method, 256 passes

BibTeX Entry

@article{Haines01,
  author = "Eric Haines",
  title = "Soft Planar Shadows Using Plateaus",
  journal = "journal of graphics, gpu, and game tools",
  volume = "6",
  number = "1",
  pages = "19-27",
  year = "2001",
}