Generalized linear perspective shadow map reparameterization

ABSTRACT

Shadow mapping is an efficient approach for real-time shadow rendering, but it usually suffers from inherent aliasing artifacts due to the image-based nature. The aliasing errors of shadow mapping can be classified into two categories: perspective aliasing errors and projection aliasing errors. In this paper, we present the Generalized Linear Perspective Reparameterization (GLPR) of shadow maps to reduce perspective aliasing errors. The generalized perspective reparameterization function is formulized first, in which three parameters are taken into account: 1) the cross angle between the view and light direction, 2) the distance from the projection reference point to the near plane in the perspective warping frustum, and 3) the pixel's depth. The distribution of perspective aliasing errors of all currently existing perspective reparamterizations can be uniformly described by this function. Based on this generalized representation, the direction-dependent warping transform is chosen to keep the linear perspective aliasing distribution when the light direction is not perpendicular with the view direction.

REFERENCES

• 1: Jukka Arvo, Tiled Shadow Maps, Proceedings of the Computer Graphics International (CGI'04), p.240-247, June 16-19, 2004 [doi>10.1109/CGI.2004.97]
• 2: Chong, H. Y., and Gortler, S. J. 2004. A lixel for every pixel. In the Eurographics Symposium on Rendering 2004, Eurographics, Eurographics Association.
• 3: Franklin C. Crow, Shadow algorithms for computer graphics, Proceedings of the 4th annual conference on Computer graphics and interactive techniques, p.242-248, July 20-22, 1977, San Jose, California
• 4: Randima Fernando , Sebastian Fernandez , Kavita Bala , Donald P. Greenberg, Adaptive shadow maps, Proceedings of the 28th annual conference on Computer graphics and interactive techniques, p.387-390, August 2001 [doi>10.1145/383259.383302]
• 5: Naga K. Govindaraju , Brandon Lloyd , Sung-Eui Yoon , Avneesh Sud , Dinesh Manocha, Interactive shadow generation in complex environments, ACM Transactions on Graphics (TOG), v.22 n.3, July 2003
• 6: Kozlov, S. 2004. Perspective shadow maps: care and feeding. GPU Gems, Addison-Wesley.
• 7: Low, K.-L., and Ilie, A. 2003. Computing a view frustum to maximize an object's image area. J. Graph. Tools 8, 1, 3--15.
• 8: Martin, T., and Tan, T.-S. 2004. Anti-aliasing and continuity with trapezoidal shadow maps. In the Eurographics Symposium on Rendering 2004, Eurographics, Eurographics Association.
• 9: William T. Reeves , David H. Salesin , Robert L. Cook, Rendering antialiased shadows with depth maps, Proceedings of the 14th annual conference on Computer graphics and interactive techniques, p.283-291, August 1987
• 10: Pradeep Sen , Mike Cammarano , Pat Hanrahan, Shadow silhouette maps, ACM Transactions on Graphics (TOG), v.22 n.3, July 2003
• 11: Marc Stamminger , George Drettakis, Perspective shadow maps, Proceedings of the 29th annual conference on Computer graphics and interactive techniques, July 23-26, 2002, San Antonio, Texas
• 12: Lance Williams, Casting curved shadows on curved surfaces, Proceedings of the 5th annual conference on Computer graphics and interactive techniques, p.270-274, August 23-25, 1978
• 13: Wimmer, M., Scherzer, D., and Purgathofer, W. 2004. Light space perspective shadow maps. In the Eurographics Symposium on Rendering 2004, Eurographics, Eurographics Association.
• 14: Andrew Woo , Pierre Poulin , Alain Fournier, A Survey of Shadow Algorithms, IEEE Computer Graphics and Applications, v.10 n.6, p.13-32, November 1990 [doi>10.1109/38.62693]

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism
          Subjects: Color, shading, shadowing, and texture

Keywords:
real-time rendering, shadow algorithms