CoverageDetecting Algorithm Based on Sub-Pixel GeometricPrimitives

doi:10.16182/j.issn1004731x.joss.201711018

Abstract

Abstract: A hard shadow anti-aliasing rendering algorithm with sub-pixel accuracywas proposed. The method focused on addressing aliasing artifacts of the shadow map due to the sample density mismatching between light space and camera space. The method extracted geometric primitives from the scene's front view from a light source and storedscene visible triangles with fixed-size and local approximation using conservative rasterization; An algorithm was proposed to detect the covered plurality primitives in one texel based on the texel's vertices, and reconstruct testing depth of shadow ray precisely. The experiment results showed that covered primitives' detection algorithm was able toidentify more than 90% triangles implicated in one texel. This method reduced jagged shadows effectively compared with standard shadow mapping.

Key words: shadow map, hard shadows, sub-pixel, anti-aliasing, primitives

CLC Number:

TP391.1

Li Hua, Yang Huamin, Han Cheng, Zhao Jianping. CoverageDetecting Algorithm Based on Sub-Pixel GeometricPrimitives[J]. Journal of System Simulation, 2017, 29(11): 2723-2731.

References

[1] Whitted T.An improved illumination model for shaded display[C]. Los Angeles, California, USA, Proceedings of International Conference on Computer Graphics and Interactive Techniques, 2005, (4): 343-349.
[2] Crow F C.Shadow algorithms for computer graphics[C]. Los Angeles, California, USA. Proceedings of ACM SIGGRAPH, 1977:242-248.
[3] Williams L. Ca Shadow algorithms for computer graphics ting curved shadows on curved surfaces[C]. Los Angeles, California, USA. Proceedings of the 5th Annual Conference on Computer Graphics and Interactive Techniques, 1978, (12)3:270-274.
[4] Pascal L, Jean-Eudes M, Gaël S.Sub-Pixel Shadow Mapping[C].San Francisco, USA. Proceeding of the 18th Meeting of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, 2014:103-110.
[5] 过洁, 徐晓旸, 潘金贵. 基于阴影图的阴影生成算法研究现状[J]. 计算机辅助设计与图形学学报, 2010, 22(4): 579-591.
Guo J, Xu X Y, Pan JG.Present status of shadow generation algorithms based on shadow maps[J]. Journal of Computer-Aided Design & Computer Graphics, 2010, 22(4): 579-591.
[6] Scherzer D, Wimmer M, Purgathofer W.A Survey of real-time hard shadow mapping methods[J]. Computer Graphics Forum(S1467-8659). Black well publishing Ltd, 2011, 30(1): 169-186.
[7] Eisemann E, Schwarz M, Assarsson U, et al.Real-time shadows[M]. Boca Raton, Florida(S0458-3035). CRC Press, 2011.
[8] Stamminger M, Drettakis G.Perspective shadow maps[C].New York. Proceedings of ACM Transactions on Graphics (TOG). ACM, 2002, 21(3):557-562.
[9] Wimmer M, Scherzer D, Purgathofer W.Light space perspective shadow maps[C]. San Francisco, California. Proceedings of Eurographics Symposium on Rendering, 2004:143-151.
[10] Lauritzen A, Salvi M, Lefohn A.Sample distribution shadow maps[C]. San Francisco, CA. Proceedings of Symposium on Interactive 3D Graphics and Games.ACM, 2011: 97-102.
[11] Fernando R, Fernandez S, Bala K, et al.Adaptive shadow maps[C]. Los Angeles, California, USA. Proceedings of ACM SIGGRAPH, 2001: 387-390.
[12] Lefohn A E, Sengupta S, Owens J D.Resolution-matched shadow maps[J]. ACM Transactions on Graphics (TOG)(S0730-0301), 2007, 26(4): 20.
[13] Zhang F, Sun H Q, Xu L L, et al.Parallel split shadow maps for large-scale virtual environments[C].Hong Kong. Proceedings of the 2006 ACM International Conference on Virtual Reality Continuum and Its Applications, 2006: 311-318.
[14] Aila T, Laine S.Alias-free shadow maps[C]. Norrköping, Sweden. Proceedings of the Fifteenth Eurographics Conference on Rendering Techniques, 2004: 161-166.
[15] Hertel S, Hormann K, Westermann R.A hybrid GPU rendering pipeline for alias-free hard shadows[J]. Eurographics Association, Geneva (S2309-5059), 2009: 59-66.
[16] Jia N X, Luo D N, Zhang Y C.Distorted Shadow mapping[C]. St Andrews, UK. Proceedings of the 19th ACM Symposium on Virtual Reality Software and Technology, 2013: 209-214.
[17] Dou H, Yan Y, Kerzner E, et al.Adaptive depth bias for shadow maps[C]. San Francisco, CA. Proceedings of the 18th meeting of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games. ACM, 2014: 97-102.
[18] Dai Q H, YANG B G, Feng J Q.Reconstructable geometry shadow maps[C]. Redwood City CA. Proceedings of the 2008 Symposium on Interactive 3D Graphics and Games, ACM, 2008:4.
[19] Lloyd B, Tuft D, Yoon S, et al.Warping anad Partitioning for Low Error Shadow Maps[C]. Annecy, Fr. Proceedings of: 215-226.
[20] Hasselgren J, Akenine-Möller T, Ohlsson L.Conservative rasterization[J]. GPU Gems, 2005,2: 677-690.
[21] Timonen V.Line‐Sweep Ambient Obscurance[C] //Computer Graphics Forum. Anaheim, USA. Blackwell Publishing Ltd, 2013, 32(4): 97-105.