Refraction in Discrete Ray Tracing
Refraction is an important graphics feature for synthesizing photorealistic images. This paper presents a study on refraction rendering in volume graphics using discrete ray tracing. We describe four basic approaches for determining the relative refractive index at each sampling position, and examine their relative merits. We discuss two types of anomalies associated with some approaches and three different mechanisms for controlling sampling intervals. We apply the refraction rendering to objects with uniform as well as non-uniform optical density, and objects built upon mathematical scalar fields as well as volumetric datasets. In particular, the study shows that the normal estimation plays a critical role in synthesizing aesthetically pleasing images. The paper also includes the results of various tests, and our quantitative and qualitative analysis.
KeywordsScalar Field Interval Length Spatial Object Graphic Scene Volume Dataset
Unable to display preview. Download preview PDF.
- 1.A. Kaufman, D. Cohen and R. Yagel, “Volume Graphics”, IEEE Computer, 26(7), pp. 51–64 (1993).Google Scholar
- 6.L. Westover, ‘Footprint evaluation for volume rendering”, ACM/SIGGRAPH Computer Graphics, 24 (4), pp. 59–64, (1988).Google Scholar
- 8.L. Sobierajski and A. Kaufman, “Volumetric Raytracing”, Proceedings of IEEE Symposium on Volume Visualization, pp. 11–18 (1994).Google Scholar
- 9.N. Stolte and R. Caubet. “Discrete Ray-Tracing of Huge Voxels Spaces”, In Eurographics’95, pages 383–394, Maastricht, August (1995).Google Scholar
- 11.Britannica.com, Snell’s Law, http://www.britannica.com, December 2000.
- 12.M. Born, E. Wolf, Principles of Optics, Pergamon Press, New York, 5th Ed., (1975).Google Scholar
- 13.D. S. Kay, “Transparency for Computer Synthesized Images”, Proc. SIGGRAPH, pp. 158164 (1979).Google Scholar
- 14.T. Whitted, “An Improved Illumination Model for Shaded Display”, Communications of the ACM, pp. 343–349 (1980).Google Scholar
- 16.R. Hall, Illumination and Color in Computer Generated Imagery, Springer-Verlag, New York, (1989).Google Scholar
- 17.R. Satherley and M. W. Jones, “Extending Hypertextures to Non-Geometrically Definable Volume Data”, In Chen, Kaufman, and Yagel (eds), Volume Graphics, pp. 211–225, Springer, 2000.Google Scholar
- 18.S. Treavett and M. Chen, “Pen-and-Ink rendering in volume visualization”, Proc. IEEE Visualization 2000, Salt Lake City, Utah (2000).Google Scholar
- 19.A. Winter and M. Chen, “vlib: a volume graphics API”, submitted to VG01: international Workshop on Volume Graphics, (2001).Google Scholar
- 20.R. Yagel, D. Cohen, A. Kaufman, “Normal Estimation in 3D Discrete Space”, The Visual Computer, pp 278–291 (1992).Google Scholar
- 21.T. Moller, R. Machiraju, K. Mueller, R. Yagel, “A Comparison of Normal Estimation Schemes”, IEEE Proceedings of Visualization 97, pp 19–26 (1997).Google Scholar
- 22.J. D. Foley, A. van Dam, S K. Feiner and J. F. Hughes, Computer Graphics: Principles and Practice, Addison-Wesley, Reading, (1990).Google Scholar