Fast Phong shading

ABSTRACT

Computer image generation systems often represent curved surfaces as a mesh of planar polygons that are shaded to restore a smooth appearance. Phong shading is a well known algorithm for producing a realistic shading but it has not been used by real-time systems because of the 3 additions, 1 division, and 1 square-root required per pixel for its evaluation. We describe a new formulation for Phong shading that reduces the amount of computation per pixel to only 2 additions for simple Lambertian reflection and 5 additions and 1 memory reference for Phong's complete reflection model. We also show how to extend our method to compute the specular component with the eye at a finite distance from the scene rather than at infinity as is usually assumed. The method can be implemented in hardware for real-time applications or in software to speed image generation for almost any system.

REFERENCES

• 1: Tom Duff, Smoothly shaded renderings of polyhedral objects on raster displays, ACM SIGGRAPH Computer Graphics, v.13 n.2, p.270-275, August 1979
• 2: James D. Foley , Andries Van Dam, Fundamentals of interactive computer graphics, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1982
• 3: Gouraud, H. June 1971. "Continuous Shading of Curved Surfaces," IEEE Transactions on Computers, vol. 20, no. 6, pp. 623-628.
• 4: William M. Newman , Robert F. Sproull, Principles of interactive computer graphics (2nd ed.), McGraw-Hill, Inc., New York, NY, 1979
• 5: Bui Tuong Phong, Illumination for computer-generated images., 1973
• 6: T. Whitted , D. M. Weimer, A Software Testbed for the Development of 3D Raster Graphics Systems, ACM Transactions on Graphics (TOG), v.1 n.1, p.43-58, Jan. 1982 [doi>10.1145/357290.357295]

INDEX TERMS

Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.3 Picture/Image Generation
          Subjects: Display algorithms

General Terms:
Algorithms