Fast Phong shading

  • Authors:
  • Gary Bishop;David M. Weimer

  • Affiliations:
  • -;-

  • Venue:
  • SIGGRAPH '86 Proceedings of the 13th annual conference on Computer graphics and interactive techniques
  • Year:
  • 1986

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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.