Vol. 7, No. 4: 3—8 Simple Blurry Reflections with Environment Maps Michael Ashikhmin and Abhijeet Ghosh SUNY at Stony Brook Abstract. We present a technique which uses existing OpenGL capabilities to ap- proximate the effect of blurry specular reflections and indirect diffuse illumination. It makes use of environment maps, mipmapping with level of detail control, and possibly texture borders. The method is extremely simple to implement, in some cases requiring just a single additional OpenGL statement. 1. Introduction Physically based rendering systems describe surface reflection behavior using the bidirectional reflectance distribution function (BRDF). They then use it as a weighing function applied, along with an extra cosine term, to the illumi- nation incident upon the surface to compute the final color using the rendering equation [Kajiya 86]. This process can take into account light coming from all objects in the scene (indirect illumination) rather than only directly from light sources (direct illumination). In recent years, substantial research effort has been directed at incorporating both arbitrary BRDFs and indirect illu- mination effects into hardware-based rendering [Cabral et al. 99], [Heidrich and Seidel 99], [Ramamoorthi and Hanrahan 01]. In most cases, however, the techniques proposed are rather complex and require significant extra program- ming effort to implement. On the other hand, it is well known that accurate computation of these effects is not critical for most applications as long as the main character of the BRDF and illumination are both correctly reproduced. This led to the development of numerous ad-hoc approximation techniques © A K Peters, Ltd. 3 1086-7651/02 $0.50 per page