![]() ![]() This second environment map is known as the diffuse irradiance environment map (or just the diffuse environment map), and it allows us to illuminate objects with arbitrarily complex lighting environments with a single texture lookup. #Radiance v and make visuals great again Offline#What this means is that we can compute the sum for any normal n in an offline process executed once per environment map, and store the result in a second environment map, indexed by the surface normal. Second, the sum is dependent on just the lights in the scene and the surface normal. Looking at Equation 10-1, we notice a few things: First, all surfaces with normal direction n will return the same value for the sum. What we would like is a mechanism for precomputing the diffuse reflection, so that the per-pixel rendering cost is independent of the number of lights/texels. This provides an efficient mechanism for storing arbitrarily complex lighting environments however, the cost of computing B increases proportionally to the number of texels in the environment map. In this context, an environment map with k texels can be thought of as a simple method of storing the intensities of k directional lights, with the light direction implied from the texel location. Given the standard OpenGL and DirectX lighting equations, the resulting pixel intensity B is computed as: i k, illuminating a diffuse surface with normal n and color c. Imagine a scene with k directional lights, with directions d 1. For brevity, this chapter assumes that the reader has working knowledge of environment maps, particularly cube maps (Voorhies and Foran 1994) and dual-paraboloid maps (Heidrich and Seidel 1998). This technique enables applications to quickly approximate complex global lighting effects in dynamic environments (such as radiosity from dynamic lights and dynamic objects). This chapter describes a fully GPU-accelerated method for generating one particularly graphically interesting type of environment map, irradiance environment maps, using DirectX Pixel Shader 3.0 and floating-point texturing. ![]() ![]() Real-Time Computation of Dynamic Irradiance Environment MapsĮnvironment maps are a popular image-based rendering technique, used to represent spatially invariant spherical functions. The CD content, including demos and content, is available on the web and for download.Ĭhapter 10. You can purchase a beautifully printed version of this book, and others in the series, at a 30% discount courtesy of InformIT and Addison-Wesley. GPU Gems 2 GPU Gems 2 is now available, right here, online. ![]()
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