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environment mappingr - Environment Mapping Environment maps...

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Environment Mapping Environment maps represent images of complex environment around objects. There are different ways to capture and store them. Spherical Maps and Mapping Principle Spherical maps are reflection of the environment on a mirror sphere, and are stored in a single texture. The mapping step assumes that the rendered objects are placed exactly where the sphere was during the capture. The directions (mirror reflection, or incident light direction at any surface point) from the object are mapped into the texture pixel position using the following equation: where R is the vector of interest. This formula means that the entire surface of the sphere is mapped within the inscribed circle of 1.0x1.0 square.
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The figure on the left shows the cross section of a sphere on which the environment is mapped. In this example, the eye point is placed at the right hand side of the figure. Each point on the sphere's cross section is connected to a point on the plane by a white line. The figure on the right shows an orthogonal view of the texture plane referred to in the left figure. The inside circle represents the front half of sphere, which is the right half of left figure. The outside circle represents the back half of the sphere. Advantages of this method is that only a single texture access is required for texture mapping, and the spherical map contains only one point of singularity (0,0,-1). The directions are assumed to be in the eye co-ordinate system. Light Probe Maps and Mapping Principle Light probe maps are a special case of sphere maps. They are available from www.debevec.org/probes. Light probe images are created by taking two pictures of a
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