Abstract: A method and apparatus for computing direct lighting in a scene is described. For a sparse set of points in the scene, occlusion information for the points and each of one or more light sources may be computed and stored. For all other surface points in the scene, nearby sample points are examined to determine if their occlusion information agrees. For any light source for which nearby sample points do not agree, lighting computation may be performed, e.g. by the casting of shadow rays. Such areas comprise regions in penumbra or shadow boundaries. For all other regions, it is assumed that they are fully lit or fully occluded, and thus the casting of shadow rays can be avoided.

Abstract: A method and apparatus for diffuse indirect lighting computation in a scene is described. An irradiance caching algorithm may be implemented in an indirect lighting module that sparsely computes irradiance in the environment and then interpolates irradiance values between these sparsely computed points. The method for diffuse indirect lighting computation may use cosine weighting in determining nearby sample irradiance points to be used in interpolation. If an object detected by a ray is directly overhead, embodiments may assume a significant amount of occlusion or indirect illumination of that surface point, and thus may weight the ray more heavily. If an object is off to the side, and thus at a shallow angle to a normal of the surface point under test, the ray is given less weight. By using cosine weighting, the indirect lighting module tends to space out sample irradiance points better around edges and cracks than conventional techniques.

Abstract: An irradiance caching method and apparatus that reduces the number of cache points by determining cache points with appropriately anisotropic areas of influence. At each query point when building an irradiance cache, the irradiance gradients of neighborhood cache points may be determined. If the irradiance gradients of neighborhood cache point(s) along a vector in a particular direction are the same as or similar to the irradiance gradient at the query points, the new cache points are spaced farther apart along vectors in that direction. This results in elliptical regions of influence around cache points in regions around the intersections of two surfaces where the irradiance gradient is changing more rapidly along vectors perpendicular to the intersections and less rapidly or not much at all along vectors parallel to the intersections.