Filter Importance Sampling

High quality ray tracing requires pixel sampling and filtering for antialiasing, as well as illumination sampling for complex lighting effects. Both problems are well understood and sophisticated sampling techniques are available for each of them. However, it turns out that weighted pixel sampling spoils the benefits of clever illumination sampling, even with the best filter functions. We propose to circumvent this problem by using pixel sampling and filtering based on importance sampling. Although this technique disallows sharing of samples between neighboring pixels, it results in significant noise reduction and improvement of image quality. The method is easy to implement and well suited for parallel, tile based rendering