1. A method for constructing a light transport matrix for a scene, comprising steps for: acquiring a sparse sampling of rows and columns of a light transport matrix of a scene and adding the acquired samples to a current data set; estimating a kernel function from the current data set, wherein said kernel function is a nonlinear function for transforming values of the current data set to reduce a rank of the light transport matrix; applying the kernel function to the current data set to produce a set of transformed values comprising a sparsely sampled transformed light transport matrix; applying a Nyström process to the sparsely sampled transformed light transport matrix to reconstruct a complete transformed light transport matrix; and applying an inverse of the kernel function to the complete transformed light transport matrix to generate a complete light transport matrix of the scene.