Computer graphics apparatus, methods, systems and program products (the term “programs” can include a product consisting of computer-readable program instructions encoded on a computer readable medium) operable to generate pixel values for pixels in an image, and store or display a human-perceptible image based on the pixel values, comprise a photon map generator, a sample point generator and a function evaluator, which respectively generate a plurality of photon maps each associated with a respective point in time during a time interval, generate a set of sample points in accordance with a selected low-discrepancy sequence, and evaluate selected functions using photon maps associated with respective points in time associated with the sample points, thereby generating values corresponding to the pixel values. An associated computer system generates, based on the pixel values, a display-controlling electrical output to enable a display element to display an image.