A system, method, and computer program product are provided for focusing computing power to a region of interest that can be changed interactively and arbitrarily during the process of image synthesis. In operation, a problem domain is partitioned utilizing a first selected technique. Additionally, a number of samples to be drawn per partition are assigned utilizing a second selected technique. Furthermore, the assigned number of samples are drawn for each partition, where the samples are generated by only one deterministic sample sequence. Still yet, the partitioning, assigning, and drawing are capable of being repeated such that existing partitions and assignments are capable of remaining unchanged during sampling and a convergence speed is adapted without compromising convergence in at least one of a sequential computing environment or a parallel computing environment. In this way, the convergence of image synthesis is not compromised. In fact, the image synthesis process may converge to the same solution that would have been obtained without interaction.