A cache-efficient processor and method for rendering indirect illumination using interleaving and sub-image blur. One embodiment of the processor is configured to render an indirect illumination image and includes: (1) a buffer restructurer configured to organize a reflective shadow map (RSM), rendered with respect to a reference point, into a plurality of unique sub-RSMs, each having sub-RSM pixels, (2) an indirect illumination computer configured to employ interleaved sampling on the plurality of unique sub-RSMs to generate a plurality of indirect illumination sub-images, and (3) a filter operable to smooth accumulated light values of the indirect illumination sub-images for subsequent interleaving into the indirect illumination image.