1. A method for distributing workload in a ray tracing image processing system, the method comprising: dividing a two-dimensional frame of pixels into at least a first region of pixels and a second region of pixels, wherein the two-dimensional frame of pixels represents an image rendered from a three-dimensional scene; partitioning a spatial index, wherein the spatial index represents the three-dimensional scene; assigning to a first processing element a responsibility for initiating ray tracing for rays that traverse through the first region of pixels; assigning to a second processing element a responsibility for initiating ray tracing for rays that traverse through the second region of pixels; performing ray tracing with the first processing element and the second processing element to determine colors of pixels in the two-dimensional frame of pixels; monitoring at least one of a workload experienced by the first processing element and a workload experienced by the second processing element; re-dividing the two-dimensional frame of pixels into at least a new first region of pixels and a new second region of pixels based on at least one of the workload experienced by the first processing element and the workload experienced by the second processing element; and re-partitioning the spatial index based on at least one of the workload experienced by the first processing element and the workload experienced by the second processing element.