Abstract: A computer implemented method of building an acceleration structure for use in ray tracing includes (i) assigning, in a memory, a different one or more blocks of memory to each of a plurality of threads, each of the blocks of memory comprising one or more memory locations; (ii) for each element of a plurality of elements of a scene for which nodes of the acceleration structure are to be built, assigning that element of the scene to a block of memory so as to assign that element to a thread; and (iii) building one or more nodes of the acceleration structure by processing each of the plurality of threads in parallel.