1. A method comprising: traversing a plurality of nodes within a spatial hierarchy, the spatial hierarchy representing a scene which is to be rendered and the spatial hierarchy including at least two hierarchy levels, each of the hierarchy levels of the spatial hierarchy including at least one node; for each of the hierarchy levels of the spatial hierarchy, storing a number representing the number of nodes traversed in the hierarchy level, wherein each of the numbers is represented by at least one bit in a multi-bit binary sequence, and wherein the multi-bit binary sequence consists of the bits representing the numbers, and the numbers are concatenated; and identifying, based upon the multi-bit binary sequence, a node of the spatial hierarchy which is to be visited next upon restart of the spatial hierarchy traversal.