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Chunks of voxel data are stored in a map, and it is quite common to need to search the map for a particular chunk. The key type used to be a Vector3D (i.e. the position of the chunk in 3D space) which makes conceptual sense but is relatively slow. Using a Vector3D as a key seems to have overhead, probably in terms of copying and performing comparisons. It seems to be significantly faster to use an integer as a key, so we now take the 3D position and pack it into a single integer by bitshifting. Naturally this reduces the range of positions we can store - a 32-bit int can only encode 3 x 10-bit values, which means our volume can only be 1024 chunks in each direction (with a chunk often being 32x32x32 voxels). This should still be large enough for most uses, but an upcoming change will allow 64-bit keys to be used (at least on 64-bit builds) which then allows 21 bits of precision per component. This is so large that it's almost infinite for any practical purposes.
PolyVox - The voxel management and manipulation library ======================================================= PolyVox is the core technology which lies behind our games. It is a fast, lightweight C++ library for the storage and processing of volumetric (voxel-based) environments. It has applications in both games and medical/scientific visualisation, and is released under the terms of the `zlib license <http://www.tldrlegal.com/l/ZLIB>`_. PolyVox is a relatively low-level library, and you will need experience in C++ and computer graphics/shaders to use it effectively. It is designed to be easily integrated into existing applications and is independent of your chosen graphics API. For more details please see `this page <http://www.volumesoffun.com/polyvox-about/>`_ on our website.