Some embodiments relate to a machine-implemented method of packing volumetric image data executed by at least one processing device, the method comprising: determining a first block size; writing to memory a first block of image data from a first image, the first block having the first block size; determining a second block size; and writing to memory a second block of image data from a second image, the second block having the second block size; wherein the first image contains X by Y pixels of one of colour data and depth data, and the second image contains X by Y pixels of the other of colour and depth data; and wherein the first image is related to the second image. Embodiments also relate to methods of unpacking volumetric image data. Further embodiments relate to systems and computer-readable media storing or having access to code to execute the packing and unpacking methods.