The MCPL format
WARNING: This page is under construction or being updated
WARNING: This page concerns documentation for a future release of MCPL and is still being edited
While there are often new releases of the MCPL software distribution, the actual binary MCPL format itself is very stable and rarely receives updates.
Furthermore, since the format version is encoded at the beginning of all MCPL files, it is always possible for the latest MCPL software to read files in older formats (except the format MCPL-1 which was an early format never released to the wider public). This backwards compatibility is obviously an important design feature, intended to ensure that older MCPL files can always be read with the latest MCPL software releases.
List of MCPL formats
- MCPL-1: An early prototype format. This format was never used beyond internal developments and is as undocumented and unsupported as it is unused.
- MCPL-2: The first publicly released format, used briefly around 2015-2016.
- MCPL-3: The default format produced since the MCPL software release 1.0.0 in 2016.
Full format specifications
The actual binary file formats MCPL-2 and MCPL-3 are described in great detail in section 2 of the MCPL paper. As described in the paper, the two formats are in fact almost identical, with the only difference being which packing algorithm is used to pack particle direction vectors. MCPL-3 uses the superior Adaptive Project Packing algorithm, while MCPL-2 uses Octahedral packing.
Conventions
In addition to the actual binary format itself, release 2.1.0 of the MCPL software distribution introduced the notion of a convention for encoding statistics in MCPL headers in comment fields. Crucially, the convention includes a definition of how these statistics should be updated when MCPL files are merged or otherwise edited. Refer to the dedicated page describing the stat:sum convention for more details. Additionally, note than any MCPL comment starting with the 5 characters stat: is considered to be reserved for future usage.