EC - Field3D
Field3D is an open-source file format for storing voxel data. It has been developed by Sony Pictures Imageworks and is based on HDF5 to manage large amounts of data of different types. The file format stores both sparse and dense voxel data, as well as procedural fields.
In RealFlow's Hybrido, fields are necessary to describe many different things: the fluid's surface, velocity and collision, to name but a few. This is, for example, required for the creation of secondary particles (splash/foam). By default, the field data is stored in RealFlow's proprietary GFC format, but you can switch to OpenVDB and/or Field3D. Both formats are recognized by RealFlow as cache files and they can substitute GFC completely.
Field3D is completely free of charge and available for download under:
https://sites.google.com/site/field3d/downloads
Field3D is not available for all 3D platforms supported by RealFlow, and in most cases you will only find uncompiled, but free, source code for importer plugins. Here are a few links:Â
Maya (source code) [ https://github.com/magic-box/Field3DMayaPlugin ]
Maya 2014 (compiled) [ https://github.com/GermanMentalRay/GMR/tree/master/maya/plugins ]
Houdini (native support in H12+)
FumeFX (native support in FumeFX 3.5+)
Please also do a search for more information about F3D import plugins.