HVA
HVA files (Hierarchical Voxel Animation, file extension .hva) contain additional information regarding a voxel model: section position, section rotation, and frame count. As its name suggests, HVA allows the voxel model to be animated when multiple frames are defined. In-game, a voxel unit is animated when moving, or in case of jumpjet units in RA2/YR, both when moving and hovering.
Each HVA frame has its own position and rotation offsets for every section in the voxel model. By manipulating these offsets, you can produce a smooth animation across the frames.
Examples of animated models include the Mammoth Mk. II in TS and the Siege Chopper in YR.
Note that HVA files are essential; when the game loads a voxel file (e.g. tank.vxl), if it doesn't find the accompanying HVA file (tank.hva), the game will crash.
