In old TR games, AnimCommands were the ones responsible for sound effects, intermediate position changes and rotation, and various effects linked to animations. Support of these AnimCommands can be considered milestone in OpenTomb development, as it prepares the ground for such features as long-awaited OpenAL implementation. Also, we can finally get rid of some "filler" hardcoded state control code.
There were, however, some troubles with making AnimCommands work in engine. Classic TR level structure kept all animation frames in single solid array, dividing them by "FrameStart" and "FrameEnd" parameters for each animation. Same thing applies for AnimCommands, as natively they used same absolute frame index; the thing is, OpenTomb behaves differently, specifying relative frame indexes for each animation (which is much more human-readable and easy). What we needed is to make simple parser, which converted absolute frame indexes to relative.