Key changes that have been made include:
·A variant of the func_group entity has been added to the game. When a func_group of brushes (only) is given a terrain key and a numerical value (an ID number for that terrain) and several other key attributes, it becomes a terrain entity and is treated differently than other brushes during the compile.
·The map area has been expanded to 128,000 units in all extents (256,000 units on any edge of the map volume). While this does not mean that a map that large could actually run on current game hardware, it does give the designer room to explore what the actual limits may be. As a point of reference, mpterra2.bsp is roughly 12K x 16K x 3K units in size … the largest map in the game by far.
·A terrain texture mapping system plots textures across the terrain entity using a specially created .pcx or .tga art file as a map for planar projecting and blending shaders on terrain surfaces.
·A “meta-shader” is used to organize and calculate blends between the shaders that are mapped onto the terrain.
·Textures designed for use under vertex lighting can be substituted at map load time for more complex shader-manipulated textures that may not look correct in a vertex light only situation.