Instructions:
put the materials and models folders into anon-hl2/hl2. This will add a model called "Frozen_Zombie.mdl" to your game.
If you want your npc_zombies to use this model, open the "Replacement for regular zombie" folder and copy-paste "zombie" into your
models folder. Hit "replace" when prompted. Unfortunately, as of writing, the leak/leaknet does NOT have support for different zombie
models, so it is necessary to replace the "Classic.mdl" file, which will therefor replace all zombies in the game with this. If you
think this is lame, ask VXP if he would kindly change the npc_zombie code so that it has a dynamic model instead of a forced model.
That way, mappers can change what model zombies are using, so, for example, if you wish to have fat zombies in one place and skinny
zombies in another, you could change this in hammer.
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Credits:
Wolfcl0ck - Model, textures
Gmaddador and Sgt Stacker - fixed animations, .qc file