so i have the whole canal part of HL2 decompiled into vmf format and i went to the part where you slide down the mudslide and almost get eaten by the barnacles....with their hanging tounges. there were no triggers in sight so i figured it was a vmt setting. got the vmt for the slime texture and opened it up.
im guessing the "$surfaceprop" "slipperyslime" part would make it so that the texture is slippery. too bad since it doesnt seem to let you change the magnitude of the "slipperyness". not exactly sure if itl work...but give it a try.
yeah when you add vmts, youll get access to the texture whos vmt you modified AND the texture whos vmt is the way it is in the gcf. they may look identical, but one texture has the vmt properties that YOU gave it and the other has the vmt properties VALVE gave it. how can you tell the difference between the two? look at the names of the folder they are in when you are in the texture browse menu (its says below the texture). one will be the original and the other will be in the custom folder you made in your materials directory.