Yeah dude he’s right you need Alien Swarm and its SDK and before starting the mapping you should set the SDK in the Alien Swarm tools. You will find the “Gameconfig.txt” file in this path “C:\Program Files\Steam\steamapps\common\alien swarm\bin” you have to paste the following code after the second bracket under the Alien Swarm,
Code:
"Portal 2 - Unofficial"
{
"GameDir" "c:\program files\steam\steamapps\common\portal 2\portal2"
"Hammer"
{
"GameData0" "c:\program files\steam\steamapps\common\alien swarm\bin\portal2.fgd"
"TextureFormat" "5"
"MapFormat" "4"
"DefaultTextureScale" "0.250000"
"DefaultLightmapScale" "16"
"GameExe" "c:\program files\steam\steamapps\common\portal 2\portal2.exe"
"DefaultSolidEntity" "func_detail"
"DefaultPointEntity" "info_player_start"
"BSP" "c:\program files\steam\steamapps\common\alien swarm\bin\vbsp.exe"
"Vis" "c:\program files\steam\steamapps\common\alien swarm\bin\vvis.exe"
"Light" "c:\program files\steam\steamapps\common\alien swarm\bin\vrad.exe"
"GameExeDir" "c:\program files\steam\steamapps\common\portal 2"
"MapDir" "C:\Program Files\Steam\steamapps\username\sourcesdk_content\portal2"
"BSPDir" "c:\program files\steam\steamapps\common\portal 2\portal2\maps"
"PrefabDir" "C:\Program Files\Steam\steamapps\username\sourcesdk_content\portal2\Prefabs"
"CordonTexture" "tools/toolsskybox"
"MaterialExcludeCount" "0"
}
}
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