I'm assuming this is Counter Strike Source here
First of all, you 100% need photoshop for a custom texture. Then just
google "VTF Pulggin Photoshop" and download the plugin and install it.
Then make your texture (make sure the size is a mutiple of 8 on each
side, 128x128,256x256,64x128,etc.).
Now I guess while photoshop is open (because i forgot to add this
before that step), Go to C:\Program
Files\Valve\Steam\SteamApps\*******\counter-strike
source\cstrike\materials
and make a new foler named whatever your map name is. Then go back into
photoshop and save the file as a VTF in the new map folder in the
materials folder. Then go back to materials and click sample and copy a
sample VMT and then paste it in the new map folder. Open up the VMT
and change it to this...
"LightmappedGeneric"
{
"$basetexture" "foldername/texturename"
"$surfaceprop" "concrete"
}
Then just go down to Save, NOT SAVE AS! Go into Hammer and open the
texture browser and then type the beggining of the folder name. You
should see your texture in there. Put your texture where needed.
If done correctly everything should work fine
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