Portal is a first-person puzzle game. Players must solve physical challenges by opening portals to maneuver objects, and themselves, through the enigmatic Aperture Science Laboratories.
This is a large multi-layered picture in pdn/vtf/png (png not layered) format that allows people to create custom testchamber signs for Portal when used correctly. Please give credit to Nick Pendergrass for this addon. **REQUIRES PHOTO EDITING SOFTWARE AND VTF EDITING SOFTWARE**
This is a large multi-layered picture in pdn (PAINT.NET)/vtf/png (png not layered) format that allows people to create custom testchamber signs for Portal when rearanged and cut correctly. When you have the texture you are looking for, save it as an image format that can be read by a VTF creating program for future conversion or as a VTF. After creation, make a coresponding VMT file and open hammer. In hammer, create a block in your map that is the same size as the official Portal testchamber signs with no depth. Apply the texture and fit it to your block. Add the depth now so that the center is 1 unit in and a frame is left around it. The sides will still be blank. Extract the 'materials' folder to 'STEAMDIR/steamapps/**username**/portal/portal/*. Go back to hammer. Apply the sides to the texture "NTSC/sign_border". Good job. Be advised, that this sign will not flash on like the regular Portal signs unless the user has made a multi-layered texture of the turn on or has applied this texture to a model as multiple skins. Both of those are also possible with this addon (if you have a model making program). Goodbye.
Have fun! Please give feedback (and credit)!
PS, be sure to check out Portal: Revolution. I'm the new mapper! :D Link - Moddb.com