Have you ever compiled a map for SFM only to see glowing rainbow blobs everywhere? Or no reflections showing up at all? No worries, with CubeMapper, building cubemaps has never been easier! </infomercial>
CubeMapper is a simple tool that allows building cubemaps (reflections on models and world geometry) without much hassle involved. It uses Portal 2's similar engine to do what SFM always dreamed of doing: allowing amazing reflections in your posters for any map! Before you start wondering why you wouldn't be doing this directly in SFM: it simply doesn't work.  
- Create a map. Place env_cubemaps into it (crank up the resolution of those to 256x256 if you don't mind huge files). Be sure it is saved inside of one of SFM's mod folders (like game/usermod/maps/blah.bsp). The name should not be longer than 30 characters total
- Compile your map using SFM's Hammer Editor (be sure not to rename your file after compiling it!)
- Open CubeMapper.exe
- Drag&Drop the map file you wish to create cubemaps for into the input textbox (or just browse for it)
- If the portal2.exe did not get set automatically, do so yourself
- Go to Edit Mods and make sure only the mods you really need are enabled, since more mods means more loading times, and may cause conflicts (Portal 2 is always loaded)
- If no other warnings show up under the Notes section, press Start and wait for Portal 2 to launch
- Once the map loaded, press F1, sit back and relax
- Once Portal 2 closed itself, go into SFM and enjoy your amazingly reflective map!
Q: Why does the program not launch?
A: CubeMapper requires the .NET Framework 4.5.2 or later. Download here! Also make sure all files from the ZIP are extracted to a folder and not run from inside the archive.
Q: Why does Portal 2 instantly close when I press F1?
A: Your screen resolution probably is too small (width and height have to be >1024 pixels). Add the following lines to the end of the Arguments textbox:
-w 1025 -h 1025 -windowed
Q: Portal 2 crashes on startup?
A: Be sure that CubeMapper is run as an administrator.
Q: Everything is purple-black checkerboards and errors?
A: Portal 2 has to be installed in the same Steam library folder as Source Filmmaker in order for the files to be found, since only relative paths can be used in gameinfo.txt files. You may also simply need to enable the mods which are responsible for the content that is missing (see the Edit Mods dialog).
Q: What if I don't own Portal 2?
A: I personally have never tried, but according to others, Alien Swarm works as well and is free. See if it works out for you!
Q: My map doesn't look reflective! Why do you lie to me?
A: If you follow the instructions above, everything should work out. If you are trying it on a map you didn't compile, it may be related to other files being packed into the BSP or the map simply not having cubemaps to begin with. Shining SFM lights onto your surfaces may also cause them to look less reflective. SFM also seems to cache cubemap data, so try restarting SFM or running
mat_reloadallmaterials after building your cubemaps.
Q: What are these glowing orbs in my reflections?
A: I am not sure what causes them, but they show up on every light entity. It may be intentional, to better show lights in reflections, but who knows.
Q: Can I see the source code?
A: Once someone actually asks this, I'll release it. Since there's not many people interested in that kind of thing, setting up a git repository just for the sake of having it is not worth the effort, in my opinion.