This is a Linux-only project, as the hack depends on a shared glibc library for extracting the original trig functions, and uses LD_PRELOAD to inject itself into the game. You can probably do this on Windows, but this code won't be of any help to you.

You'll need 32-bit compatible gcc to compile, which you likely already have. There are no other dependencies. Run build.sh, and it should generate pi4.so and sinswap.so. You can use file to make sure it reports an "ELF 32-bit LSB shared object".

1. Move the libraries into your "Portal 2" directory.
2. Edit portal2.sh to add export LD_PRELOAD=pi4.so right under cd "$GAMEROOT"
3. Lock your pitch at 0deg in-game with console commands cl_pitchup 0 and cl_pitchdown 0

If using sinswap.so or some other unstable build, you may use the ""physics engine"" I hacked together in 10 minutes. It's nothing more than basic collision detection and gravity simulation. To install it, move the portal2_dlc4 directory in this repository to your Portal 2 folder. If you don't already have a portal2_dlc3 there, rename it to that. If you already have portal2_dlc4 or higher, rename it to the lowest available number. Then, when in game, before opening a map, run sv_cheats 1 and phys_timescale 0 to disable the game's existing physics.

Please don't. I don't intend on checking pull requests or issues.