Can't change brightness

[Findus23]

Hello, I am having an issue with playing Portal 2 on my laptop. Everything works fine except that I can't change the brightness. The hole game is very dark and the Setting doesn't change anything. It doesn't matter that much in most levels, but Chapter 5 Turret Manufacturing is hardly playable.

I am using Debian Testing and a HD Graphics 520. System Information and Screenshots: https://gist.github.com/Findus23/8a1bd8e76f6518cb81b4e3ad60304a68

[Tele42]

Howdy, do you have 32bit libtxc-dxtn installed via your package manager?

[Findus23]

Hello, Thanks for the quick answer. It seem that it was already installed (as well as the 64 bit version).

lukas@notebook:~$ sudo apt-get install libtxc-dxtn0:i386
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'libtxc-dxtn-s2tc0:i386' instead of 'libtxc-dxtn0:i386'
libtxc-dxtn-s2tc0:i386 is already the newest version (0~git20131104-1.1).
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.

[Findus23]

Small update: It seems that the original Portal-Game is having the same issue: (although it is less extreme as there are less dark areas)

[aude]

Having the same issue at Fedora, everything is super dark.

$ dnf list installed | grep libtxc
libtxc_dxtn.i686                      1:1.0.1-1.gitef072983.fc23
libtxc_dxtn.x86_64                    1:1.0.1-1.gitef072983.fc23

[dandels]

I'm having the same issue on Arch Linux using the native Steam runtime.

dee ~ pacman -Qs lib dxtn
local/lib32-libtxc_dxtn 1.0.1-5
    S3 Texture Compression (S3TC) library for Mesa (32-bit)
local/libtxc_dxtn 1.0.1-6
    S3 Texture Compression (S3TC) library for Mesa

[Lokoyote]

I have the same issue on Ubuntu 16.04 with an Intel Kabylake GT2. "mat_monitorgamma*" command lines don't change anything.

[Lokoyote]

I propose a small fix :

1. First, disable Redshift/F.lux
2. Modify the "portal2.sh" in "~/.steam/steam/steamapps/common/Portal 2"
3. Add "xgamma -gamma 1.6" (without the quotation marks) between "cd "$GAMEROOT"" and "STATUS=42"
4. Add "xgamma -gamma 1" before "exit $STATUS" to restore gamma

(Based on that source : https://wiki.archlinux.org/index.php/Steam/Game-specific_troubleshooting#Brightness_slider_not_working)

I replaced xrandr by xgamma because xrandr was no effect.

[fosskers]

The above trick worked for me, although I set gamma to 1.3 instead.

[ansipunk]

Had the same issue. The light sources just didn't work, the only light I was getting was the global illumination. Added -vulkan to startup options and it's all fine now. Thought it might be the same issue like in Left 4 Dead 2, where you had to add use_stencil = 1 to video.cfg, but seems like it's not the case since googling "portal 2 use_stencil` yielded nothing related.

[pluiedev]

EDIT: Forcing the game to use Vulkan by specifying the -vulkan startup flag actually fixed the issue and made the game run smoother. Didn't expect the game to run so badly in modern systems with OpenGL, not gonna lie...

---

Wayland user here — adjusting the gamma value with xrandr/xgamma does absolutely nothing under Xwayland, and your best bet is probably trying to adjust the gamma correction settings that may or may not exist, depending on the compositor. Wayland, as always, is a beautifully fragmented mess...

For GNOME, zb3/gnome-gamma-tool worked well for me, although there are probably other tools for other DEs/compositors.