Stereoscopic 3D
Performous supports 3D in various different modes, for devices of various types that can be chosen via the configuration menu.
For each mode you can adjust 3D separation, depending on your screen size and personal preferences for the amount of depth effect. Do not use such high values that make backgrounds appear as two separate images or that strain your eyes. Notice that you currently cannot see the depth in the config menu, so you will need to enter the song browser to see the effect.
This mode requires colored glasses but no other special equipment. If you have red/green, red/blue or red/cyan glasses, choose the red/cyan mode. If you have green/magenta glasses, choose that mode. Performous will automatically reduce saturation when this mode is active because no full color output is possible.
Anaglyph mode requires OpenGL 3.3 and thus it is not supported on Intel GPUs or with open-source drivers. Linux users with AMD or Nvidia GPUs should use the proprietary binary drivers that have support the most recent OpenGL versions up to 4.x.
This mode is meant for 3DTVs and other equipment that can support split screen 3D, normally via active shutter glasses. The top/bottom (over/under) mode needs to be chosen via TV's menus. Performous will only enable 3D when running in full screen mode as it would not work properly in a window anyway. Notice that your desktop will appear garbled when the 3D mode is enabled on the TV.
Users of HDMI 3D-ready equipment can use a hack that allows using 3D without display drivers that support this (GeForce and Radeon lack 3D support on Linux). The trick is to use special modes that HDMI equipment will recognize as 3D modes, and then tell Performous to use Top/bottom mode so that it will display correctly in such mode. Notice that your desktop will appear garbled when such a mode is being used.
To enable custom modes, add the following to xorg.conf:
# 720p60 3D
Modeline "1280x1470_60" 148.5 1280 1390 1430 1650 1470 1475 1480 1500 +hsync +vsync
# 1080p24 3D (not recommended because 24 Hz is too slow and because as the biggest mode it will be used by default)
# Modeline "1920x2205_24" 148.32 1920 2558 2602 2750 2205 2209 2214 2250 +hsync +vsync
To switch modes, use the xrandr tool:
# Set 3D mode 720p60
xrandr -s 1280x1470
# Restore normal 1080p60
xrandr -s 1920x1080
Notice that the height of the 3D modes is more than twice the usual height. This is to allow for a blanking space in the middle. Performous will automatically detect when it is being run in one of these modes and add the appropriate black bar.
On Windows it might be possible to use Nvidia's driver-driven 3D support with Performous without actually enabling Stereo3D in Performous itself. Please refer to Nvidia documentation for details.
http://www.nvidia.com/object/3d-vision-main.html