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Most of the consoles higan emulates were designed for the low resolution of NTSC televisions, and their video output is often chunky and blocky by today's standards. Shaders customise how a console's video output is drawn to the computer screen, and can apply just about any effect you can imagine.
For most drivers, the only shaders available are:
- None draws each computer pixel in the same colour as the nearest console pixel. This is sometimes called "nearest neighbour scaling", and produces crisp, blocky output.
- Blur draws each computer pixel as the weighted average colour of the four nearest console pixels. This is sometimes called "bilinear scaling", and hides some of the blockiness at the expense of blurring edges.
However, the OpenGL driver supports custom shaders, in addition to the above.
Note: For technical reasons, higan's emulation of certain consoles can produce surprising behaviour in certain shaders, particularly shaders that compare each console pixel with its neigbours. See Console-specific Notes for details.
Where to get shaders
- higan includes some simple example shaders. If your copy of higan did not come with shaders, you can get them from the unofficial higan repository.
- quark-shaders contains many high-quality shaders for use with higan.
- You can write your own.
How to install shaders
Make sure the shader you want to install
is in the correct format:
it should be a folder whose name ends in .shader,
it should contain a file named manifest.bml,
and probably some *.fs or *.vs files.
Place the shader folder inside
the Video Shaders directory
of your higan installation.
If you don't have a Video Shaders directory,
create it beside the *.sys directories
like Game Boy Advance.sys and Super Famicom.sys.
- On Windows,
this is probably the directory containing
higan.exe - On Linux,
this is probably
~/.local/share/higan
Launch higan, open the Settings menu, and choose "Advanced ..." to open the Advanced tab of the Settings dialog. Under "Driver Selection", make sure "Video" is set to "OpenGL". If you changed the video driver, you'll need to restart higan for the change to take effect.
Open the Settings menu again, choose the "Video Shader" submenu, and now the shaders you installed should be listed at the bottom of the menu.
Load a game (so you can see the results) and switch between shaders to see what they do and pick your favourite!
Notable examples
The quark-shaders repository contains lots of carefully-crafted shaders, but some are particularly noteworthy:
- AANN implements "anti-aliased nearest neighbour" scaling. If the console's video is not displayed at an exact multple of the console's native resolution, rounding errors cause normal nearest-neighbour scaling to draw some rows and columns wider than others, which many people find ugly and distracting. This is very common when higan's aspect-ratio correction mode is enabled. AANN uses very slight anti-aliasing to hide the rounding errors, leaving the overall image as crisp as nearest-neighbour.
- Gameboy emulates the squarish aspect-ratio greenish-colours and limited palette of the original Game Boy. At larger scales, you can even see the fine gaps between each pixel, and the shadow that dark colours would cast on the LCD background.
- NTSC performs NTSC encoding, bandwidth limiting, and NTSC decoding of the video image to recreate the colour fringing, blurring and shimmer that most game players would have seen on real televisions. This is important because some games depended on NTSC artifacts to display colours outside the console's official palette or to create effects like transparency.