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2ksbox

The CRT look

Games of the era were drawn for a CRT monitor. Their pixels were meant to blur into each other a little, with scanlines and a glow. On a flat panel, stretched to fit, they look blocky and soft at the same time.

2ksbox takes the machine’s own picture, at its own resolution, and runs it through a CRT shader before it reaches your screen. The shaders come from libretro’s collection, the same ones RetroArch uses.

Shader profiles

Section titled “Shader profiles”

A shader profile is a shader preset plus your own adjustments to it, under a name. The download on first start adds three:

  • CRT Aperture, a sharp aperture-grille look. It’s the default.
  • CRT Royale, a detailed CRT with a phosphor mask and glow. It needs a strong graphics card and looks better with a custom configuration.
  • Apple II, the classic green phosphor monitor. You can configure it with other colours. It looks cool on a text-only screen, like MS-DOS.

Open Shader Profiles to see them. The switch in the Default column marks the profile that every machine set to “(default)” uses. No default clears it, and those machines then show the picture with no shader.

Make your own

Section titled “Make your own”
  1. In Shader Profiles, click New.
  2. Type a Name and pick a Preset (.slangp). The collection has hundreds, in folders by kind. The crt folder is the place to start.
  3. Pick a Preview image: a screenshot of a game you play. The preview shows it through the shader as you change things. The Scale slider shows it at the size you’ll play at.
  4. Adjust the preset’s parameters until it looks right.
  5. Click Save.

A good preview image is one the player saved with Ctrl+Alt+S (⌥⌘S on macOS). It is the machine’s raw display output, before the shader.

Pick a profile for a machine

Section titled “Pick a profile for a machine”

In the machine’s settings, on the Display page, set Shader profile. “(default)” follows whatever profile you marked as the default, so changing the default changes every machine set to it. Off shows the machine with no shader at all, whatever the default.

While a machine runs, View > Shader in its window swaps the profile at once. The machine keeps the new one.

A Windows 11 machine starts with no shader, because a modern desktop is meant for a flat panel.

How the player scales the picture

Section titled “How the player scales the picture”

The player keeps the machine’s picture in proportion and adds black bars rather than stretching it. 320×200 games get the 4:3 shape they had on a monitor.

The View menu’s Scale chooses the size:

  • Largest That Fits fills the window as far as whole steps allow.
  • 1x to 4x show each of the machine’s pixels as exactly that many of yours. Retina screens have more steps. A size that doesn’t fit the window is cropped.
  • Fit Window to Picture sizes the window to the picture.

Whole steps matter for a CRT shader: its scanlines land on the same rows of your screen every time, so the picture doesn’t shimmer.