Mode 13h: MS-DOSify!

An Iris shader pack for Minecraft that recreates the look of late-90s MS-DOS 3D graphics with deliberate retro accuracy.

Mode 13h: MS-DOSify! is not just a generic “pixelation” shader. It aims to reproduce the actual visual limitations and quirks that gave old DOS-era 3D games their unmistakable look: low resolution, wobbly software texture mapping, a fixed 256-color palette, colormap lighting, billboarded sprites, and vanilla-accurate fog.

It supports the long-term Minecraft versions 1.20.1, 1.21.1 and 1.21.11 with Iris or Oculus; every release is tested on all three. 26.x and other versions are best-effort.

Recommended render resolution: 1280 x 800
The shader pack is designed to downscale by 4x to an internal 320 x 200 image, matching classic Mode 13h output.
For the most authentic look, stretch the final image to 4:3 to reproduce the era’s non-square pixels.

🧾 Why This Exists

A lot of “retro” shaders stop at chunky pixels and call it a day.

Mode 13h goes further. It tries to recreate the specific rendering artifacts that defined old DOS-era 3D, including the quirks modern graphics usually try to hide or eliminate. The goal is not just to look old — it is to feel like an actual late-90s PC pushing textured 3D slightly beyond its comfort zone.

✨ Features

📺 Authentic low-resolution output

• The image is downscaled to a Mode 13h-style 320 x 200 internal resolution.
• This gives the shader pack the crunchy image structure typical of classic DOS graphics.
• Textures pick their mipmaps for that 320 x 200 image, so distant surfaces don't shimmer.

🧱 Quake-style texture mapping

• Like Quake, textures are perspective-correct only every 16 pixels and linear in between, giving the subtle texture wobble of software-rendered 3D.
• Want the full PlayStation-style warping? Switch to affine mapping. Prefer it clean? Perspective-correct is there too.

🎨 A real 256-color palette

• Every pixel is drawn from a fixed 256-color palette, like a DOS game's own.
• The default ramp palette has 16 Minecraft hues (stone, dirt, grass, water, lava, gold…) in 16 shades each.
• Prefer the classic? Pick the stock VGA palette, or the computed RGB332 and 6 x 6 x 6 palettes.
• Or play in the colors of a classic: Wolfenstein 3D, Doom, Heretic, Hexen, Quake, Duke Nukem 3D, Daggerfall, or the Mac OS system palette.

💡 Colormap lighting

• Textures only use palette colors, and shadows step down each color's ramp instead of dimming smoothly — just like the colormaps of Doom and Quake.
• Light is quantized into configurable brightness steps; 16 matches vanilla Minecraft’s light levels.

🌫️ Vanilla-accurate fog

• Fog matches vanilla on each Minecraft version (curve, distance shape, render-distance fog), and clouds fade out like vanilla's.
• Start and End scales push it thicker or farther; set Start to 0.50 for the denser fog of 2.x.

🪧 Billboarded sprites

• Flowers, grass and saplings, mushrooms, kelp, seagrass and coral, cave vines, sugar cane, pointed dripstone, torches, lanterns, chains, amethyst, bamboo and hanging propagules render as 2D billboards that always face the player.
• This mimics the sprite-based tricks commonly used in older 3D games.
• Signs and more blocks can billboard too, with the add-ons below.

✋ Painted viewmodel

• First-person hands and held items are drawn flat and unlit, like the painted weapon sprites of old shooters.
• An ordered dither at 320 x 200 scale breaks up their gradients before the palette.

💧 Night water

• Water turns darker and more opaque in low light, so rivers and oceans read as black depths at night.

⚙️ Configuration

The shader includes a configuration menu with several options so you can fine-tune the effect to your taste.

You can adjust things such as:

• Pixel scale (resolution reduction)
• Palette: ramp, stock VGA, RGB332, 6 x 6 x 6, Mac OS, seven classic game palettes, or off
• Colormap lighting, light steps and ambient floor
• Texture mapping: subdivided, affine or perspective-correct, and the span width
• Fog start and end, and Cloud Distance (match your video setting on 1.21.6+)
• Hands: flat sprite look and dithering strength
• Add-on compatibility toggles, which can be enabled or disabled individually

🔧 Technical Notes

• Requires Iris or Oculus. OptiFine is not supported.
• Supported: Minecraft 1.20.1, 1.21.1 and 1.21.11, tested before every release. 26.x and other versions are best-effort.
• Targets OpenGL 4.1, so it can also run on macOS.
• Lightweight: a handful of geometry passes and one final pass, no composites.
• Upgrading from an older major version: settings for removed or renamed options reset to their defaults.

🧩 Add-ons

Mode 13h also has optional companion add-ons that expand the billboarding system.

Important: Add-ons are not included with the shader pack. They must be downloaded separately.

🪧 Flatter Signs

Flatter Signs is a mod that changes signs into cross/hatch models, allowing Mode 13h to billboard them like flowers or grass.

Without the shader pack, those signs simply render as flat cross/hatch objects. With Mode 13h enabled, they become proper DOS-style billboarded signs.

🧱 Billy Boarding

Billy Boarding is a resource pack that changes the .json block models of selected blocks so they become cross/hatch-based and therefore compatible with the shader’s billboarding system.

It covers cakes and candle cakes, flower pots and potted plants, anvils, bells, brewing stands, cactus, crops and fire.

If you install these add-ons, you can enable or disable their dedicated support from the shader configuration screen.

🌌 Recommended with a Stylized Sky

For the best overall presentation, it is recommended to pair Mode 13h with a stylized skybox.

At the moment, the recommended choice is Better Sky. It uses the OptiFine sky format, so it needs the mods Nuit and Nuit Interop.

A bespoke skybox made specifically for Mode 13h may come in the future.

❌ What It Is Not

• Not just a simple “pixelation” filter
• Not a generic CRT-style retro effect: it emulates the signal, not the monitor. No CRT curvature, scanlines or bloom; stretch to 4:3 yourself.
• Not a clean or modernized take on retro visuals

Mode 13h intentionally embraces visual instability, harsh quantization, and awkward old rendering tricks — because that is the whole point.

❓ FAQ

Clouds don't show up on 1.21.1

Sodium draws clouds with its own renderer, which Iris skips, so clouds are missing with every shader pack on 1.21.1. This is not a Mode 13h bug.

To fix it, open your instance folder and add this line to config/sodium-mixins.properties (create the file if it doesn't exist), then restart the game:

mixin.features.render.world.clouds=false

Vanilla clouds then render through the shader.

How do I set the cloud distance? (1.21.6+)

Clouds fade out at Video Settings → Cloud Distance. Shaders can't read that setting, so set Shader options → Fog → Cloud Distance to the same number of chunks. The default, 128, is vanilla's default.

Before 1.21.6, clouds fog at the render distance like terrain, and the option does nothing.

Enchanted items look dark in the hotbar on 26.2

This is an Iris bug on 26.2 and happens with every shader pack (Iris #3348). Hotbar and inventory items are drawn after the world with vanilla's own shaders, so no shader pack code runs on them and Mode 13h can't fix it. It goes away when Iris fixes it.

What is the Ramp palette, and how do the palettes differ?

• Ramp (default): built for this pack. It has 16 Minecraft hues (gray, stone, dirt, wood, sand, grass, foliage, water, sky, red, lava, gold, amethyst, skin, diamond, crimson), each in 16 shades from black to near-white, like Quake's palette. Colormap lighting steps down these ramps, so it keeps Minecraft's colors best.
• VGA: the stock palette a VGA card booted with. It has the 16 EGA colors, a gray ramp and a hue wheel, so it looks generic and saturated, as games did when they had no palette of their own.
• RGB332 / 6x6x6: computed by splitting each channel evenly. They give a uniform color grid with visible banding and no hand-made ramps.
• Mac OS: Apple's 1987 system palette, a 6 x 6 x 6 cube plus red, green, blue and gray ramps.
• Game palettes (Wolf3D, Doom, Heretic, Hexen, Quake, Duke 3D, Daggerfall): the palette each game's 3D world used. Minecraft takes on that game's colors, but some blocks shift hue because those palettes have fewer Minecraft-like ramps.
• Off: full color.

🖇️ Credits

• Shader pack & idea: HandLock_

Licensed under AGPL-3.0-or-later.

🛠️ Development

See AGENTS.md.

“If the textures don’t wobble, it’s not old enough.”