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, affine texture warping, limited color depth, stepped lighting, billboarded sprites, and carefully tuned fog.

It has currently only been tested on Minecraft 1.20.1, but it should also work on other versions.

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.

🧱 Affine texture mapping

• Textures use affine mapping instead of perspective-correct mapping.
• This recreates the classic texture wobble and warping seen in older software-rendered 3D games.

🎨 Retro palette reduction

• Colors are quantized to a 256-color style output.
• An optional 6 x 6 x 6 palette provides a more limited 216-color look.

💡 Stepped lighting

• Lighting is quantized into configurable brightness steps.
• Setting it to 16 steps gives something closer to vanilla Minecraft’s light progression while keeping the retro feel.

🌫️ Tuned fog

• Fog is adjusted to better match the mood and readability of old-school 3D visuals.
• It helps sell distance the way older games often did.

🪧 Billboarded sprites

• Many blocks and decorations render as 2D billboards that always face the player.
• This mimics the sprite-based tricks commonly used in older 3D games.

⚙️ 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:

• Fog tuning parameters
• Affine mapping parameters
• Color reduction mode, including switching between 256-color and 216-color
• Add-on compatibility toggles, which can be enabled or disabled individually
• Resolution reduction
• And other settings for dialing in the exact retro look you want

🔧 Technical Notes

• Built for Iris and compatible with Oculus
• Currently only tested with Minecraft 1.20.1, though it should work on other versions as well
• Targets OpenGL 4.1, so it can also run on macOS

🧩 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 (WIP)

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.

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 Anime Sky.

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
• 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.

🖇️ Credits

• Shader pack & idea: HandLock_

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