---
title: The Matrix digital rain
date: 2024-01-12
thumbnail: thumb.png
layout: post
---

"All I see is blonde, brunette, red head." The iconic digital rain from The
Matrix in C, with zero dependencies - not even ncurses.

<video style="max-width:100%;" controls="" poster="thumb.png">
  <source src="matrix.mp4" type="video/mp4">
</video>

## Overview

This is my fork of Domsson's beautiful <a
href="https://github.com/domsson/fakesteak" class="external" target="_blank"
rel="noopener noreferrer">Fakesteak</a>. While studying the code, I wondered
what it would take to faithfully recreate the original Matrix from the first
movie without sacrificing the program's minimalism and elegance.

My version adds:

 - Unicode character support.
 - Fully customizable 24-bit RGB (truecolor) colors.
 - Glitches in the matrix.
 - Ghosting effect of old monochrome CRT displays.
 - Closely resembles the Matrix seen in the background during Neo and Cypher's
   conversation.

With no dependencies, compilation is trivial:

```
$ cc -O3 main.c -o matrix
$ ./matrix
```

## How does it work?

The program tracks the state of the terminal - characters, background and
foreground colors, shading levels, cursor position - using multiple internal
data buffers. On each frame, it updates these buffers and repaints the screen
using ANSI escape codes:

```
static void term_print(const matrix *mat, size_t row, size_t col)
{
    size_t idx;
    idx = mat_idx(mat, row, col);
    wprintf(L"\x1b[%d;%dH\x1b[38;2;%d;%d;%dm%lc",
        row, col,
        mat->rgb[idx].color[R],
        mat->rgb[idx].color[G],
        mat->rgb[idx].color[B],
        mat->code[idx]);
}
```

The ghosting effect, the signature feature of this implementation, works by
scaling and mixing the RGB channels:

```
static void mat_shade(matrix *mat, size_t row, size_t col) 
{
    unsigned char *color;
    color = mat->rgb[mat_idx(mat, row, col)].color;
    color[R] = color[R] - (color[R] - COLOR_BG_RED) / 2;
    color[G] = color[G] - (color[G] - COLOR_BG_GRN) / 2;
    color[B] = color[B] - (color[B] - COLOR_BG_BLU) / 2;
}
```

The ghosting function emulates the screen decay by gradually transitioning each
raindrop's color towards the background color. This approach provides two key
benefits: straightforward color configuration that integrates naturally with
Unix ricing (desktop customization) and high-fidelity recreation of the Matrix
aesthetic.

## Customization

While you can adjust almost every aspect, including its speed, glitch
frequency, and rain density, the most useful settings for customization are the
color scheme and character set.

There are three color settings: head, tail, and background. You can configure
them by setting the `COLOR_*_RED`, `COLOR_*_GRN`, and `COLOR_*_BLU` definitions
in main.c. 

The `UNICODE_MIN` and `UNICODE_MAX` values control the Unicode block used. For
example, setting them to `0x30A1` and `0x30F6` rains Katakana (if a font that
supports Katakana is present on the system):

<img style="width: 100%;" src="katakana.png" />

Files: [source.tar.gz](source.tar.gz)