Tesseraion

Animated Perlin-noise ASCII-art wallpaper renderer, written in C and GLSL ES. Lean, dependency-light, and built to be portable across layer-shell desktops (COSMIC, Hyprland, sway, river) and anywhere GLES runs. Work in progress.

The name

Tesseraion is a coined word, a fusion of two old ones:

• Tessera (Latin, from the Greek "tessares", meaning four): a single small tile in a mosaic, originally a four-sided piece. A finished mosaic is a field of tesserae. This program draws exactly that, a grid of ASCII cells, each one a tile in the larger picture.
• Aion (Greek, "aion"): an age, an eternity, time as something cyclical and unbounded. The field never stops. It flows on a continuous clock with no end and no loop you can quite catch.

Put together, Tesseraion means a mosaic of tiles in endless motion. Tiles out of time. It is also, conveniently, unique

What it does

A fullscreen field of ASCII characters driven by animated Perlin noise. The noise value at each cell picks a glyph and a shade, and the whole field drifts over time. The look is ported from the animated background of my portfolio site.

Build

Requirements: a C11 compiler, make, pkg-config, and the GLFW3 and OpenGL ES development headers. On Arch: pacman -S base-devel glfw mesa.

make          # release build (-O2 -Wall -Wextra -Werror), produces ./tesseraion
make run      # build, then launch the GLFW dev host
make debug    # unoptimized build with symbols (-O0 -g)
make clean

The renderer targets OpenGL ES 3.0 / GLSL ES 3.00 (the same feature set as WebGL2, broadly supported by Mesa). It runs from the repo root so it can find shaders/.

Run

./tesseraion [path/to/config]    # default config path is ./tesseraion.conf

Keys in the dev host:

• Esc quit
• B toggle smooth glyph cross-fading (on) vs one hard glyph per cell (off)

The shader files and the config file are watched while running, so edits apply live (see below).

Configuration

All tunables live in a small key = value file. Start from the documented sample:

cp tesseraion.conf.example tesseraion.conf

Then uncomment and edit keys; save and the running app re-reads the file instantly (the frame cap and everything else update live). # starts a comment, unknown keys are warned and ignored. Keys include the frame cap and speed; the cell metrics (font_size, char_w_ratio, line_h_ratio, max_cols); the ramp; the noise field (noise_scale, warp, softness, skip, alpha_cap, fade_band); the palette (mid_rgb, peak_rgb, blue_start, blue_full, accent_boost); and seed. See tesseraion.conf.example for the full list with defaults and descriptions.

The pattern is randomized on each launch unless you pin it with seed = <number>. Editing speed changes the drift rate without jumping the pattern. Your local tesseraion.conf is gitignored, so tweaking it never dirties the repo.

Architecture

The code is split into a host-agnostic render core and a swappable host, so the visual can be reused unchanged by different windowing backends:

• src/core/ is the render core: it assumes a current GLES 3.0 context and exposes a tiny C API (init, resize, draw(time), shutdown) plus a config apply / hot-reload surface. It owns the shader, the glyph atlas, and all GL state; it never touches windowing, input, or timing.
• src/host/ owns the window, the context, the clock, and input, and drives the core through that API. host_glfw.c is the windowed dev host.
• shaders/ascii.frag is organised as three editable stages (pattern, glyph, palette) and documents the full uniform contract at the top of the file.

This split is deliberate: a layer-shell wallpaper host (COSMIC, Hyprland, sway, river) can be added later as a new host that only supplies its own GLES context, reusing the render core untouched. The exact handoff is documented in src/host/host.h.

Desktop wallpaper hosts

• GNOME (Wayland): gnome/ is a wallpaper host for GNOME Shell, built as a Shell extension plus a native Wayland/EGL host that reuses this render core unchanged. GNOME has no layer-shell, so it takes a different route from the wlroots desktops above. See gnome/README.md.

License

This project is licensed under the GNU General Public License v3.0 or later (GPL-3.0-or-later) - see the LICENSE file for the full text. Every source file carries an SPDX-License-Identifier: GPL-3.0-or-later header.

In plain terms: the code is mine (Captain Mirage) and it is copyleft. You're free to use, study, modify, and share it, but any version you distribute must also be open source under the GPL, keep the copyright and license notices, and state the changes you made. If you build on it, mention me and link back to this repository. Using it without attribution might result in me sneaking into your walls while you sleep.

The bundled font (third_party/font_vera_mono.h) is Bitstream Vera Sans Mono under its own permissive license (see third_party/VeraMono-LICENSE.txt), and third_party/stb_truetype.h is public domain / MIT; both are compatible with the GPL.

(c) 2026 Captain Mirage