Flitter

Flitter is a functional programming language and declarative system for describing 2D and 3D visuals. It is designed to encourage an iterative, explorative, play-based approach to constructing visuals.

The language supports the basic range of functional language features: first-class recursive and anonymous functions, comprehensions, let/where, conditional expressions, lists ("vectors"). However, unusually, all values are vectors and all operators are element-wise, and the language is built around constructing trees of attributed nodes. The language is designed to be familiar to Python programmers.

The engine is able to live reload all code and assets (including any shaders, images, videos, models, etc.) while retaining the current system state - thus supporting live-coding. It also has support for interacting with running programs via MIDI surfaces (plus basic pointer and keyboard support).

Flitter is implemented in a mix of Python and Cython and requires at least OpenGL 3.3 (Core Profile) or OpenGL ES 3.0. At least Python 3.10 is also required as the code uses match/case syntax.

Flitter is designed for expressivity and ease of engine development over raw performance, but is fast enough to be able to do interesting things.

The engine that runs the language is capable of:

• 2D drawing (loosely based on an HTML canvas/SVG model)
• 3D rendering, including:
  • primitive box, sphere, cylinder and cone shapes
  • external triangular mesh models in a variety of formats including OBJ and STL
  • planar slicing, union, difference and intersection of solid models
  • ambient, directional, point/sphere, line/capsule and spotlight sources (currently shadowless)
  • multiple (simultaneous) cameras with individual control over location, field-of-view, clip planes, render buffer size, color depth, MSAA samples, perspective/orthographic projection, fog, conversion to monochrome and colour tinting
  • PBR forward-rendering pipeline with emissive objects, transparency and translucency, plus the ability to plug in custom GLSL shaders for arbitrary groups of objects
  • texture mapping, including with the output of other visual units (e.g., a drawing canvas or a video)
• simulating physical particle systems, including spring/rod/rubber-band constraints, gravity, electrostatic charge, adhesion, buoyancy, inertia, drag (including in flowing media), Brownian motion, uniform electric fields, barriers and particle collisions
• playing videos at arbitrary speeds (including in reverse)
• running GLSL shaders as stacked image filters and generators, with per-frame control of arbitrary uniforms, and support for multi-pass and downsampling
• built-in filters for: scaling/translating/rotating, Gaussian blurring, bloom, edge detection, vignetting, video feedback, lens flares, color and exposure adjustments, tone-mapping with the Reinhard and ACES Filmic functions, and 2D noise-map generation
• compositing all of the above and rendering to one or more windows
• saving rendered output to image and video files (including lockstep frame-by-frame video output suitable for producing perfect loops and direct generation of animated GIFs)
• taking live inputs from Ableton Push 2 or Behringer X-Touch mini MIDI surfaces (other controllers relatively easy to add)
• driving arbitrary DMX fixtures via an Entec-compatible USB DMX interface
• driving a LaserCube plugged in over USB (other lasers probably easy-ish to support)

Flitter also has a plug-in architecture that allows extension with new image and 3D mesh generators, MIDI and DMX interfaces, or completely novel input and output systems.

Installation

Flitter can be installed from the flitter-lang PyPI package with:

pip3 install flitter-lang

and then run as:

flitter path/to/some/flitter/script.fl

More details can be found in the installation documentation.

Documentation

The documentation is available on Read the Docs.

There are a few quick examples in the main repository. However, there is also a separate repo containing many more interesting examples that are worth checking out.

License

Flitter is copyright © Jonathan Hogg and licensed under a 2-clause "simplified" BSD license except for the OpenSimplex 2S noise implementation, which is based on code copyright © A. Svensson and licensed under an MIT license.