Overview

The CURIO LED runs small Lua scripts. You write one in the browser, press Upload, and it is drawing on the LEDs a moment later. These pages start with a first script and end with how the panel’s shader compiler and virtual machine work inside.

Where to start

If you want to	Read
Get something on the panel in five minutes	Your first script
Try a script without a panel	The preview
Understand what a script is and how it runs	How a script runs
Draw shapes and move them	Drawing, then Animation and uniforms
Colour every pixel with a formula	Fragment shaders
Make a shader run at full frame rate	Interpreted and compiled
Draw lit, textured 3D	3D
Look something up	API reference, Shader built-ins, Limits
Know how it works underneath	From source to pixels, The bytecode, The shader VM

The short version

A script is plain Lua 5.4 with three optional functions the panel calls for you:

function _init()        -- once, when the script starts
end

function _update(dt)    -- every frame; dt is seconds since the last frame
end

function _draw()        -- every frame, after _update
  gfx.cls(0, 0, 40)
  gfx.pset(32, 32, 255, 255, 255)
end

There are three ways to put pixels on the panel, and you can mix them in one script:

• Drawing calls such as gfx.pset, gfx.rectfill and gfx.line. Simple and fast for shapes and sprites.
• A fragment shader: one function, fragment(x, y, u), that returns the colour of a pixel. The panel calls it for every pixel, or runs a compiled version of it several times faster.
• 3D meshes drawn through a built-in pipeline with a camera, lights and textures.

The panel is 64 pixels wide and 64 high. Everything on these pages uses gfx.width() and gfx.height() rather than assuming that.