Scene Descriptor

The payload lightd publishes and the LP stand renders. It is a description of what to render, never a frame.

{
  "v": 1,
  "effect": "breathe",
  "speed": 0.4,
  "brightness": 0.8,
  "palette": [
    { "rgb": [232, 77, 0], "weight": 0.5594 },
    { "rgb": [182, 159, 0], "weight": 0.3661 }
  ]
}

Version handling

A scene carrying a different v is refused, not guessed at. A scene that is malformed or unparseable is ignored, and the previously rendering scene keeps running — a stand that goes dark on a bad payload is worse than one that ignores it.

An unknown effect name falls back to solid rather than being refused. A publisher that learns a new effect before the stands do is expected; a lit stand showing the right colors with the wrong animation beats a dark one.

Effects

Deliberately few, because adding one means reflashing every stand.

solid

The dominant color, scaled by brightness.

breathe

The dominant color on a sine, with a floor above zero. A breathing stand that reaches full darkness reads as broken rather than slow.

sweep

Lays the palette out in proportion to the weights, so a color covering 60% of the sleeve covers 60% of the strip, and cross-fades at the seams. Hard edges on a diffused strip look like a fault in the diffuser.

The last two use the accents: the colors of a cover that are not its dominant one.

morph

The whole strip is one color, turning from the dominant color to each accent in turn and back. A color’s turn is half by its weight and half equal, so the dominant color is on longest and a 4% accent is still seen. The end of each turn is a glide into the next. One pass through every color takes two cycles for each color in the palette.

chase

The dominant color fills the strip, and each accent is a soft-edged patch traveling around over it, wider for a larger weight. Alternate accents go opposite ways, so they pass through one another. One lap takes two cycles.

With a palette of one color, both show that color.

scanner

One point of the dominant color going from one end of the strip to the other and back, with what it has just passed fading behind it, and the rest of the strip dark. There and back takes one cycle. Only the first color of the palette is used (ADR-0030).

Speed

speed is a 0..1 dial rather than a frequency so the publisher never has to know what a sensible rate looks like on this hardware. It maps linearly onto a period between 6000 ms (slow) and 1000 ms (fast).