Pixelblaze, Advance One Pixel at a Time

pixelblaze_advance_one_pixel_at_a_time.js

var holdMs = 120          // milliseconds each LED stays on (lower = faster)
var currentPixel = 0      // index of the currently lit pixel
var accumulatedMs = 0     // accumulated elapsed time (in milliseconds)

// A beforeRender fuction runs before each frame or refresh of all LEDs
export function beforeRender(delta) {   // delta = ms since last frame (refresh of all LEDs)
  accumulatedMs += delta                // add this frame's time to the accumulator

  // If we've held long enough, advance to the next pixel.
  // NOTE: This advances at most one pixel per frame.
  // For perfect catch-up on slow frames, replace `if` with a `while`.
  if (accumulatedMs >= holdMs) {
    accumulatedMs -= holdMs             // keep leftover time for the next step
    currentPixel = (currentPixel + 1) % pixelCount  // wrap to 0 at the end
  }
}

export function render(index) {
  // Light only the current pixel. In Pixelblaze, (index == currentPixel)
  // is a boolean that casts to 1 (true) or 0 (false), used here as V.
  // Hue 0.02 ≈ orange-red, saturation 1 = pure color.
  hsv(0.02, 1, index == currentPixel)
}