How to reverse direction of firework rocket sparks

Patterns and Code
1

Im trying to figure out how to reverse the direction of the rockets and sparks on the strip.

I imagine its easy if you know, but i cant figure it out.

any help would be appreciated.

Thanks,
P-Dog

2

Hi and welcome!
The easiest way to reverse the direction of this pattern is to virtually reverse the direction of the LED strip.

To do this, just add the a line like the following as the first line of the render() function when you want to go the other way:
index = -1+pixelCount-index

How this works:
In render(), index is the number of the current pixel. Normally, this runs from 0 to pixelCount-1.
We “flip the strip” by subtracting the “real” index from pixelCount so that it runs from pixelCount-1 to start. Once we’ve done this reversal, we don’t have to touch the rest of the pattern math at all.

Here’s a version of the pattern equipped with a slider that lets you control direction from the UI:

var dir = 0

export function beforeRender(delta) {
  t1 = time(.05)
  t2 = time(0.0001) * 0.2
}

export function sliderDirection(d) {
  dir = d >= 0.5;
}

export function render(index) {
  if (dir) index = -1+pixelCount-index
  v = wave(t1 + index/pixelCount)
  v2 = wave(t1 + (index+10)/pixelCount)
  s = (v2 < 0.9995)
  v = (v > .95 && random(1) > .95) * v
  h = random(1)
  h = (s ? h : (index/20)%.2)
  hsv(h, 1-s, (1-s) + v )
}
2 Likes
3

Appreciate you taking the time to answer.

I will try it out.

Thanks Again,

P-Dog

4

Switch to the toggle controls (introduced in v3.24 and v2.29) and you get a nice switch!

export function toggleDirection(d) {
  dir = d
}

It all comes down to the magic (key)word used :slight_smile:

1 Like
5

That did work great,
Thank you so much for your time!

1 Like