Noob guide to creating "mirrored" patterns in single string of WS2811?

Patterns and Code
1

What is the key to creating a “mirrored” pattern in PB - one that is symmetrical on either side of the center of the string? I see that there are several posted in the Patterns listings, and the centerpoint would be easy to find but how do you create a pattern that is “reflected” as these are? I think I’m missing something that’s obvious…

2

Basically, in your render() function, you do the same thing for each half of the LED strip, but the second half is mathematically reversed.

Here’s the simplest example I can come up with. The first and last pixels should be off, and the middle two pixels will be full-on. I assigned different colors to the two cases so you can see which is which.

middle = floor(pixelCount/2) - 1

export function render(index) {
  if(index <= middle) {
    value = index / middle // a number [0..1]
    hue = 0 // red
  } else {
    value = (index - middle - 1) / (pixelCount - middle) // a number [1..0]
    hue = 0.5 // cyan
  }

  hsv(hue,1,value)
}

Of course I haven’t tested it but I think I got all the fencepost logic in the right place!

1 Like
3

Thanks for this!

I’ve done some mapping that’s very similar using Arduino platforms and I think my hangup with Pixelblaze has been assuming that using particular pixel/LED involves “chaining” it all the way up the string - with the command being rendered and the LED showing as it goes - rather than being effectively rendered/shown just once as the data arrives at the target LED.

On to other errors…

Thanks again