Help with WS2801 LED Strand -- Random Fade In & Out

Other Hardware LEDs and Multiplexing
1

Hi Guys,
It has been decades since I've touched code. I'm working on a project using an Arduino and a WS2801 RGB LED strand with 20 pixels.

I want to fade in and out (from off to full white bright the off) at random a population of LED in the strand of 20.

Here's an example of what the effect I'm trying to accomplish. VIDEO . He calls them splotches.

I can fade in and out a certain LED, but I'm trying to get pseudo code for the random activation LEDs.

Any ideas would be greatly appreciated.

2

An explanation what has to happen + FastLED code making it happen can be found here.

Long story short: somewhere you need to store a flag for each led indicating if the led is brightening or diming at the moment.

Depending on the flag you brighten or dim each led. If you reach the upper/lower limit (=led full on / off) you inverse the flag.