Its a modification of the LED control to make them simulate the look of bulbs-
LEDs turn on instantly, bulbs ramp up and down.  Pulse width modulation difference.

On the Pi Zero not being able to do it...
Ah the Pi Zero being single core has a performance disadvantage which right now
restricts it.  I caught a thread on the forum saying they are considering hardware pulse width
modification which would side step the performance issues.

On 12/28/2016 05:05 PM, william degnan via vcf-midatlantic wrote:

sorry "bulb-effect" lighting mod

What is this, I'm not finding info on this. I haven't really dug in too
deep on the PiDP.