How can I create this "Chase/Fill" effect?

[szaske]

I created some sequences in HLS and imported them into xLights. In this example my "model" is a string of 18 Icicle lights. Each icicle is 8 pixels and the whole string is 144 pixels long.  Attached is what the sequence looks like after importing it. You can see nodes 1 - 8 is icicle #1 and colored green. Icicle #2 is node 9-16 and colored red.  The effect I'm trying to achieve is pretty simple, I want the icicle to "fill" from nothing or black to all 8 pixels colored green. This fill effect should happen over an amount of time, say 3 seconds. Can someone explain how I can achieve this? xLights has a ton of effect types but I'm struggling to find ones for simple scenarios like this one. The effect works if I hand edit each node but I know xLights does not really want us editing each pixel, so I'm hoping there's some way to replicate this effect.

[dkulp]

Something "similar" can be done with two layers....   

The bottom layer would have a "Single Strand" effect using the Skips.   Colors set to Red/Green, skip size 0.   This gets the icicles to have the red/green alternating pattern.

The top layer would use a Curtain effect. Curtain Edge Top, Effect Open, Swag Width 0.   Use color of white and set to "1 is Unmask".    You can try adding some "blur" to the Curtain to smooth the edge a bit. 

There are other ways as well.  The curtain could be replaced with a morph.   Likely could be replaced with a second single strand effect rotated 90degrees with persistent turned on.