Value variation.

Today we'll look at a very simple way to generate a ‘random’ value. Of course it's not truely random, but it does the job for an artist sake.

What will happen if you plug a constant as your texture coordinates?
Every single pixel of your constant has the same value so they're all going to go pick the same pixel. That means that you'll get a constant value as an output as well.

If you're after a flicker, simply add a panner in the middle. You'll move the texture around so the value of the pixel in the centre will be different over time, and you get a fluctuating value. You wanna pan in both U and V to avoid repetitive patterns.

 

The rhythm of a malfunctioning neon light could be something like this:

(The texture is simply the inverted cell pattern effect from the after effects with some levels to darken it. )

If you want some mad flicker, use a very contrasted texture and pan it faster.
If you want some very soft variations, use some very soft gradients that you'll pan slowly.

Unfortunately, I haven't been able to record any of this because the framerate issues make it useless.