Apologies if this has been discussed before. I couldn't find exactly what I needed in the existing topics.
I'm not great at expressions, so I have trouble wrapping my mind around an example that isn't exactly what I need.
So, basically, I have a set of layers (say 20), all identical, arranged on the comp. I want these to randomly turn on and off at 20 frame intervals. BUT I don't want it to be too random. At every interval, I want some layers to dim to 50% opacity (off) and some to stay at 100% (on), then a half second later, some go up to 100% and some to 50%. I want the transition itself to last 10 frames. So each cycle would be 30 frames. I don't want any to land on random values between 50 and 100 and I don't want it to look jerky. I'm going for a smooth transition every 20 frames. So I guess the only thing that is really randomized is which layers change at each interval. Does that make sense?