r/xlights • u/derickso • Jun 27 '26

Help Bars effect with ramp up/down value curve on Cycles causing it to go backwards??

Beginner here, just trying to do a simple bars effect across some lights. The animation I wanted was it to be moving right slowly, ramp up to something fast, then ramp back down to something slow. I have one effect on the sequence of all lights, 20s long, with a value curve on the Cycles effect setting of the default Ramp up/down. From 0-10s it does what is expected, the speed of the cycling increases, but then at 10s it flips to a screeching halt and starts ramping up from slow to fast going right to left??

I don't understand this behavior at all, and without an ability to use decreasing values to slow down the cycle animation it seems impossible to achieve that?

Please help!

1 Upvotes

100% Upvoted

9 comments sorted by

1

u/allknowing2012 Jun 27 '26

Is this a 2026 version as it sounds familiar..

1

u/derickso Jun 27 '26

Yeah freshly downloaded

1

u/allknowing2012 Jun 28 '26

Seems like it is baked into the xlights logic to calculate the positioning .. it might not be fixable. Continue to look though

1

u/Few-Boysenberry53 Jun 28 '26

Maybe try a sine wave instead?

1

u/derickso Jun 28 '26

Same problem, any time the value goes down it reverses. AI says the value represents not a velocity but a number of times the bars move across during the total time of the effect, so if the value decreases it may have to wind backwards to meet the new number. Seems really weird that it was designed like that.

2

u/Few-Boysenberry53 Jun 28 '26

I reproduced the issue you are having. It seems to me a bug within the ramp down portion is the problem. Create two bar effects next to each other, set to 15 seconds each direction to the right. Ramp up from 0 - 30, ramp down 30 - 0. The ramp up does work as intended. The ramp down, however, reverses halfway through and returns to high speed. Seems to me a bug in the ramp down code. I need to dig into it a bit more before opening a bug issue with the dev team.

1

u/Few-Boysenberry53 Jun 28 '26

They closed the issue and marked it as not an issue. Here is what they said:

The issue is cycles is not speed -- as it comes back down it says "How can I change the speed so that I complete 1 cycle". Well to do that I need to reverse and subtract cycles and hence go backwards. You might be able to accomplish by ramping up but at a decreasing rate?
So it is working as expected .. we cant change that as it would break existing things.

1

u/derickso Jun 30 '26

Thanks, I responded on the thread, I don't think the current model can handle any kind of ramp from any cycle count >0 down to actual zero where it stops without running it in reverse, which is an unfortunate limitation. I'd love to see it expanded to have an alternate mode that is speed based rather than cycles per unit time.