# BUG: transition timeline interacts with destination fade-in

**URL:** <https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228>\
**Category:** FMOD Studio\
**Created:** [May 20, 2021, 2:02am UTC](https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228 "2021-05-20T02:02:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Alcibiade](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/alcibiade/32/4284_2.png) [@Alcibiade](https://qa.fmod.com/u/Alcibiade)\
**Post date:** [May 20, 2021, 2:02am UTC](https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228/1 "2021-05-20T02:02:47Z")

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When the destination has a micro-fade-in in the main timeline, after a transition timeline, it behaves strangely, as if the fade-in were longer (even though the transition timeline doesn’t have fades at all).

> **[Bug transition fade.fspackage](https://drive.google.com/file/d/1BBVBf7NiKjqfdMzLMYvBhmpD89orKtYe/view?usp=sharing)**
>
> Google Drive file.

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**Author:** ![tristanjl](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/tristanjl/32/261_2.png) [@tristanjl](https://qa.fmod.com/u/tristanjl)\
**Post date:** [May 20, 2021, 6:17am UTC](https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228/2 "2021-05-20T06:17:07Z")

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Hey Alcibiade,

The behaviour does seem odd, however, it is actually the intended behaviour, but the reasoning does require a little explanation.

With transition timelines, we interpolate the values of all automation and fade curves. We take the value where you transition from and at the destination and we move from one to the other over the length of the transition timeline. This means that you will avoid having any unintended jumps in automation/fade curves that are on the main timeline through a transition, but it does mean that fade curves and automation will be more smoothed out than you would otherwise expect.

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<div class="post-metadata">

**Author:** ![Alcibiade](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/alcibiade/32/4284_2.png) [@Alcibiade](https://qa.fmod.com/u/Alcibiade)\
**Post date:** [May 20, 2021, 7:43am UTC](https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228/3 "2021-05-20T07:43:36Z")

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That’s odd indeed! What’s the benefit of this behavior, instead of simply summing all automations/fades?  
Here’s a video, for the ones wondering what we’re talking about:

[![](https://img.youtube.com/vi/HkVbGz_Rl9Q/hqdefault.jpg "FMOD transition fade odd behavior") ](https://www.youtube.com/watch?v=HkVbGz_Rl9Q)

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<div class="post-metadata">

**Author:** ![tristanjl](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/tristanjl/32/261_2.png) [@tristanjl](https://qa.fmod.com/u/tristanjl)\
**Post date:** [May 20, 2021, 11:20pm UTC](https://qa.fmod.com/t/bug-transition-timeline-interacts-with-destination-fade-in/17228/4 "2021-05-20T23:20:48Z")

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Digging into this further - I think you are right, and we should change this for instrument fade curves. We actually already have a task in our backlog to improve this which I had forgotten about.

This is a bit of a tangent, but automation curves are a bit different - you can edit them for the transition timeline, and if unedited, you have two values to draw from (source and destination), which could be overlapping, so a simple lerp makes the most sense.

Fade curves currently share an implementation with automation, so we would need to separate them to have fade curves work better with transition timelines.