Event Background: Transitions with fade time cause scene background to bleed in

[Pheubel]

The problem

Describe the bug
When you have a background A and switch to background B with a fade time larger than 0, you can see the scene colors, what is behind the backgrounds, blend in. This makes it hard to make transitions look right.

To Reproduce
Steps to reproduce the behavior:

1. In Project > Project Settings > General > Rendering > Environment set the default color to something noticeable, like bright red.
2. Create a timeline
3. Add a background event
4. Create another background event
5. Set the fade time of the second background event to 1 second
6. Play the timeline

Expected behavior
The two background should blend into each other without the scene bleeding into the view.

Screenshots

When switching backgrounds you can clearly see the red color from the default scene environment bleed into the view.

System (please complete the following information):

• OS: Windows
• Godot Version: 4.1.1
• Dialogic Version: 2.0 - Alpha 10

Solutions

Workaround

Not really dialogic, but what i did in my own project i had a need for a similar transition system, for that I use of the image scene A produced and scene B produced and inserted it into a shader and it then lerps the colors of both scene images. It then put's the result on top of both scenes as a sort of overlay in a color rect that hides the scenes behind it. When the transition is over, the overlay is hidden again.

Possible fixes

I think that the issue stems from the fact that the backgrounds try to become transparent, rather than each other. With how transparency works this can cause some bleeding through of things behind the images to pop up

Since you have two backgrounds that go between white (indicates that the background is fully visible) and transparent (background not visible).

One way to go about it is to change how backgrounds get transitioned into each other would be change the system with something similar described in #1826 (comment). In order to get a simple fade transition you could use a full mid gray texture and set the feather to 1, this will fade the entire image at once close to how it's currently done out of the box (minus the bleeding).

A concern with it however is the scale of the backwards compatibility break. I haven't done much research yet, but some points that should be looked at are:

• change in scene structure - it could be that in order to get it to work nicely a change in the scene's structure has to be made, making user made scene possibly incompatible.
• the role of fade_in() and fade_out() - if the transitions are handled differently for the custom scene using these functions they most likely aren't going to work so well. Their use in the current eco system might need to be investigated.