EffectComposer/Transmission: Using scene.background with a texture and having an EffectComposer breaks transmission rendering

[hybridherbst]

Description

It looks like there's a depth clear issue (?) when using a scene background together with EffectComposer when transmissive objects are rendered.

The result is that only the background is visible in transmission, not the scene content. Sometimes parts of the scene content are visible but then "disappear" (thus my assumption that this is related to some depth buffer not being cleared correctly).

Reproduction steps

1. Go to https://jsfiddle.net/0zLhsk3u/103/
2. Rotate the camera a bit (first frame likely works because depth buffer is empty before!)
3. Note that the grey object is not visible in the transmission
   .
4. Press "F" which will switch from a background texture to a background color.
5. Note that the dark green sphere is visible in transmission again.
   .
6. Press "F" again to switch to background texture again (dark green sphere disappears from transmission)
7. Press "C to disable the EffectComposer
8. Note that the dark green sphere is visible again

So this combination breaks:

• Background texture + EffectComposer + Transmission

Code

See https://jsfiddle.net/0zLhsk3u/103/

Live example

https://jsfiddle.net/0zLhsk3u/103/

Version

r167dev

[Mugen87]

This is a regression since the demo works up to r164: https://jsfiddle.net/Lrvkd0s1/

It starts breaking with r165 which contains a fix for another transmission issue: #28420

Maybe the fix has a side effect that is the root cause for this issue.

[Mugen87]

The PR #28434 fixed an issue in context of color spaces in r165. #28447 tried to optimized the code but introudced this regression. I'll revert the PR.

[hybridherbst]

Thank you!