Latest build 6.38.1 got glitchy opacity animations

[VanderSP]

Description of the bug

Animate opacity fadein/fadeout, it glitches black all around

To reproduce

I believe just animate? im using alpha canvas above another canvas

Expected behavior

Stable fade as below 6.38.1

Library versions used

• Three: tested from 178 to 182, actually in 182
• Post Processing: 6.38.1

Mobile

• Device: Tablet Lenovo
• OS: Android 12
• Browser Webview/Chromium

[vanruesc]

Hi, thanks for the report.

Can you please provide a minimal reproduction of the issue? I'm unable to reproduce it based on the information in this ticket.

[VanderSP]

Lol, I also tried to reproduce in some kind of claude sandbox, and I still not figured out how to simulate it... but i can RECORD A MOVIE lol... later I wll try more.

[VanderSP]

Sorry, I checked again it´s on the latest version the bug was introduced!

At least, less culprits!

[VanderSP]

Used antigravity to isolate the bug... found the culprit!

Bug analysis:

I managed to isolate the issue. It seems related to how EffectPass handles screen output in the new version (6.38.1), specifically regarding alpha/transparency blending or color space conversion when rendering to the default framebuffer.

Findings:

The Glitch: Occurs when EffectPass is the final pass in the composer chain (rendering directly to screen).
The Fix: Adding a manual CopyPass (or ShaderPass(new CopyMaterial())) after the EffectPass solves the issue perfectly.
Isolation: I verified that the library's standard CopyMaterial is working correctly (since the manual pass uses it without issues).
Conclusion: The regression appears to be in the specific logic EffectPass uses when it writes to the screen (last pass). When forced to write to an intermediate buffer (by adding a subsequent pass), the output is correct. The issue only manifests when EffectPass blends directly to the screen.

Workaround: Added a final pass to bypass EffectPass screen output:

// Bypass EffectPass screen output glitches in 6.38.1
composer.addPass(new ShaderPass(new CopyMaterial()));

[vanruesc]

Thanks, that helps a lot 👍

I changed the behavior of the EffectPass in 6.38.1 to use NormalBlending with tranparent set to true on the EffectMaterial in hopes that this would help fix #475, but alas.

I'll revert that change tomorrow and publish a new release after some more testing.

[vanruesc]

Should be fixed in v6.38.2.

[VanderSP]

Installed, can confirm it fixed!

Thanks!!!