Three.js postprocessing without affecting scene background

I feel like I’m overthinking this.

How can I apply postprocessing effects to my three.js scene without affecting the scene background texture?

For context, I am building a WebAR experience with 8th Wall. I can render the camera texture behind the three.js scene by setting scene.background = camTexture but when I use composer.render() instead of renderer.render(), the postprocessing effects are applied to both the three.js scene and to the scene background. I just want to apply the effects to three.js scene and leave the scene background as-is.

Btw, I don’t even need to set scene.background = camTexture unless I am using EffectComposer(). By default the three.js scene has a transparent background and the cameraTexture is rendered behind the three.js scene. But the minute I use EffectComposer, it shows a solid white background instead of staying transparent, which is why I set scene.background = camTexture.

I would greatly appreciate any suggestions!

Do you mind demonstrating with a small live example what goes wrong? Using EffectComposer with a transparent background should work in principle. It’s just important to use a clear alpha value of 0.