Hi @Radek_HART, sorry for the delay.
I had trouble finding the correct way of dealing with this. Adding a post process effect to a camera, automatically creates a new layer (PostEffectQueue) with a render target, that’s where the post effect is rendered to.
It seems there is no need to create and assign a render target, but we can use and read from that layer render target. So I thought, and that solved the blank texture issue, but the rendered result doesn’t include, mysteriously, the post process effect.
var colorBuffer = this.cameraEntity.camera.postEffects._sourceTarget._colorBuffer;
Try submitting an issue about it in the engine repo, either it’s a bug or there is another way of doing this.