i am very beginner with Babylon (i was event dont know it a week a go).
i have s simple test with arc rotate cameras setup (two cameras), tree buttons to trigger somes effects, one mesh, and, one scene onPointerObservable event for outline the picked mesh.
With one camera active the effects and the picked mesh work works, but the buttons get affected by the effects (very visible with sharpen effect).
With two cameras active (one for the entire scene and one for the ui) the effects works, and buttons are not affected by the effects, but the piked mesh dont work anymore.
So, for try it, just swich the comment on lines 41 and 132, 133 to swith from one to two cameras.