How to check when the game has started?

It there,
I noticed that when a project starts (in HTML5) you will get right before any 3d objects are rendered a very brief black flash popping before the game starts.
I checked various way with gl canvas background color, or making the all canvas transparent and there is no easy fix for this.
I would like to try to add a picture on top of everything until the game starts.
Is there a global variable or something that we can check that confirms that the game has started and all objects have been rendered?

Hi. I’m not sure if a loading screen checks if the whole scene is entirely rendered first, but perhaps a loading screen is what you’re looking for.

Preview the demo:

Download the demo:

The loading screen loads elements then the scene starts.
What I am trying to check is that the scene has been correctly rendered once started.
I played with this function :
but it does not seems to work correctly on HTML5