_setLoaderSize(size) {
        this.sourcesToLoad = size;

        if(this.sourcesToLoad === 0) {
            this.complete = true;
            this.renderer.nextRender.add(() => this.onComplete && this.onComplete());
        }
    }
Sets the total number of assets to load before firing the onComplete event

     params:
     @size (int): our curtains object OR our curtains renderer object
*