Bringing in a single texture with a callback is a simple task, for instance:
var loader = new THREE.TextureLoader();
var texture1 = loader.load("https://i.imgur.com/UiTMJzv.png", process);
//executed only once texture1 is loaded
function process(){
}
But how do I go about loading multiple textures asynchronously (and not one after the other) and make sure a processing function is only triggered once all textures have finished loading?