three.js camera position detection

Question

three.js

When studying the lesson habrahabr.ru/post/224509 , the question arose of how to correctly determine the position of the camera, it is not entirely clear to me how the camera coordinates were determined, can anyone tell me?

camera.position.x = -30;
camera.position.y = 40;
camera.position.z = 30;

Why is the sphere not visible at coordinates? (other elements do not matter, the main principle is to understand)

camera.position.x = 0;
camera.position.y = 0;
camera.position.z = 10;

Answer 1

At these coordinates, you can't see the sphere because it's out of your camera's field of view. When developing a model, if you do not previously control the position of the camera, then you must set the camera to a position from which the modeled object * would be viewed in full. This is what you need to think about at the very beginning. That is, the camera position is set by the developer, depending on the model that we need to get. As far as I can...)