First, Point of View is kind of like a camera. Should you choose first person or third-person limited as your POV, then you, as the writer, are holding the camera and looking at everything as if you are that character. You're doing the observing, the interacting. If someone other than your POV character is suddenly doing the interacting, the observing, the actions, then you have "broken" POV. This is perfectly acceptable when you switch scenes, to have one scene in one POV and another in another. Of course, everything is acceptable if it works. But generally, you would only have one POV per scene if you're writing third-person limited or first person.
If you choose second person or omniscient, then you are still holding the camera, but you're not inside the character. You're waaay above the character, outside of them, watching everything from an external position. Viewpoint as filter is something you can use in first or third-person limited. If you are writing in second person or omniscient, another type of focal point is needed, such as theme. Often, omniscient novels are a sort of group pov where the author switches between points of view extremely often.
You know you've broken POV (in first and third-limited) when you step away from the camera, outside of things you cannot see or know.
VIEWPOINT AS FILTER
This is a technique that can be used in third-person limited as well as first person.
When I was first learning some intermediate things in writing, I came upon a book called The Marshall Plan for Novel Writing by Evan Marshall. And he has a section in this book that really helped me to understand viewpoint writing. This is what he said:
Viewpoint writing makes all the decisions for you. Your viewpoint character is walking in a garden and sees some purple flowers. Should you give their name? If the viewpoint character knows their name, yes. If not, no; you would simply write something like:
"Masses of purple trumpetlike flowers crowded over the edge of the path."
Later, he says:
When you use viewpoint writing, your reader knows only what the character knows or is aware of at any given moment....
Whenever you're in doubt about what or how much to show at any given point, turn the question over to viewpoint writing. Would you describe your viewpoint character's appearance? Viewpoint writing says you wouldn't do so from that character's viewpoint, unless the character would have a specific reason to think about his own appearance....