In movie after movie about life after the Alien Invasion or the Devastating Drought or the Worldwide Virus or the Zombie Apocalypse, we have come to expect a certain plot structure and a number of familiar scenes.

• At the beginning of the film, when we meet the scrappy and resourceful survivor(s), the terrible thing has already occurred, and the life they once knew is but a distant, fading dream.

Light of My Life: 2.5 out of 4 CST_ CST_ CST_ CST_ CST_ CST_ CST_ CST_ Saban Films and Paramount Pictures present a film written and directed by Casey Affleck. Rated R (for some violence). Running time: 119 minutes. Opens Friday at Facets Cinematheque.

• It will be a while before we learn exactly what happened. Sometimes we’ll catch a glimpse of a headline in an old newspaper in a dust-covered, long-abandoned convenience store as our heroes hastily stock up on supplies. Eventually we’ll get the full story through flashbacks that include snippets of news broadcasts chronicling the chaos and destruction.

• There will be a number of encounters with strangers — some of them instantly menacing, some seemingly welcoming and friendly. It’s best not to trust anyone.

• Our survivor-heroes will hear rumors and stories about a sanctuary city, or a military base, or a new community, that could be their salvation — if they can somehow survive a long and perilous journey and safely arrive at a place that may or may not exist.

It’s hardly a spoiler alert to reveal writer-director-star Casey Affleck’s post-pandemic, bleak and violent “Light of My Life” contains at least one of the aforementioned elements.

Nothing inherently wrong with that. It’s all about whether the filmmaker finds a fresh and original way to touch on familiar scenarios.

On that count, Affleck falls just short.

Though “Light of My Life” is a well-filmed and occasionally brutally effective piece of work, Affleck dilutes the power of the story with too many self-indulgent, patience-testing scenes.

We start with an overhead shot of Affleck’s character, known only as Dad, curled up next to his 11-year-old child, Rag (Anna Pniowsky), as he spins an elaborate and rambling variation on the story of “Noah’s Ark.”

It’s an intimate, fascinating, initially captivating moment. What is going on here, exactly?

But in the immortal words of Journey, the scene goes on and on and on and on.

This is the first but by no means the last instance in which some judicious editing might have had a positive impact on a scene.

As Dad and Rag navigate a harsh and unforgiving wilderness landscape — living from day to day, taking every measure to avoid contact with other survivors — we get the occasional flashback to some 10 years ago, when an unstoppable virus dubbed “The Female Plague’ was rapidly infecting and killing nearly every female on the planet.

Dad’s wife (Elisabeth Moss), who will soon succumb to the virus, has just given birth. Miraculously, their baby girl shows no symptoms of the plague.

Flash forward a decade, to a world in which only a very few females have survived — which means Dad is in a constant state of high alert, determined to protect his daughter from any and all male predators.

Nearly every day begins with Dad drilling Rag about their plan of escape should they find themselves under attack. (We come to share Rag’s exasperation with these endless drills.)

Dad’s protective measures include disguising Rag as a boy, and introducing her as his son, Alex, to everyone they meet. (Not that he’s being paranoid. In this context, nobody cares about an 11-year-old boy. But the whole world is interested in an 11-year-old girl — and in most cases, for dark and nefarious reasons.)

When Dad and Rag temporarily camp out in an abandoned home, and Rag is excited to find some girls’ clothes that fit, Dad goes ballistic, telling her: “It’s not just a jacket! It’s got sparkling things all over it!”

But for all of Dad’s precautions, it’s becoming increasingly difficult to hide the truth. Perhaps the most impactful and memorable scene in “Light of My Life” features the invaluable character actor Tom Bower as a God-fearing man with a shotgun who sees through the ruse and knows Dad’s traveling companion is a girl. His only concern is the true nature of their relationship.

“Is that your daughter?” he says to Dad, as they watch Rag playing outside.

“That’s my son,” says Dad, weakly.

“What I’m asking you is, is that YOUR daughter?” comes the reply. “Son, I’m asking you to prove it to me.”

In that instant, a man who has spent 10 years doing everything possible to protect his daughter realizes he might not be able to prove she IS his daughter. Affleck and Bower nail this tense, hold-your-breath scene.

Affleck the director and his cinematographer Adam Arkapaw have a keen eye for scene-setting, mood-establishing long shots — and for capturing the essence of a raw and ugly and excruciatingly authentic fight sequence.

There’s much to admire about this film. But for a story set in the future and (to its credit) featuring a strong young female character, “Light of My Life” also has a decidedly retro, patriarchal vibe, with Affleck unable to resist making his character a father-savior comic book hero.

And an attempt to turn the tables late in the game comes across as contrived and cynical. “Light of My Life” fizzles just when it should be achieving maximum explosiveness.