There is a moment in the movie “MASH” that you’ll miss if you blink: Major Houlihan and Lt. Col. Blake are facing the camera and staring into the far-off distance. They are clearly looking and waiting for something, and then we hear the sounds of a helicopter approaching. As the sound gets quite loud, Blake and Houlihan realize, with a start, that they have been looking in the wrong direction and the helicopter lands right behind them.

It’s a perfectly realized moment among many in the more than 45 films directed by Robert Altman during a career that, for all intents and purposes, began in 1968 (with a sci-fi moonshot adventure called “Countdown”). Altman died last week at 81, just as he was preparing a new film. He had been ill, but since Altman never seemed to quit, the news was a jolt. As many times as we took the next Altman film for granted, it is quite a shock to realize there will be no more.

Here are a few more moments: the scene in which the butler, played by Alan Bates, in “Gosford Park” cleans a knife by spitting on it—what could be more cruelly contemptuous to his employers? Or Elliott Gould’s monologue, seemingly delivered to his cat, at the beginning of “The Long Goodbye.”

Not everything was successful (1979’s “Quintet” with Paul Newman was dreadful), or as bad as people thought (1980’s “Popeye,” with a sweet, classic score by Harry Nilsson); and some were much better than some recall (Altman’s little-remembered 1988 TV version of “The Caine Mutiny” is a stunning film by any standard).

But that one moment in “MASH” (1970) seems particularly emblematic of an Altman film, a delicately realized detail that comes at you from a completely unexpected direction. Altman’s films were stuffed with them. String those moments together, beginning with “Brewster McCloud” (1970) to “A Prairie Home Companion” (2006), and you have one of the richest bodies of work by any director who has ever worked in American film.