Fascination with Heath Ledger no doubt swells the mobs going to see “The Dark Knight,” the new Batman movie. Ledger’s brilliance as the psycho Joker has spawned speculation that the actor’s own descent into drug madness had fueled his demonic performance.

Ledger died of an apparently accidental prescription-drug overdose last January, just as the main filming ended. The 28-year-old actor’s death shocked the public.

There was no surprise in the passing last week of Randy Pausch. For almost a year, the 47-year-old professor of computer science had been confronting terminal pancreatic cancer.

Pausch felt well for much of the time. Also movie-star handsome, he put those golden months to good use, reflecting on life and the final business of life.

Pittsburgh’s Carnegie Mellon University periodically asks its professors to prepare a “Last Lecture.” Because of his diagnosis, Pausch’s “last lecture” was to be truly that.

Pausch had assumed that only a few students would show up. News of his condition helped pack the hall. Delivered with humor, passion and not a shred of self-pity, the lecture became a Web sensation. Big media feted Pausch with celebrity and honors.

What did Pausch say? He started off with a slide of a CT scan showing his tumors, then pretty much dropped the subject of cancer. He urged the students to reconsider their goals, and once they landed on their ambitions, to sidestep their failures. “Brick walls are there for a reason,” he said. “They let us prove how badly we want things.”

His personal grief wasn’t over the prospect of not seeing his three young children grow up, but in knowing that they would grow up without their father. Pausch didn’t have 30 years to impart his wisdom to them. He had to do it right away.

Pausch looks the picture of health in “The Last Lecture” video. He does one-armed pushups and ribs the students, “I’m in better shape than most of you.”

It’s a bit of a shame that the story has been turned into an inspirational tear-jerker. The lecture is a monster hit on YouTube, and his book, “The Last Lecture,” co-written by Jeffrey Zaslow, dominates sales in the self-help aisles. Such lines as his vow to have fun every day left “because there’s no other way to play it” can have a maudlin ring.

Pausch’s biography should include his considerable achievements as an innovator in the teaching of computer science. His programs helped students gain sophisticated computer skills by developing their own games.

Pausch ended his days in character as a professorial analyst. Ledger was literally in character, as an actor filling the Joker with manic evil. But while each man was master of his craft, their ends couldn’t have been more different.

Ledger’s death, while self-induced, was surely not in his plan. Pausch had the benefit, or perhaps agony, of foreseeing his shortened future. He understood there was no way to change his abbreviated storyline. That he played it so well will be his own legacy.