If you look closely at one of Thornton Willis’s paintings at Elizabeth Harris Gallery, you might see a sailboat transform into a kite. Or is it a kite metamorphosing into the sharp fins of an origami fish? Yes, maybe it is a fish disappearing under the weight of a lopsided skyscraper tumbling over into a rainbow-colored sea of triangles. This is Mr. Willis’s jumbled geometric art.

The artist, a Florida-born New York abstract expressionist, is about to conclude his first solo exhibit since 1993, demonstrating to the art world that it’s possible to bounce back from obscurity at the age of 70. Mr. Willis, whose work has made its way into the permanent collections of the Whitney, the Guggenheim, and the Museum of Modern Art, among others, is hardly a household name these days. But he was a darling of the New York art scene during the 1980s — prominently featured in top industry publications such as Art News and Art in America — and his paintings were exhibited widely throughout this country and Europe.

Best known for what became his trademark in the 1970s — huge, vibrantly hued canvases dominated by a single iconic wedge of color — Mr. Willis abandoned that motif long ago and has been toiling away on his triangular compositions virtually in the shadows for the past dozen years.

“It’s nice that he’s having a real comeback because it doesn’t often happen in the art world,”the founder of the gallery where Mr. Willis’s newest show is being exhibited, Elizabeth Harris, said.”It’s as youth-obsessed as Hollywood.”

Mr. Willis’s return shows that all he needed was dogged perseverance and a little inspiration from quantum mechanics.

“I’ve been reading physics books,” the silver-haired Mr. Willis told The New York Sun in the Pensacola accent he’s managed to retain even after 30 years of living in Manhattan.”We know that there’s no such thing as empty space. What we see as solid matter is only an illusion. And I think that’s influencing my work.”

Described by some of his friends as a soulful Johnny Cash type, the painter looks professorial instead, in his largeframe eyeglasses, his leg twitching with nervous energy as he sits in his art-filled SoHo studio, enthusiastically discussing his new approach to his art. “I used to be concerned about positive and negative, figure and ground,” he adds. “I am no longer concerned about those things.”

Mr. Willis’s latest work — abstract, painterly odes to the three-sided figure — have the raw appeal of optical illusions, and their strident configurations of overlapping shapes have a quality that transcends two dimensions, at times seeming to recede into the canvas, or alternately, to jut outward as if to touch the viewer. Although the artist denies his compositions are intentional representations of any kind, half-perceived images often seem to appear and disappear in the impossible cubist-inspired geometries of his paintings, as clouds on a windy day can seem to take on the contours of people and everyday objects.

These works, though, some of the most striking of his career, are a marked departure from his earlier efforts, and he has paid a price for his abandonment of the wedge for which he is known.

“People told him never to stop painting like that,” Mr. Willis’s wife, Vered Lieb, told the Sun. “He said, ‘How can I do that? I need to keep growing.’ But there is a lot of pressure in the art world to keep doing what made you famous.”

However, after 13 years devoted to the wedge, Mr. Willis found his muse pulling him in a different direction. After all, how could an artist be expected to devote an entire career to a single motif? Privately, however, that is exactly what his colleagues counseled Mr. Willis to do.

In a moment of self-doubt during that period, the artist said he called a friend, the minimalist sculptor Richard Serra, and asked what he should do next. Mr. Serra’s advice: “‘Just keeping doing the same thing, Thornton. Just keep doing the same thing.'”

But if doing the same thing meant painting more wedges, then that was something Mr. Willis said he could not bring himself to do.

“I wanted to make a more dynamic painting,” Mr. Willis said. Yet making the choice to follow that new inspiration, despite the warnings, “did take courage, I have to admit,” he said.

So in the early 1990s, after a brief flirtation with zigzags, the painter embarked on his ongoing odyssey with color-drenched three-pointed figures.

Ms. Harris, who has known Mr. Willis since 1979, said what distinguishes the artist from many of his more well-known contemporaries is his unique purity of purpose. What matters most to Mr. Willis, she said, is creating art, not promoting himself.

“He seems passionate about the work, but he doesn’t seem that concerned about a career,” she added.

That kind of sincerity is also what stands out about Mr. Willis for the Irishborn abstract painter, Sean Scully, who was an acquaintance during the early 1980s. Mr. Scully said he sees genuineness and innocence in Mr. Willis’s personality as well as his paintings.

Mr. Willis “has a kind of modest, unassuming openness, and that has allowed him not to become cynical,” Mr. Scully told the Sun. “There’s almost a naïveté in the way he paints.”

For his part, Mr. Willis doesn’t rue the consequences of prioritizing his artistic growth over his name recognition. If he had not done so, he points out, his new quantum-inspired art would never have been created.

“Look, there’s politics in the art world. I don’t have any bitterness,” he said. “What success is about is keeping on doing it. I’m in the best position I’ve ever been in my life.”