It is fortuitous that a show of the Abstract Expressionist sculptor Tony Smith's "Louisenberg" paintings from 1953-55 is on view at the same time as the "Leonardo da Vinci: Master Draftsman" exhibition at the Metropolitan Museum. Though separated by almost half a millennium, both artists sought to expand the parameters of their profession, from architecture (engineering, in Leonardo's case) to large-scale sculpture, in addition to battling with the vicissitudes of painting. Both artists took on major commissions and struggled to realize their visions, moving feverishly from one medium or discipline to another.

What's more, the two artists shared an aspiration for ideal form and a unity of material and idea. During the Renaissance, of course, it was not that unusual for an artist to be versed in all the plastic arts. Smith was trained as both artist and architect, and practiced each with distinction for much of his creative life, the conceptual flow from one medium to another clearly observable over three decades of work.

As an artist, Smith's métier was ultimately sculptural in nature. His ideas were best realized in real space as cubic forms, polygons and tetrahedrons, extended into larger, more complex inventions. His massive, 17-foot-tall sculpture Moondog (1964), exhibited at the Paula Cooper Gallery in Chelsea in 1997, energized the space it inhabited in such a way that this three-legged creature could barely be contained within it. Wherever one confronts them, Smith's sculptures are dramatic and unexpected, bringing a structural simplicity to the most mystifying of geometric configurations.

The paintings and works on paper in "Louisenberg" at Mitchell-Innes & Nash are in many ways the two-dimensional explorations of a sculptor, regardless of how utterly flat his eccentric, organic shapes appear to be on the picture plane. The formal conception of these paintings is geometric; circles within a squared grid that double and quadruple, expanding and jockeying for position in a tightly configured space.

The larger, more complex works in the Louisenberg series suggest, all at once, architectural, sculptural and (somewhat harder to define) painted space. The exhibition itself, with its working drawings and smaller oil studies and one mural-sized painting (executed in 1968 under the artist's supervision), offers a valuable opportunity to examine the development of Smith's compositional strategies in various stages of realization.

Along one wall of diagrammatic pencil and ink sketches is a single study that is the mathematical key to the paintings. Carefully done in ink on graph paper, this drawing shows the systemic approach Smith took to the series, which is named after a geological site near Bayreuth, Germany. (The title has a certain personal resonance as well, for in 1953 Smith left his Ab-Ex friends behind in New York and joined his wife Jane, an opera singer, in Nuremberg.)

In this study of 25 concise rectangles and squares, each identified with a letter of the alphabet, Smith mapped out the alignments of circles and multiple circular units that would make up the Louisenberg series. Referred to as "peanuts and architectural quatrefoils" in Robert Storr's catalogue essay, these forms appear to be conjoining or splitting apart at the same time. Resembling cells in the process of meiosis or mitosis, these mutating, elemental shapes spawn arrangements that seem in constant flux, in contradiction to their static appearance.

Somewhere in between Rothko's hovering mist and Newman's emaciated zips are Smith's embryonic cells, more concrete than the former, more grounded than the latter; just what you might expect of an artist who thinks in terms of geometry and mass.

Clearly, Smith intended the Louisenberg works to be seen as a whole, and in fact it is easier to grasp the artist's process, from conception to execution, when seeing these works all together. Storr points out here, as he did to a greater extent in his essay for the exhibition of the artist's work he organized at the Museum of Modern Art in 1998, that Smith's self-imposed exile from the camaraderie and distractions of the New York art scene of the '50s made it possible for him to make a radical leap in his work.

Having completed a group of architectural projects, Smith turned again to painting. With the Louisenberg series, he created a cohesive body of work that linked his immersion in Bauhaus and Constructivist thought with the mystique of Action Painting, to the degree that Storr credits Smith with being "the first and only member of his circle to systematize the 'all-over' painting," no mean feat in those days.

For all of their formal rigor -- like Mondrian, Smith did not put much faith in the diagonal -- the Louisenberg paintings, as Storr observes, "are intuitively worked out rather than programmed, whimsical rather than studied." One assumes that he is referring to Smith's use of color as well, which, despite the playful mix of warm and cool hues and light and dark tonalities, seems relatively arbitrary. Perhaps I didn't quite get how the colors are "chromatically magnetized," but I'm willing to admit that such a phenomena may exist.

Most enjoyable, however, is how these morphing shapes push at each other, demanding space and attention. That is why the huge late painting is such a disappointment; the way it was executed, with taped edges (viz. see the cover photo of the catalogue, Smith applying a level to one of his clover-like forms), the shapes float free of each other on a blood red ground, inert and static.

Ultimately Smith's modest-sized paintings from this series, possessing a vitality and freshness that was innovative for their time, have over the years inspired and anticipated some of the best painting contemporary American art has to offer.