Samuel P. Geisberg

A Soviet-born mathematician who earned a Ph.D. and taught at Leningrad University before emigrating to the United States in 1974. At Computervision and Applicon, he proposed a radical new approach to CAD based on solid geometry and parametric feature-based modeling. When neither employer would fund the idea, he founded Parametric Technology Corporation in May 1985 with $750,000 in seed capital. Geisberg's defining decision was insisting that attorney Noel Pasternak personally invest $25,000 of the initial $150,000 seed round — a move that ensured Pasternak's full commitment to the venture. Geisberg served as executive vice president of R&D until leaving the company in the late 1990s.

Samuel P. Geisberg was born in St. Petersburg, Russia in 1936 and earned a Ph.D. in mathematics before becoming a professor at Leningrad University. In 1974, he emigrated to the United States with his 11-year-old son, leaving his wife and daughter behind temporarily due to Soviet exit restrictions. He joined Computervision as a software developer, then moved to Applicon where he conceived of parametric, feature-based solid modeling — a CAD paradigm where changing one dimension automatically updates all dependent geometry. When Applicon declined to fund the project, Geisberg founded Parametric Technology Corporation in May 1985. He raised approximately $750,000 in seed funding, built a development team of four to five engineers, and shipped Pro/ENGINEER in 1988. The product's parametric capabilities revolutionized mechanical design, and by 1991 PTC revenue reached $100 million. Geisberg stepped back from day-to-day management when Steven Walske was hired as CEO in December 1986, focusing instead on R&D strategy. He remained on the board and served as executive VP of R&D until the late 1990s, by which time PTC had become a billion-dollar company. Geisberg's mathematical rigor and insistence on a unified data model for all design, analysis, and manufacturing applications established the technical foundation that still underpins PTC's product architecture four decades later.