The German car designer Claus Luthe, who has died aged 75, was one of the most important figures in postwar European car styling, overseeing a generation of handsome 1980s and 90s BMW body designs that took the Bavarian firm to new heights of profitability. But his breakthrough car was the NSU Ro80 (Ro for rotary, 80 its design number), a beautiful, futuristic wedge from 1967 anticipating today's clean, aerodynamic saloons. Its influence is acknowledged in the current generation of Audis.
It is only relatively recently that Luthe's authorship of the Ro80 has become widely known. In 1967, NSU wanted to retain the anonymity of its design team, so when some English journalists suggested that the Ro80 had been designed in Italy, neither NSU nor Luthe did anything to quash the rumour.
Luthe was the second of five children. Born into a deeply religious Catholic family in Wuppertal, North Rhine-Westphalia, he was the son of a cabinetmaker who died on the eastern front in 1945. Claus wanted to follow his older brother and become an architect, but instead completed an apprenticeship (1948-54) at the coachbuilding firm of Voll in Wurzburg, working on bus designs. He joined the styling department of Fiat's German outpost Deutsche Fiat AG at Heilbronn in 1954 - styling a local version of the Fiat 500 - but soon moved to NSU at Neckarsulm.
After a near 30-year gap, this famous moped and motorcycle producer was about to resume car manufacture. Its 1958 Prinz model was a strong rival to the VW Beetle, and Luthe was given the task of styling the second generation of these cars, launched in 1961.
With a bigger, wealthier West German middle class emerging, NSU had ambitions to produce a larger car - with larger profit margins - to take on Mercedes and BMW. The firm had already pioneered Wankel rotary engines in a limited production sports car - the Wankel Spider - and gained much technological credibility.
In 1961 Luthe was handed the task of creating a mid-range, front-wheel drive saloon around this technology. He was given a free hand, a rare privilege in car design even then, to come up with a futuristic shape that reflected the radical engineering and compact dimensions of the two-rotor 115bhp engine.
By 1963 the basic shape was established. His sketches and clay models show that Luthe knew what he wanted from the beginning - an elegant rising wedge with a slim nose and lots of glass.
The Ro80 astonished Frankfurt Motor Show visitors when it made its debut in 1967, but its acceptance was far from universal. Luthe, mingling with the Frankfurt crowds, remembered hearing mostly negative comments about the new car.
But connoisseurs recognised the fast, refined Ro80 as a masterpiece, a car that made everything around it appear dated. Much was made of the car's aerodynamics in 1967. It was a low, drag shape, one of the lowest of its time, but Luthe's profile for the vehicle was instinctively aerodynamic. It was not put into a wind tunnel until the design was nearing completion.
Almost 40,000 NSU Ro80s were made in 10 years of production, and Luthe hardly raised a pencil to the design. But problems with the advanced rotary engine destroyed NSU's fragile finances and the firm was absorbed by the VW/Audi group in 1969.
Luthe stayed with VW for seven years, producing the VW K70 (conceived by NSU as a cheaper, piston-engined alternative to the Ro80), the first VW Polo and the Audi 100.
When he became BMW's chief designer in Munich in 1976, the company had a reputation for producing boxy, conservative-looking cars. In his 14 years with the firm, he maintained the brand's aura of visual restraint while making each successive model sleeker and more elegant. He rejected any design that could be seen as offering "optical environmental pollution" and created two generations of 3 and 5-series cars, the 1985 and 1994 7-series luxury saloons and the 850 coupe. He is also credited with the K100 motorcycle.
Luthe's career at BMW ended abruptly on Good Friday 1990. He stabbed and killed his 33-year-old son Ulrich in the midst of an argument. He was convicted of the murder but did not have to serve his 33-month jail sentence. Though BMW offered him his job back, he soon opted for early retirement while remaining a design consultant.
Colleagues at BMW knew nothing of Luthe's troubled life with his eldest offspring. Ulrich was the first of Claus and Gertrude Luthe's four children, born in 1956, three years after they married. Because of Gertrude's multiple sclerosis, undiagnosed until 1971, Luthe often assumed the roles of both parents and was particularly close to Ulrich, who suffered from a stutter. However, by his early teenage years, Ulrich was becoming troublesome. He did not complete his education and in the 1970s and 80s became increasingly addicted to alcohol and pills. At the time of the tragedy, Ulrich was particularly unstable, his girlfriend having died from an overdose.
Increasingly immobile in his later years, Luthe was an enthusiastic honorary member of several NSU Ro80 clubs.
He is survived by Gertrude, twin sons Christopher and Robert, and daughter Barbara.
· Claus Luthe, car designer, born December 8 1932; died March 17 2008