Rets was born in Paris with Belgian parents and moved to Liège in 1914, where he started studying at the academy in 1920. In 1945 he became a member of the APIAW (association for the intellectual and artistic progress in Wallonia). The following year he exhibited at the Jeune Peinture Belge. His early work was influenced by cubism and later evolved to geometric abstraction, mainly inspired by the works of Magnelli. With his thoughtful approach Rets found that a constructive and expressive manner best fit with his temperament. This approach is related to Delahaut’s approach, with whom he became friends. He was a member of various groups such as Art Abstrait (end of 1953), Formes (1956) and Art Construit (1960). In 1954 he signed the manifest of Spatialisme. 

Rets was focused on the proportions between colours and shapes. From 1956 onward he worked in relief. This new approach resulted in art integration projects. In the 1960’s he introduced neons in his works and made art that is related to the optical arts. Until the end of his career in 1990, he stayed faithful to his artistic assumptions.