This lecture by EPFL associate Professors Bernard Cache and Nicola Braghieri delves into the challenges architects face with interoperability and the development of design tools. From the history of projective geometry to the current use of Open Source tools, the lecture explores the need for dynamic interoperability tools and native IFC design tools. It also discusses the importance of supporting Open Source development in the architectural community, highlighting the role of public actors and private initiatives. The presentation showcases practical examples and solutions, such as Speckle for interoperability and Rhino.Inside for design integration, emphasizing the shift towards open-source solutions in architecture.