The invention notably relates to a computer-implemented method for designing a 3D assembly of modeled objects. The method comprises rendering on a second computer a 3D assembly of modeled objects by merging a second 3D modeled object with at least one raster image of a first 3D modeled object, the at least one raster image having being streamed from a first computer to the second computer; sending from the second computer to the first computer first data related to the second 3D modeled object for contact computation between the first and second 3D modeled objects; and computing on the first computer a contact between the first and second 3D modeled objects.