Ensaio 04 is a geometric study of a curved surface built through straight planes of plywood, resulting in a perspective deformation. The exercice proposed presents a scenic element related to the theater, which is also an exercise of scale since it relates the building with the public space, creating a temporary urban scenary. Ensaio 04 is a strange object due to the illusion that it creates to the human eye, and because of the relations of shadow/light, full/empty that change during the day.