Dynamic virtual content(s) to be superimposed to a representation of a real 3D scene complies with a scenario defined before runtime and involving real-world constraints (23). Real-world information (22) is captured in the real 3D scene and the scenario is executed at runtime (14) in presence of the real-world constraints. When the real-world constraints are not identified (12) from the real-world information, a transformation of the representation of the real 3D scene to a virtually adapted 3D scene is carried out (13) before executing the scenario, so that the virtually adapted 3D scene fulfills those constraints, and the scenario is executed in the virtually adapted 3D scene replacing the real 3D scene instead of the real 3D scene. Application to mixed reality.