1. A method comprising: displaying a synthetic 3D scene; identifying at least one gesture or posture carried out by at least one body part of the user; deriving a vector that spatially represents the identified gesture or posture; transforming the vector into a continuous movement or action in the synthetic 3D scene, based on at least one of an angle of the vector and a length of the vector, wherein a speed of the movement is based on a value of the angle; and modifying the synthetic 3D scene to reflect the movement or action in the synthetic 3D scene.