Camera space synthesis of motion effects emphasizing a moving object in 4D films

Four-dimensional (4D) films, which provide special physical effects to the audience with audiovisual stimuli, are gaining more popularity and acceptance. One of the most frequent 4D effects is the object-based motion effect, which refers to the vestibular stimulus generated by a motion chair to emphasize a moving object of interest, e.g., the flying iron man, displayed on the screen. In this paper, we present an algorithm for synthesizing convincing object-based motion effects automatically from a given object motion trajectory. While previous approaches use the 2D object position on the screen as input, our method takes the 3D position and orientation of the object in the camera space and computes its motion proxy that reflects both the object translation and rotation, as well as its size to the viewers' eyes. The proxy is determined based on the results of a perceptual experiment that presents an optimal additive rule of the translation and rotation information scaled by the object's visual size. The motion proxy is fed to a motion cueing algorithm (MCA) that computes the command using a washout filter or model predictive control. The most appropriate MCA for our purpose is selected from six candidates by a user study. We also consider the effects of visual perception by incorporating two types of motion field equations into the computation of the visually perceived velocity. The results of a user study indicate that our algorithm can generate compelling object-based motion effects that better enhance the 4D film viewing experience than the previous methods.