A real-time video targeting (RVT) system may leverage network-based computation resources and services, available 2D or 3D model data, and available viewer information to dynamically personalize content of, or add personalized content to, video for particular viewers or viewer groups. When playing back pre-recorded video to viewers, at least some objects or other content in at least some of the scenes of the video may be replaced with objects or content targeted at particular viewers or groups according to profiles or preferences of the viewers or groups. Since the video is being rendered and streamed to different viewers or groups in real-time by the network-based computation resources and services, any given scene of a video may be modified and viewed in many different ways by different viewers or groups based on the particular viewers' or groups' profiles.