Systems and methods are described for animating 3D characters using synthetic motion data generated by motion models in response to a high level description of a desired sequence of motion provided by an animator. In a number of embodiments, the synthetic motion data is streamed to a user device that includes a rendering engine and the user device renders an animation of a 3D character using the streamed synthetic motion data. In several embodiments, an animator can upload a custom model of a 3D character or a custom 3D character is generated by the server system in response to a high level description of a desired 3D character provided by the user and the synthetic motion data generated by the generative model is retargeted to animate the custom 3D character.