Systems, methods, devices, and other techniques for rendering content in a 3D environment. In some implementations the system includes a memory subsystem, a communications interface, a rendering engine, an input handling apparatus, and a virtual object manager. The memory subsystem is configured to store first data that (i) defines a three-dimensional (3D) environment and (ii) identifies a virtual object in the 3D environment. The communications interface is configured to transmit requests over a network for third-party content to display with the virtual object in the 3D environment and to receive third-party content responsive to the requests. The rendering engine is configured to use the first data from the memory subsystem to render the 3D environment for presentation on a display device, including rendering the virtual object at a specified location of the 3D environment in a first mode in which the virtual object displays a first set of third-party content.