1. A method, comprising: instantiating, in one or more computer memories, an instance of a three-dimensional scene defined by a collection of document objects, wherein the document objects are encoded in a descriptive language and define respective three-dimensional modeled objects or spaces; controlling contents of the collection of document objects in response to signals received by a processor from one or more client devices; recording, in the one or more computer memories, a sequence of three-dimensional scene states based on respective states of the scene at successive times of a time sequence, including at least position and orientation of three-dimensional objects modeled in the scene; and providing data representing the sequence of three-dimensional scene states to the one or more clients.