An interactive computing system comprising: an input for receiving a first series of depth images from a mobile depth camera (102, 400) when in motion and a second series of depth images from the mobile depth camera when static; a real-time camera tracking engine (112, 416) for tracking a position of the mobile depth camera when in motion around an environment; a dense 3D environment modeling system (110, 424) arranged to generate a dense 3D model of the environment from the first series of depth images and position data from the real-time camera tracking engine; and an integration engine (114, 432) arranged to: integrate at least a part of the dense 3D model into an application, wherein to integrate comprises: analysing the dense 3D model to automatically identify objects in the model; where an object is identified, inputting object type and object location information into the application; and adjusting operation of the application based on the input object type and location information, wherein the objects comprise an active object, said active object comprises a display, and adjusting operation of the application comprises adjusting an output of the display; the integration engine (114, 432) further arranged to: track real-time movement in 3D in a region of the environment using the second series of depth images; provide the real-time movement data as an input to the application; and using the knowledge of the relative position of the camera and display, automatically calibrate a pointing device or determine where a user is looking within the environment by additionally using knowledge of the relative position of the user's head and eyes. an input for receiving a first series of depth images from a mobile depth camera (102, 400) when in motion and a second series of depth images from the mobile depth camera when static; a real-time camera tracking engine (112, 416) for tracking a position of the mobile depth camera when in motion around an environment; a dense 3D environment modeling system (110, 424) arranged to generate a dense 3D model of the environment from the first series of depth images and position data from the real-time camera tracking engine; and an integration engine (114, 432) arranged to: integrate at least a part of the dense 3D model into an application, wherein to integrate comprises: analysing the dense 3D model to automatically identify objects in the model; where an object is identified, inputting object type and object location information into the application; and adjusting operation of the application based on the input object type and location information, wherein the objects comprise an active analysing the dense 3D model to automatically identify objects in the model; where an object is identified, inputting object type and object location information into the application; and adjusting operation of the application based on the input object type and location information, wherein the objects comprise an active object, said active object comprises a display, and adjusting operation of the application comprises adjusting an output of the display; the integration engine (114, 432) further arranged to: track real-time movement in 3D in a region of the environment using the second series of depth images; provide the real-time movement data as an input to the application; and using the knowledge of the relative position of the camera and display, automatically calibrate a pointing device or determine where a user is looking within the environment by additionally using knowledge of the relative position of the user's head and eyes. track real-time movement in 3D in a region of the environment using the second series of depth images; provide the real-time movement data as an input to the application; and using the knowledge of the relative position of the camera and display, automatically calibrate a pointing device or determine where a user is looking within the environment by additionally using knowledge of the relative position of the user's head and eyes.