1. An image processing apparatus comprising: a three-dimensional model storage unit configured to store a three-dimensional model data expressing a three-dimensional model of a three-dimensional region, positions of a plurality of devices including a camera disposed in the three-dimensional region as positions in the three-dimensional model, and a plurality of device icons expressing types of the devices in the three-dimensional model; an acquiring unit configured to acquire a shot image taken at the camera and a shooting direction when shooting; a composing unit configured to determine a view point with respect to the three-dimensional model according to the camera position disposed in the three-dimension region, generate a three-dimensional model by disposing the device icons corresponding to the device types on positions of the devices stored in the three-dimensional model storing unit according to the determined view point and the shooting direction, generate a two-dimensional projection image that the three-dimensional model is projected onto a two-dimensional plane, and generate a composite image by composing the shot image in a predetermined region on the generated two-dimensional projection image; and an output unit configured to output the composite image.