Probably the simplest way of obtaining 3D data suitable for turning into an object model would be using a Kinect.
For large objects, like buildings, you would need either expensive laser scanners or something which solves the multi-view stereo problem. There are systems capable of doing this, such as Photosynth, but in general it's quite involved with no easy solutions.
For medium range models, such as automotive applications, you could have a pair of cameras aligned in parallel and connected to a PC/laptop then use a utility like v4l2stereo.
For large objects, like buildings, you would need either expensive laser scanners or something which solves the multi-view stereo problem. There are systems capable of doing this, such as Photosynth, but in general it's quite involved with no easy solutions.
For medium range models, such as automotive applications, you could have a pair of cameras aligned in parallel and connected to a PC/laptop then use a utility like v4l2stereo.