I am a newbie on Arduino, but I am really interested on a prototype designed to measure the section shape of an object using sensors around the piece. I would like to know what sensor is better for small distances and, to avoid the use of lot of sensors I would like to use a system which allows me to move the sensor around the piece to the documentation.
Sorry for my english, if you need more details I can attach a draw if you require it.
What's your budget?
Commercial desktop 3d scanners cost several hundred dollars. Anything you build yourself is probably going to cost a lot more than that.
The best the Arduino can do is take care of the positioning of the sensor and reading it, then transmitting the sensor and position data to a much more powerful device that can actually process it and produce the 3D image.
The sensor will be one of the more expensive parts. It has to be accurate have a very narrow beam. The software that interprets the 3D sensor data will also not come cheap.