A system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment...http://www.google.com.au/patents/US5785918?utm_source=gb-gplus-sharePatent US5785918 - Method and apparatus for production of three-dimensional objects by stereolithography 
