Computer aided construction of stone walls. Rocks are scanned and a wall is built in the virtual world by software fitting irregular polyhedra into a regular structure. When suitable rocks are found, the computer outputs instructions as to the position and orientation of each rock. Rocks weighing up to many tonnes could be scanned using a 3D laser scanner and stored at the quarry while computers at nearby building sites access the data and order individual rocks to be placed in sea walls, retaining walls, river levees, etc. Locally sourced rock rubble requires very little energy to produce (it is a building material with very low embodied energy) so its use as a building material results in very low levels of greenhouse gas emissions. It's a work in progress by Malcolm Lambert and Intresto Pty Ltd in Sydney, Australia; see www.intresto.com.au (the name, Intresto, comes from the "intelligent rearrangement of stone")