Eva is a software designed to help in the early stages of planning architecture and room layout. In an interactive process, based on a given room program or property parameters, different basic approaches are being generated and tested on their verisimilitude. Before going into detail some versions are being excluded or the best ones are being progressed. Compared to other analogue developing processes Eva can record a lot more possible versions in an even shorter time. Eventually this makes it easier for architects or designers to decide on one version and not just see it as an optimizing task. Because of the easily comprehensible graphic illustration of the developing process, it can be shown to the building contractor with the possibility of participation or modification.