Today's commercial CAD systems may add a mechanical simulator to the usual 3D manipulation tools2.5. But the new field of Evolutionary Design (ED)  has the potential to add a third leg to computer-aided design: A creative role. Not only designs can be drawn (as in CAD), or drawn and simulated (as in CAD+simulation), but also designed by the computer following guidelines given by the operator. Thus we envision future Evolutionary CAD systems, ``EvoCADs.''
An EvoCAD system has the human designer in the main role: the designer has an idea or concept for a required object. Some of the requirements can be added to the 3D canvas, creating evolutionary targets that an ED engine uses for evolving a possible design. The output of this evolutionary engine can be modified, tested and re-evolved as many times as desired (figure 2.32).
To demonstrate our conception of EvoCAD, we have built a mini-CAD system to
design 2D Lego structures. This Lego EvoCAD allows the user to manipulate Lego
structures, and test their gravitational resistance using the same structural
simulator we have been using to do ED with Lego bricks. It also interfaces to
an evolutionary algorithm that combines user-defined goals with simulation to
evolve candidate solutions for the design problems. The results of evolution
are sent back to the CAD front-end to allow for further re-design until a satisfactory
solution is obtained.