Methods of graphic statics were created in the 19th Century, at a time when the pencil and the piece of paper were the common medium. Combined with contemporary graphical capabilities of computers, graphic statics gain new relevance for early-stage structural design. Rather than assuming that modern graphic statics are just a computerized version of classical graphic statics, the old methods leading to the construction of graphic statics diagrams should be reinvented in order for designers to benefit the most from the new digital medium.
Constraint-based graphic statics is a computational framework improving the construction, the control and the capabilities of classical graphic statics substantially. It allows the designer to shape any flow of forces interactively by means of successive purely graphical operations applied either on a diagram representing its form or on another diagram representing its vectorial equilibrium. Taking full advantage of geometry, the techniques enhance the interactive handling of reciprocal diagrams with two features: (1) nodes — considered as the only variables — are constrained within Boolean combinations of graphical regions, and (2) the user modifies the diagrams by means of successive operations whose geometric properties do not at any time jeopardize static equilibrium. This constructive approach enables useful design-oriented capabilities, among which are a direct graphical representation of the entire solution space at hand, and a direct control of the dependencies between design parameters.