Before solving for an optimal truss structure, we must have a clear idea of what purpose we want the structure to serve. For example, a bridge must support some minimum weight along its span, the Eiffel Tower must support observation decks, and roof trusses need to support the roofing material. We model these support requirements as loads, which are placed by the user. Although most structural loads are continuous (e.g. a planar roadbed), appoximating loading as a set of discrete load-points is standard practice within the civil and structural engineering disciplines [Hibbeler 1998].In addition to having external loads, every truss structure must also be supported at one or more points by the ground. For real
structures, the location of these anchors is influenced by topography, geology, and the economics of a particular site, but for our
modeling purposes their positions are specified by the user.
After placement of the anchors and loads, a rich set of free joints
is automatically added and highly connected to all three sets of