The multiple means of making art after the end of illusionism led these artists to create performances, sculptures, earthworks, tableaux, furniture, shaped canvases, and more, using unusual materials. They explore the process of making forms and giving meanings to those forms. In this idea art, their focus is as often social and psychological as artistic. Some of their activities enlist engineering and construction techniques, others compose texts or scripts that are central to their art. Some cast the viewer in the role of a spectator, while the others demand active participation. The sources for their concepts and art works are equally diverse; the delicate proportions and balance of Early Renaissance painting, the exploration of the surface of the moon, the structure and inventions of vernacular architects, to name only a few.