Object creation requires placement of the object in the scene.
Though this figure suggests a perspective camera, we use a parallel projection in our application. The first rule determines object placement except for translation along the view direction. A tabletop is created and initially rests on the floor. To insert a leg under the tabletop, the vertical stroke of the leg is dran to form a T junction with the table's edge. The tabletop is automatically raised off the floor, and the leg touches both the floor and the underside of the table.