Worlds are built by adding or subtracting basic 3D volumes. These 3D volumes are called primitives. SED supports many types of fully editable primitives: cones, toruses, staircases, spheres and terrain. There are many parameters for each type of primitive. By modifying these parameters you can create numerous variations of 3D shapes. Vertices on base of cone primitive can be dragged in top view. Top polygon of cone can be stretched and sheared. Vertices of terrain primitive can be extruded using grayscale picture (displacement map) or manually using PgUp/PgDn on vertex under mouse. If triangulation is on (set by combo box near primitive icons on tool bar), vertices can be dragged in all directions.