AutoCAD cannot display a proxy entity using the object's worldDraw() or viewportDraw() functions because the parent application is absent. It uses information in the entity's graphics metafile, which contains data derived from the entity's worldDraw() or saveAs() function when the drawing was last saved (with the SAVE or SAVEAS command). The display format is either that of the entity itself, or a bounding box indicating the volume inhabited by the entity. The format is determined by the setting of the PROXYGRAPHICS system variable at the time the drawing is saved. The bounding box format is useful primarily to minimize the size of the output file when the data for custom entities is large.