| 摘要 |
A drafting device (10) is provided for drawing parallel lines as well as true perspective lines, comprising carriage means (11) movable over a drafting surface (12) on wheel assembly means (20) and (21). A ruler (124) is located on carriage means (11) and has an unobstructed drafting edge (125) constantly co-linear with a true radial line to a chosen vanishing point. Selectively variable ratio transmission means (31), between wheel assembly means (20) and (21), permit ruler (124) to move over drafting surface (12) in a parallel or an arcuate manner about a preset vanishing point on or outside drafting surface (12). Magnet means are included for maintaining wheel assemblies (20) and (21) in frictional contact with drafting surface (12) and brake means are included to lock carriage (11) on drafting surface (12) in selected positions. Presetable stop means are provided to preset a plurality of vanishing points. |
