Plot3D[x y, {x, -2, 2}, {y, -2, 2}]

[Graphics:HTMLFiles/kn5e01s_2.gif]

- SurfaceGraphics -

kyokumen = Plot3D[x y, {x, 0, 1}, {y, 0, 1}]

[Graphics:HTMLFiles/kn5e01s_5.gif]

- SurfaceGraphics -

heimen = ParametricPlot3D[{u, u, t}, {u, 0, 1}, {t, 0, 1}]

[Graphics:HTMLFiles/kn5e01s_8.gif]

- Graphics3D -

Show[kyokumen, heimen]

[Graphics:HTMLFiles/kn5e01s_11.gif]

- Graphics3D -

Show[kyokumen, heimen, ViewPoint-> {2.213, -2.393, 0.91}]

[Graphics:HTMLFiles/kn5e01s_14.gif]

- Graphics3D -