RE: planar polygon plot
- To: mathgroup at smc.vnet.net
- Subject: [mg16429] RE: planar polygon plot
- From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
- Date: Sat, 13 Mar 1999 02:21:43 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Richard Hsu wrote:
-------------
I want to plot a planar polygon in 3D with shading.
when the polygon is concave, the shading could be wrong.
For a simple example:
Show[ Graphics3D[ Polygon[ { {0,0,0}, {1,0.5,0}, {2,0,0},
{2,2,0}, {1,1.5,0}, {0,2,0} } ] ] ];
I know what Mathematica is doing here, but want to know
if there is a easy way to get correct shading for general
3D planar polygons.
Thanks
------------------------
Is seems you will get want if the first point in the polygon is one of the
points that causes it to be a concave polygon. Specifically either of the
following works for me.
In[1]:=
Show[ Graphics3D[{Polygon[ { {1,1.5,0}, {0,2,0},{0,0,0} ,{1,0.5,0},
{2,0,0},{2,2,0}
} ]
}] ];
(* Graphic not shown *)
In[2]:=
Show[ Graphics3D[{Polygon[ {{1,0.5,0}, {2,0,0},
{2,2,0}, {1,1.5,0}, {0,2,0},{0,0,0} } ]
}] ];
(* Graphic not shown *)
---------------------
I don't understand why you should have to worry about this.
It looks like you need to come up with a clever algorithm that will arrange
the points in an appropriate order for a general polygon. I don't have time
for that right now, but I may post a solution in a week or so.
--------------------
Regards,
Ted Ersek