Re: making a plane

*To*: mathgroup at smc.vnet.net*Subject*: [mg24228] Re: making a plane*From*: adam_smith at my-deja.com*Date*: Sat, 1 Jul 2000 03:22:00 -0400 (EDT)*References*: <8jhcqf$q1i@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

You need to use "Polygon" in the Graphics3D routine. See the following code snippet. I defined your 4 points with names "data#" data1 = {0.0517, 0.0847, 0.1004} data2 = {0.0517 , -0.0187 , 0.0344} data3 = {-0.0517 , 0.0187 , 0.0690} data4 = {-0.0517 , -0.0847 , 0.0030} Show[Graphics3D[ {Polygon[{data1, data2, data3}], Polygon[{data2, data3, data4}]}]] This turns out looking fine. I am always cautious about using a graph to judge if two things are coplanar - They might be close enough to look like it, but in reality are slightly "off". You should confirm that they are indeed coplanar by checking the cross products of the vectors to see if they yield the same normal vector defining the plane. Here is my (inelegant) way: line12 = line12/Sqrt[(line12.line12)] line13 = line13/Sqrt[(line13.line13)] line34 = line34/Sqrt[(line34.line34)] line24 = line24/Sqrt[(line24.line24)] In[46]:= Cross[line12, line24] Out[46]= {0.0714131, -0.439356, 0.688325} In[47]:= Cross[line13, line34] Out[47]= {0.0714131, -0.439356, 0.688325} As we see the two cross products yield the same results - confirming the the 4 points do indeed lie in the same plane. In article <8jhcqf$q1i at smc.vnet.net>, "KHS" <khs at procd.sogang.ac.kr> wrote: > For given 4 points like this, > > 0.0517 , 0.0847 , 0.1004 > 0.0517 , -0.0187 , 0.0344 > -0.0517 , 0.0187 , 0.0690 > -0.0517 , -0.0847 , 0.0030 > > I thought these points should be on the one plane.... > so I make > > c=Show[Graphics3D[ > > [{{ > 0.0517 , 0.0847 , 0.1004},{ 0.0517 , -0.0187 , 0.0344},{ > -0.0517 , 0.0187 , 0.0690},{ -0.0517 , - 0.0847 , > 0.0030}}]],Axes->Automatic, > PlotRange->{{-0.15,0.15},{-0.15,0.15},{-0.15,0.15}}]; > > But, the figure is so strange....It looks like 2 planes...I don't why..Please help me! > > Thanks in advance! > > Sent via Deja.com http://www.deja.com/ Before you buy.