<div>I think that you can just use the cross-product on the vector p1-p2 = V1 and the vector p1-p3 = V2. Then V1 X V2 will give you the direction of the normal. If this normal is in the direction you want than p1,p3,p2 are in anticlockwise order. However if V2 X V1 gives you the normal in the direction you want then p2,p3,p1 is the order you want. You can verify this with a sheet of paper.
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<div>I guess the point is you have to decide what is outside, make sure the normal points in that direction and then the ordering of the points follows the scheme above.</div>
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<div>Hope this helps,</div>
<div> Andrew</div>
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<div><span class="gmail_quote">1/07, <b class="gmail_sendername">PAUL</b> <<a href="mailto:polinzhuo@163.com">polinzhuo@163.com</a>> wrote:</span></div>
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<p><font face="Arial" size="1"><span lang="EN-US" style="FONT-SIZE: 9pt; FONT-FAMILY: Arial">Hello, everyone, </span></font></p>
<p><font face="Arial" size="1"><span lang="EN-US" style="FONT-SIZE: 9pt; FONT-FAMILY: Arial">As we know, we can get the exact direction of a plane, through the order of three arbitrary points on the plane, according to the right –hand rule. But I don't know how to find a way of getting the anticlockwise order of three arbitrary points when I watch an object from outside.(The three arbitrary points are on the object.)
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<p><font face="Arial" size="1"><span lang="EN-US" style="FONT-SIZE: 9pt; FONT-FAMILY: Arial">Paul </span></font></p></div></div><br>_______________________________________________<br>This is the private VTK discussion list.
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<br>-- <br><br>___________________________________________<br>Andrew J. P. Maclean<br>Centre for Autonomous Systems<br>The Rose Street Building J04<br>The University of Sydney 2006 NSW<br>AUSTRALIA<br>Ph: +61 2 9351 3283
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