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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'>Dear All,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'>I came across this code in vtkPlaneWidget. It is to
calculate the centre of the plane source:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> float center[3];<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[0] = o[0] + (pt1[0]-o[0])/2.0 +
(pt2[0]-o[0])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[1] = o[1] + (pt1[1]-o[1])/2.0 +
(pt2[1]-o[1])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[2] = o[2] + (pt1[2]-o[2])/2.0 +
(pt2[2]-o[2])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'>Isn’t this exactly the same as:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> float center[3];<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[0] = (pt1[0]+ pt2[0])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[1] = (pt1[1]+ pt2[1])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> center[2] = (pt1[2]+ pt2[2])/2.0;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'>but doubles the number of operations???? I may be
missing something (sometimes the most obvious concept is the one that eludes us)
and I always want to learn something that could improve my programming
technique. If I am correct, then is such programming having an adverse effect
on the speed of vtk overall? (It may be that (a) there aren’t many
instances of such coding and (b) these types of calculations are insignificant
in cost versus the core of the rendering etc.).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'>Jim<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><b><font size=3 face=Arial><span lang=EN-IE
style='font-size:12.0pt;font-family:Arial;font-weight:bold'>Jim Robinson<o:p></o:p></span></font></b></p>
<p class=MsoNormal><font size=3 face=Wingdings><span lang=EN-IE
style='font-size:12.0pt;font-family:Wingdings'>+</span></font><span lang=EN-IE> </span><font
size=2 face=Arial><span lang=EN-IE style='font-size:10.0pt;font-family:Arial'>42
Rivergrove,</span></font><span lang=EN-IE><o:p></o:p></span></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> Glanmire,</span></font><span
lang=EN-IE><o:p></o:p></span></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> Co. <st1:City
w:st="on"><st1:place w:st="on">Cork</st1:place></st1:City>,</span></font><span
lang=EN-IE><o:p></o:p></span></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-IE style='font-size:
10.0pt;font-family:Arial'> <st1:place
w:st="on">Eire</st1:place></span></font><span lang=EN-IE><o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face="Wingdings 2"><span lang=EN-IE
style='font-size:12.0pt;font-family:"Wingdings 2"'>'</span></font><span
lang=EN-IE> +353 21 4822028<o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-IE
style='font-size:12.0pt'> +353
87 2393010<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face=Wingdings><span lang=EN-IE
style='font-size:12.0pt;font-family:Wingdings'>-</span></font><span lang=EN-IE> <font
color=blue><span style='color:blue'><a href="mailto:jrobinson@eircom.net">jrobinson@eircom.net</a></span></font><o:p></o:p></span></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-IE
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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