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<p class="MsoNormal"><span style="color:#1F497D">I tried to post on vtkusers but had no success yet, so I am trying on vtk-developers.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Remy<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> vtkusers-bounces@vtk.org [mailto:vtkusers-bounces@vtk.org]
<b>On Behalf Of </b>Rémy Trichet<br>
<b>Sent:</b> Wednesday, February 13, 2013 11:44 AM<br>
<b>To:</b> vtkusers@vtk.org<br>
<b>Subject:</b> [vtkusers] Loss of precision vtkCutter with vtkPlanes with vtk 5.10.1<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am trying to use a vtkCutter with vtkPlanes as CutFunction, and then get the output.<o:p></o:p></p>
<p class="MsoNormal">I set a vtkPlane with a normal (0.0, 0.0, 1.0) and an origin of (-1.0, -1.0, 0.5).<o:p></o:p></p>
<p class="MsoNormal">My source is half a sphere centered on (-1.0,-1.0,0.5) and with z > 0.5.<o:p></o:p></p>
<p class="MsoNormal">When I do the cut, and try to get the output, this is empty.
<o:p></o:p></p>
<p class="MsoNormal">I try to cut the entire sphere instead of only a half with the same vtkPlane and get the output (with vtkPolyData::GetPoint(i)) and<o:p></o:p></p>
<p class="MsoNormal">I see that the resulting points have a z = 0.49999999046325684 instead of 0.5, which explains that the output is empty when I use half the sphere.
<o:p></o:p></p>
<p class="MsoNormal">I am only using doubles and the vtk methods I am calling return also doubles, so I am wondering why this happens, and if I am doing something wrong?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here is the sample :<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkPlane</span>>
<span style="color:#010001">plane3</span> = <span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkPlane</span>>::<span style="color:#010001">New</span>();<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">plane3</span>-><span style="color:#010001">SetNormal</span>(0.0,0.0,1.0);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">plane3</span>-><span style="color:#010001">SetOrigin</span>(-1.0,-1.0, 0.5);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkSTLReader</span>>
<span style="color:#010001">roiModelReader</span> = <o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkSTLReader</span>>::<span style="color:#010001">New</span>();<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">roiModelReader</span>-><span style="color:#010001">SetFileName</span>(<span style="color:#A31515">"HalfSphere.stl"</span>);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">
roiModelReader</span>-><span style="color:#010001">Update</span>();<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkCutter</span>>
<span style="color:#010001">cutterForROI</span> =<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">vtkSmartPointer</span><<span style="color:#010001">vtkCutter</span>>::<span style="color:#010001">New</span>();<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">cutterForROI</span>-><span style="color:#010001">SetInputConnection</span>(<span style="color:#010001">roiModelReader</span>-><span style="color:#010001">GetOutputPort</span>());<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">cutterForROI</span>-><span style="color:#010001">SetCutFunction</span>(<span style="color:#010001">plane3</span>);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">cutterForROI</span>-><span style="color:#010001">Update</span>();</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:#010001">vtkPointSet</span>* <span style="color:#010001">dataSet</span> =
<span style="color:#010001">cutterForROI</span>-><span style="color:#010001">GetOutput</span>();<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:blue">
int</span> <span style="color:#010001">nbrPoints</span> = <span style="color:#010001">
dataSet</span>-><span style="color:#010001">GetNumberOfPoints</span>(); // = 0 with half the sphere<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New"">
<span style="color:blue">double</span>* <span style="color:#010001">point</span>;
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:blue"> for</span><span style="font-size:10.0pt;font-family:"Courier New"">(<span style="color:blue">int</span>
<span style="color:#010001">i</span> = 0; <span style="color:#010001">i</span><<span style="color:#010001">nbrPoints</span>; ++<span style="color:#010001">i</span>)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New""> <span style="color:#010001">point</span> =
<span style="color:#010001">dataSet</span>-><span style="color:#010001">GetPoint</span>(<span style="color:#010001">i</span>); // point[2] = 0.</span> 0.49999999046325684 when using the whole sphere<span style="font-size:10.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Remy Trichet<o:p></o:p></p>
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