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<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Last few days I’ve been struggling to find the cause of a strange contouring effect caused, I think, by vtkMapper::MapScalarsToTexture()<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // Get the texture map from the lookup table.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // Create a dummy ramp of scalars.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // In the future, we could extend vtkScalarsToColors.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> double k = (range[1]-range[0]) / (ColorTextureMapSize-1);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> vtkFloatArray* tmp = vtkFloatArray::New();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> tmp->SetNumberOfTuples(ColorTextureMapSize);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> float* ptr = tmp->GetPointer(0);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> for (int i = 0; i < ColorTextureMapSize; ++i)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> *ptr = range[0] + i * k;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> ++ptr;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I set the color scale to have 3 colors, and, as you can see, when using color interpolation before mapping, I get 2 almost identical greens, neither of which matches the green of the color scale. This happens only when
I run our application under Windows remote desktop. When I run a local installation on Windows, or a VNC session on Linux, the colors are fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I accidentally came across issue 7887 while studying vtkContourValues::GenerateValues()
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> for (i= 0; i < numContours; ++i)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // no we cannot factorize the ratio<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // (range[1] - range[0])/(numContours - 1) out of the loop.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // we want the whole expression to be evaluated on the FPU.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> // see bug discussion: http://www.vtk.org/Bug/view.php?id=7887<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> this->SetValue(i, range[0] + i*(range[1] - range[0])/(numContours - 1));<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The same loop occurs in said method of vtkMapper but here the multiplier is calculated outside the loop. I suspect that this may cause the difference in behavior. I have no way for testing it though. Could someone please
try to reproduce? Should I file this as an issue in mantis?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks a lot,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial","sans-serif";color:black;mso-fareast-language:NL">Andreas Buykx<o:p></o:p></span></b></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial","sans-serif";color:black;mso-fareast-language:NL">Senior Software Engineer<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial","sans-serif";color:black;mso-fareast-language:NL"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span lang="EN-US" style="font-size:11.5pt;font-family:"Arial","sans-serif";color:#CB2027;mso-fareast-language:NL">TNO DIANA BV
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<p class="MsoNormal" style="text-autospace:none"><i><span lang="EN-US" style="font-size:8.0pt;font-family:"Arial","sans-serif";color:black;mso-fareast-language:NL">Software Developers and Analysis Consultants for Civil and Geotechnical Engineering
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<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black;mso-fareast-language:NL">Delftechpark 19a, 2628 XJ, Delft, The Netherlands
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<p class="MsoNormal" style="text-autospace:none"><b><i><span lang="EN-US" style="font-size:9.0pt;mso-fareast-language:NL"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span lang="EN-US" style="font-size:9.0pt;mso-fareast-language:NL">…be green keep it on screen</span></i></b><span lang="EN-US" style="mso-fareast-language:NL"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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