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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi All,</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>My mistake. I hadn’t realized that viewport
coordinates refer to pixel centres. Changing the BL coordinate from (0, 0) to
(0.5, 0.5) did the trick. Does anyone know of any info on coordinate values for
predictable rasterization in VTK?</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>John.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> vtkusers-bounces@vtk.org
[mailto:vtkusers-bounces@vtk.org] <b><span style='font-weight:bold'>On Behalf
Of </span></b>John Platt<br>
<b><span style='font-weight:bold'>Sent:</span></b> </span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>07 April 2005</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> </span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>16:58</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'><br>
<b><span style='font-weight:bold'>To:</span></b> vtkusers@vtk.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [vtkusers] X values of
GetPositionCoordinate() & GetEventPosition()differ by 1 pixel</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>Hi Users,</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>I have a 2-D actor
rendering polydata representing the border of a rectangle as 1 polyline. The
points for the polydata are created using the position of the 2-D actor in
viewport coordinates as follows</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> int *pos1,
*pos2;</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> pos1 =
this->BorderActor->GetPositionCoordinate()-></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
GetComputedViewportValue(this->CurrentRenderer);</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> pos2 =
this->BorderActor->GetPosition2Coordinate()-></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
GetComputedViewportValue(this->CurrentRenderer);</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> vtkPoints*
pts = this->BorderPolyData->GetPoints();</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> int
width = pos2[0] - pos1[0];</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> int height =
pos2[1] - pos1[1];</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
pts->SetPoint( 0, 0,
0, 0 );</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
pts->SetPoint( 1, width, 0, 0 );</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
pts->SetPoint( 2, width, height, 0 );</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>
pts->SetPoint( 3, 0, height, 0 );</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>When trying to select the
left hand edge of the rectangle (0,3), the display value returned from the
interactor using GetEventPosition()[0] is always 1 pixel less than the actors
GetPositionCoordinate()->
GetComputedViewportValue(this->CurrentRenderer)[0].</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>Also, when the border is
drawn using the default actor 2-D position ( (0,0) & (0.5,0.5) ), the left
hand edge is not visible.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>There are no problems
with any of the other 3 edges – picking or displaying.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>Can anybody explain this
behaviour.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>Many thanks.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>John.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'> </span></font></p>
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