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<p class=MsoNormal>Folks,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>We're setting the UserMatrix of an actor to... surprise,
surprise... transform the actor. Nothing exciting, right? <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Wrong, because the last row of our matrix is not the trivial
[0 0 0 1]. This is handled well enough in OpenGL, but the bounds calculation
(in vtkActor::GetBounds()) is seriously wrong because it is doing a linear
transformation of the bbox it gets from the mapper (Transform is a
vtkLinearTransform):<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"'> fptr = bbox;<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'>for</span>
(n = 0; n < 8; n++) <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:blue'>this</span>->Transform->TransformPoint(fptr,fptr);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> fptr += 3;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>
}</span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The easiest fix I found for the issue was the following
(force call to InternalTransformPoint of vtkHomogeneousTransform):<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"'> fptr = bbox;<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'>this</span>->Transform->Update();<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'>for</span>
(n = 0; n < 8; n++) <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:blue'>this</span>->Transform->vtkHomogeneousTransform::InternalTransformPoint(fptr,fptr);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> fptr += 3;<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>The change doesn't cause any tests to fail (for me)... and
it seems like a reasonable change (perhaps should be made in vtkImageActor and
vtkVolume as well?)... but I wanted to put it out there (before I committed and
pushed the change), because it is seriously likely that I'm not considering
some other special "situations", or perhaps the "right" way
to fix this, or ????<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Rusty<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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