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<p class=MsoNormal><span lang=EN-US>Hi all,<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 want to convert an estimated camera pose
(for an augmented reality application) given as vtkMatrix4x4 to a vtkCamera`s
position, focal-point and view-up vector. Position is trivial, but I have some
doubts concerning the current calculation of the focal point and the viewUp
vector which is as follows:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>// camPose: vtkMatrix4x4*</span><span
lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>double
viewPlaneNormal[3];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>double
focalPoint[3];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>double
viewUp[3];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> viewPlaneNormal[0]
= camPose->GetElement (2,0);<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>
viewPlaneNormal[1] = camPose->GetElement (2,1);<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>
viewPlaneNormal[2] = camPose->GetElement (2,2); <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> // focal point<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> focalPoint[0]
= position[0] - viewPlaneNormal[0];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> focalPoint[1]
= position[1] - viewPlaneNormal[1];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> focalPoint[2]
= position[2] - viewPlaneNormal[2];<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> // ViewUp<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> viewUp[0] = camPose->GetElement
(1,0);<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> viewUp[1] = camPose->GetElement
(1,1);<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> viewUp[2] = camPose->GetElement
(1,2);<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 problem is that the camera is slightly
at the wrong position when using these calculated parameters. If I manually
adjust the camera afterwards with<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>m_Renderer->GetActiveCamera()->Elevation(2.5);<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>m_Renderer->GetActiveCamera()->Azimuth(0.5);<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 result is the one I want (the real
camera and the virtual camera are pretty good aligned). <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Actually, the estimated camPose has a small
reprojection error, that`s why I suspect I have a mistake in setting up the
camera.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>The other thing which crossed my mind is
the calculation of the view angle which is implemented like this:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US> double
viewAngle = 2 * atan( ( height / 2 ) / m_FocalPoint[1] ) * 180 / vnl_math::pi;<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>
m_Renderer->GetActiveCamera()->SetViewAngle(viewAngle);<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>So the question is if you see any obvious
mistakes in these calculations or if you have any ideas why the camera is
slightly misaligned.<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>Thanks in advance,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Michael<o:p></o:p></span></p>
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