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<DIV><FONT face=Arial size=2>Hi all,</FONT></DIV>
<DIV><FONT face=Arial size=2>I have problem using vtkVolumeTextureMapper3D
class. Originally I developed </FONT><FONT face=Arial size=2>my volume rendering
using VTK 4.2 with Visual Studio 2003. In this, I was </FONT><FONT face=Arial
size=2>using vtkVolumeRayCastMapper. This was later migrated to VTK 5.0 and
Visual </FONT><FONT face=Arial size=2>Studio 2005. I wanted to try, other
mappers available in VTK 5.0. My code </FONT><FONT face=Arial size=2>and update
strategy for original mapper migrated without any hitch. It seems </FONT><FONT
face=Arial size=2>to be working with vtkFixedPointVolumeRayCastMapper (I am less
interested in </FONT><FONT face=Arial size=2>using it). First let me outline how
I setup my rendering and update it (as </FONT><FONT face=Arial size=2>in
original development that works for ray cast mappers).<BR>1. Create a
vtkStructuredPoints object of proper settings (origin,dimension, </FONT><FONT
face=Arial size=2>spacing and scalar type of unsigned short).<BR>2. Fill all
scalars with ZERO values (this is for my requirement)<BR>3. Create volume with
appropriate volume property, color/opacity transfer </FONT><FONT face=Arial
size=2>functions et cetera.<BR>4. Add it to renderer, renderer to
renderwindow.<BR>5. I also have an outline added to renderwindow but I think
that does not </FONT><FONT face=Arial size=2>matter for the problem at
hand.<BR>6. RenderWindow becomes visible.<BR>7. Data aquisation and data
processing begins.<BR>7. Result of data processing is used to update the
structured points and </FONT><FONT face=Arial size=2>updated volume is rendered.
(Updates may happen several times).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Problem I have in using vtkVolumeTextureMapper3D is
that the render window </FONT><FONT face=Arial size=2>remains blank even after
all data aquisation and processing is over. </FONT><FONT face=Arial
size=2>Interacting with render window (in case render has not occurred) also
does </FONT><FONT face=Arial size=2>not change the render window's
appearance.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>In Step 2 above, if I fill the scalars array with
some high value then the </FONT><FONT face=Arial size=2>render window shows
rendered volume. As my data updating logic does not </FONT><FONT face=Arial
size=2>update all voxels when processing ends I cannot use this approach as it
</FONT><FONT face=Arial size=2>leaves regions of volume with wrong
color.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>This viewing related code is in separate
class/control that I can use </FONT><FONT face=Arial size=2>without the data
aquisation/processing part. I can read vtkStructuredPoints </FONT><FONT
face=Arial size=2>data from disk file and view it. When I do this the volume
displays as </FONT><FONT face=Arial size=2>expected (resampling done internally
is understandable).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I am wondering if this is happening when all
scalars are ZEROs, because </FONT><FONT face=Arial size=2>somewhere the mapper
(or some related object) is encountering (possibly) </FONT><FONT face=Arial
size=2>divide by ZERO, going into an invalid state and not regaining valid
state.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Is my doubt about divide by ZERO error correct? If
so what I can do to avoid </FONT><FONT face=Arial size=2>this problem? Delayed
initialization is one thing that comes to my mind but </FONT><FONT face=Arial
size=2>that makes the code complex. Can anyone suggest me a way out of this
</FONT><FONT face=Arial size=2>situation?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Looking forward to any comments / suggestion from
you. Let me know if some additional information is needed before this question
can be addressed and I will provide that information.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks and regards</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Vidyadhar</FONT></DIV></FONT></DIV></BODY></HTML>