[Paraview] application specific questions

[Utkarsh Ayachit]

Karina,

> 1.       Will Paraview allow me to specify a differ color bar for the CT
> data ( I’d like to use one of the presets – X-ray) and  the segmented
> objects after the data has been loaded into Paraview? OR do I have to
> specify a “Look UP table” in my VTK files? Currently I am just using the
> “Default” keyword.

ParaView will allow you to pick LUTs for the CT data and the segments
both of which you're reading from the vtk files. ParaView likes to
share lookup tables when the scalar arrays have the same name. If you
run into that situation, you can rename the scalar arrays either in
the VTK files or using  the Calculator filter. (I can give you details
if it comes to that). ParaView does not respect LUTs specified in the
VTK files so "DEfault" is just as good as any other in this case.

>
> 2.       Is there a way to have one file for the CT data and all the
> segmented objects? I will be segmenting a large number of object s from the
> data and loading them into Paraview one at a time would not be efficient. If
> there is such a file, will Paraview allow me to view/un-view each object
> separately?

I am guessing the segmented objects are polygonal (vtkPolyData), in
which case you can easily use the "vtm" format to group the files into
a sequence of blocks in a Multi-Block dataset. This preserves the
information about individual segments as well. YOu can then apply the
"Extract Block" filter to select/un-select the blocks you don't want
to be seen. This functionality is expected to be improved in future so
that you don't have to use the "Extract Block" filter at all.

> 3.        I am currently running Paraview on my desktop (windows 7) which
> has a pretty good processor and 16GB of RAM. I store the CT data as a
> structured point VTK file and the segmented objects as unstructured grid VTK
> files. Some of the CT data sets are pretty large on the order of
> 512x512x1000 points. The volume rendering is not instantaneous when I rotate
> the object. Is this expected ? And if so , is the delay because of the
> processor, the RAM or the graphics card?

What version of ParaView are you using? 3.14 has "smarts" in there to
pick the fastest volume renderer. ParaView should switch to "cheaper"
rendering mode as you interact. Is the delay something that you see
intially and goes away as you keep on moving the mouse or is it
present for each movement of the mouse?

 Also, the rendering for the
> unstructured grid VTK is even slower.  I would think this is expected given
> the delay for the structured grid – I would think Paraview has to work
> harder because of the unstructured nature of the points. Correct? Is there a
> more optimal way to present my data to Paraview?

Yes, unstructured will indeed be much slower. It also leads to lot of
memory bloat so it's generally not  a good idea to convert a
structure-data to unstructured grid unless warranted.

Utkarsh