[Paraview] application specific questions

[Utkarsh Ayachit]

Karina,

> ...And then you are saying I should be able to use the "LUT Editor" in Paraview individually for each of my files(*.vtk) after loading them in manually, right?

Yes. Also, is the scalar for each segment constant for that segment?
In that case you may want to name the scalar using the same name for
all the segments but give each one a different scalar value. Then when
you load it, you can color all segments using the same scalar array
but specify a LUT that spans the range for scalar values provided by
all segments.


> Can I use *.vtm to group a bunch of "unstructured grid" blocks of data? If yes, is there some advantage of using "Polydata" instead of "unstructured grid" for the segments?

Unstructured is just fine. vtm can support blocks comprising of
unstructured datasets. Note that vtm requires  the blocks to be
specified using the VTK-XML formats (and not legacy VTK) so you'll
have to write *.vtu files for your segments.

> So if load my *.vtm file into Paraview, is there a quick way to select a different LUTs for each segment? OR will I have to manually extract each block and select a LUT? I can see how this might get cumbersome as the number of segments increase.

Alas, that's what you have to --- extract each one to color it. But if
we're talking of a constant scalar for the entire segment, things
might get easier by the solution I suggested earlier.

> I was actually hoping I could somehow specify the LUT in the vtk file. But you said earlier this is not recognized in Paraview, right? Any thoughts?

Yup, ParaView won't respect LUTs in the vtk file. But you can specify
the color scalar (RGB) in the data directly. SImply create a scalar
array that's of the type unsigned-char with 3 components and the color
using that array. ParaView will still try to create a LUT by default,
but on the display tab, you should then be able to uncheck "Map
Scalars" and the colors specified in the data will be used directly. I
am not sure I've expressed it clearly here, so let me if it isn't
obvious.

> I am using v3.14.0. For the unstructured grid data , the volume rendering displays almost like a surface rendering while I am moving the mouse. And then there is a delay one I have settled on a position ( not pressing the  left-button on the mouse") and then I see the volume rendering.

Ah! You're using unstructured grid volume rendering. Yes, that'd do
what you say. And here the delay is due to CPU. We only have CPU
volume renderers, if I am not mistaken. Again, if your data is a
structure data, I'd leave it as ImageData. It should perform much
better.

Utkarsh