[flotus1]

I have an issue with PV that bothers me every time I want to view or save an animation of particles together with some representation of the underlying flow field.

As long as I only have the particles visible, the animation runs quite fast, lets say in the range of 10ms per timestep.
fast.jpg

The problem is that if I want to show some representation of the flow field in the background like e.g. streamlines, it takes orders of magnitude longer.
awfully_slow.jpg
It seems like the streamlines were recomputed every time step, which is not necessary.
I have a steady-state flow field and only the particle positions change.
I thought that the option "Ignore time" would be what I am searching for, but it has no effect. I ticked "Ignore time" for every object except the particles, but this changes nothing.

My workaround until now was to save an image of the flow representation I need and use it instead of the actual results, but that is not very comfortable.

I have version 4.01 installed right now, but this issue has been bothering me since 3.10.
Any ideas?

[wyldckat]

Greetings Alex,

So, if I understand you correctly, the "LB_results" data remains the same for all time snapshots, is that correct? But whenever you change the file, it seems to reload and recalculate the streamlines.

There are 2 possibilities here:

1. You might have got the "Lock Interactive Render" feature turned on. It's shown here: http://www.paraview.org/Wiki/ParaVie...r_View_General - switch the value to 0, so that it won't hold still for 2 seconds between renders.
2. The data inside "LB_results" might actually change with time, hence the streamlines are always calculated. In this scenario, there are 2 possible fixes:
   1. Select the "Transform" entry after the streamlines and use the menu to choose "File -> Save Data" and save as VTK file the stream lines. Delete the "LB_results" branch and load back the VTK file you had saved.
   2. If it's very slow to calculate the streamlines, then apply the "extract edges" or "extract geometry" or "extract surface" filter (I can't remember which one it's best) save as VTK file.
      Delete the streamlines calculation and load the VTK file. Then apply the filter... er... I think it's the "Resample with Dataset" filter. If you select both the loaded VTK file entry and the "LB_results" entry, you can interpolate the results onto the VTK lines and therefore have the interpolated data on them.
      It's faster in the sense that interpolation alone is quicker, than having to calculate first the streamlines.

Best regards,
Bruno

[flotus1]

Thanks Bruno, your advice helped a lot.

The "Lock Interactive Render" feature was already turned off, so this did not cause the problem.
Both options you supposed in 2. worked for me, although only the "extract surface" filter retained the information of the streamlines.

In order to help me fully understand what I am doing wrong, could you try comment on these issues:
The data inside "LB_results" that contains the flow field actually changes with time. But only because we use a transient solver to obtain a steady-state result. There is only a small amount of time steps and I only want to use the last one.
The particle trajectories were actually calculated based on the last "time step" of the "LB_results" dataset.
So here is the thing: "LB_results" only contains 4 time steps, of which only the last one is needed.
The "Particles.vtk" contains thousands of real time steps showing the actual trajectories of the particles.
So although the time counter in ParaView is constantly higher than the last time step available in "LB_results" during the animation, PV still tries to update the representations based on this dataset?
Then what is the "ignore time" option good for?

[wyldckat]

Hi Alex,

The "ignore time" option only affects the selected source entry in pipeline; it will be certainly frozen in time, although most likely it will be stuck in the first iteration.
But the streamlines are always calculated when a new time snapshot occurs.
Here's how I know this... I've done a few tests with OpenFOAM data in ParaView 3.12.0 and I noticed the following:

1. One entry of a file ".OpenFOAM" is loaded.
2. I apply the "Streamlines" filter to it.
3. It calculates the streamlines on a need basis, namely when the time snapshot is changed.
4. I chose to freeze the time for the ".OpenFOAM" entry.
5. The time controls were restricted and sort-of frozen in time = 0s. But I could still changed from 0 to 1 in steps of 0.1(1), but it did not affect the streamlines filter.
6. I loaded a second entry of the same ".OpenFOAM" file.
7. The time controls were back on and the streamlines were calculated along with the original data. In other words, the second entry broke the time lock on the first entry.

This is probably because ParaView's time controls still have some considerable limitations.

Note: I have not tested with ParaView 4.1.0, to see if the same problem still occurs or not.

Best regards,
Bruno

[flotus1]

Thanks for your effort.