[Paraview] [EXTERNAL] Time Synchronization for Case and Geometry Sequences

Thu Dec 1 15:35:51 EST 2016

Huangrui,

I found a work around that I think does what you want. After you load in your two data sets, right click on one of them in the Pipeline Browser and check on the “Ignore Time” option. This will tell ParaView to ignore the time in that data set, so will only visit the time steps in the other data set.

Actually, this _almost_ works. There is in fact a problem (at least with the example data sets you sent us). The imprecision is not uniform. Sometimes the time for field.case is ahead, other times the time for geo_stl.pvd is ahead. So, when you play through the time steps, sometimes the data for which you are ignoring time are skipped because the time is first just before one step and then just after another.

To fix this problem, you can use the Temporal Shift Scale filter to adjust the time of one of the data sets to subtract a bit to ensure that every time hits in between time steps. Here is specifically what I did with the test data that you sent to fix the problem.

1. Load in the field.case and geo_stl.pvd files. Apply both.
2. Add the Temporal Shift Scale filter to geo_stl.pvd. Set the Pre Shift to -0.005. Apply.
3. Right click on TemporalShiftScale1 in the pipeline browser and select “Ignore Time”

Now when you hit play you should get the right amount of time steps with the data you expect loaded.

-Ken

On 12/1/16, 1:58 PM, "Huangrui Mo" <huangrui.mo at uwaterloo.ca> wrote:

    Hello Alan and Ken,

    Thank you very much for your prompt response of my question.

    After testing your suggestions, I found both the Real Time Mode and 
    Sequence Mode can correctly synchronize the
    two data sets with mixed formats, if a correct number of steps is given. 
    However, both of the above two methods
    share a common subproblem: they give artificial time steps that are 
    different with the "true" time moments contained in
    the case (or pvd) files, when a annotated time filter is used, even the 
    specified number of steps matches the true number of case files.

    Regarding the Snap to Timesteps mode and the numerical imprecision of 
    the different times problem raised by Ken, I provided an example
    data set attached in this email. This data set contains the simulated 
    flow field of three airfoils running on a fixed Cartesian background grid.
    Since the Cartesian grid is fixed, therefore, using Ensight format for 
    the field data has the advantage to avoid outputting the grid 
    coordinates in each
    time step but only the physical quantities. To facilitate the testing, I 
    solved this problem exactly twice, the only difference is that one uses 
    Ensight for field data
    and VTK for geometry, the other uses both VTK. Each data sets has 10 
    time sequences, and the time steps in each data sets are all the same.

    When loading the mixed data sets, the field.case + geo_stl.pvd gives 20 
    sequences, and the field.pvd + geo_stl.pvd  gives 10 synchronized sequences.

    Due to the artificial times steps in the Real Time Mode and Sequence 
    Mod, is there a way to synchronize the mixed case in the Snap to 
    Timesteps mode?

    Thanks a lot,
    Huangrui

    On 2016-12-01 01:54 PM, Moreland, Kenneth wrote:
    > Actually, I think Sequence mode is more appropriate than Real Time mode in this case, but I too think that is the answer.
    >
    > To explain more what (we think) is going on: When you load data with time in ParaView, it goes to a Snap to Timesteps mode where it will visit each unique timestep once regardless of how far apart they are. Thus, ParaView is treating the numerical imprecision of the different times as unique time steps. If you switch to Sequence or Real Time mode, ParaView uses its own time units and will provide an even temporal spacing.
    >
    > There is more information about the different animation modes in the ParaView tutorial.
    >
    > -Ken
    >
    > Sent from my iPad so blame autocorrect.
    >
    >> On Dec 1, 2016, at 11:35 AM, Scott, W Alan <wascott at sandia.gov> wrote:
    >>
    >> Not sure if this is the correct answer, but try view/ animation View.  Then, change the Mode to Real Time.  Enter your start time and end time, and number of time steps of interest (i.e., 500).
    >>
    >> Is that what you are looking for?
    >>
    >> alan
    >>
    >> -----Original Message-----
    >> From: ParaView [mailto:paraview-bounces at paraview.org] On Behalf Of Huangrui Mo
    >> Sent: Thursday, December 1, 2016 9:54 AM
    >> To: paraview at paraview.org
    >> Subject: [EXTERNAL] [Paraview] Time Synchronization for Case and Geometry Sequences
    >>
    >> Dear Paraview Developer,
    >>
    >> May you please help me with the following issue:
    >>
    >> Suppose when a solver writes data out, the field data is written in Ensight format, and the time sequence is streamed in "ensight.case".
    >> Meanwhile, the geometry data is written in VTK format, and the time sequence is streamed in "paraview.pvd".
    >> At last, let's assume the number of time sequences is 500.
    >>
    >> Then, when loading into paraview, it does not synchronize the cases in a perfect sense and would show up with 1000 cases. When animating, there is a slight mismatch in time for the field data and geometry data.
    >> However, if I use the VTK format for both the field and geometry data, then paraview does a great job to synchronize the data sets.
    >>
    >> Therefore, my question would be that is it possible to handle time synchronization even for different formats?
    >>
    >> Thank you very much for your time and help, Huangrui
    >>
    >> --
    >> *****************************************************
    >> Huangrui Mo, PhD Candidate
    >> Fluid Mechanics
    >> Department of Mechanical & Mechatronics Engineering University of Waterloo Waterloo, Ontario N2L 3G1, Canada
    >> E-mail: huangrui.mo at uwaterloo.ca
    >> *****************************************************
    >>
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    -- 
    *****************************************************
    Huangrui Mo, PhD Candidate
    Fluid Mechanics
    Department of Mechanical & Mechatronics Engineering
    University of Waterloo
    Waterloo, Ontario N2L 3G1, Canada
    E-mail: huangrui.mo at uwaterloo.ca
    *****************************************************