[Paraview] Time shift not snapping correctly to fractional times

[Eric Monson]

Hello,

I've recently been using the Temporal Shift Scale filter with data  
defined as having time steps every 0.1 units. In this situation, time  
does not always increment or "snap" properly to the data's defined  
time steps. (ParaView 3.3 cvs)

Attached is a toy data set consisting of a single point which travels  
around a radius=10 circle in the XY plane over time -- VTK XML  
Unstructured Grid files along with PVD files describing the time. One  
PVD file has time defined in 0.1 unit steps (dt01), the other is the  
same data defining time in 1.0 unit steps (dt1).  Note: To easily get  
the camera view correct, you might want to add a box source with sides  
= 20, viewed in outline mode.

If the pipeline consists of the original data, defined on 0.1 unit  
time steps, plus a Temporal Shift Scale with Shift = 0.1, and both the  
original and time shifted points are being viewed, then when time is  
incremented (say, though pressing the "up arrow" next to the Time  
display) the points should follow each other around the circle with an  
even spacing. Sometimes both points move forward properly, but  
sometimes the forward one pauses and the other "catches up", and  
sometimes the back one pauses and the forward one gets "ahead".  
Annotate Time also does not always increment properly, either.

If you use the PVD file with 1.0 unit time steps, and a TSS filter  
with shift=1.0, then this doesn't  happen.

Is this to be expected with how the time-snapping works with  
fractional time?

Thanks,
-Eric

P.S. Sorry I used the word "cell" in the data set name: the sim output  
I'm really trying to visualize is of biological cells diffusing in  
space. It's really point data on an unstructured grid.

-----------------------------------------------------
Eric E. Monson
Duke Visualization Technology Group

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