[Paraview] Stream Tracer Problem

[Moreland, Kenneth]

Yup, figured it out. There are a couple of problems with the state file you sent me.

First, you have the stream tracer filter connected to the output of the glyph filter. It needs to be connected to the calculator (VectorCalc) filter. I'm sure that was just a silly mistake.

Second, your data set is super extremely long. The dimensions are 45 x 40 x 98,800. As I said in a previous email, if your data is very skinny (or thin), then the point seed for the stream tracer is likely to completely miss the data. The line source doesn't seem to be working either. Perhaps the cells are so long and thin the cell locator or integrator is not operating correctly.

I see you tried to correct this skinniness by using the scale transform in the display properties. This only scaled the data when rendering. The underlying data that filters operate on is still really, really skinny. I advise to never, never, never use the transform options in the display properties. They screw up some other features in ParaView and also lead to pretty confusing behavior even when the result is technically "right" (as you just experienced). I've advocated in the past in getting rid of this feature, but too many people rely on it.

Anyway, the right thing to do is use the transform filter to adjust the scale of the actual data. Once you do that, the data will behave as expected. Attached is a screenshot of some successful streamlines.

-Ken


From: Paul Graham <meteorpaul at gmail.com<mailto:meteorpaul at gmail.com>>
Date: Thursday, November 7, 2013 2:35 PM
To: Kenneth Moreland <kmorel at sandia.gov<mailto:kmorel at sandia.gov>>
Cc: "paraview at paraview.org<mailto:paraview at paraview.org>" <paraview at paraview.org<mailto:paraview at paraview.org>>
Subject: [EXTERNAL] Re: [Paraview] Stream Tracer Problem

Hi Ken,

I have attached a sample of the data to this message along with the saved Paraview state.  Hopefully this will help diagnose why it is not working.

Thanks again for your help.

Paul


On 8 November 2013 02:46, Moreland, Kenneth <kmorel at sandia.gov<mailto:kmorel at sandia.gov>> wrote:
Would it be possible to send a small example of your data to the list so we could try it out? If not, could you at least send a screen shot so we could have a look at the mesh? Right now I'm just making blind guesses.

-Ken


From: Paul Graham <meteorpaul at gmail.com<mailto:meteorpaul at gmail.com>>
Date: Thursday, November 7, 2013 1:26 AM
To: Kenneth Moreland <kmorel at sandia.gov<mailto:kmorel at sandia.gov>>
Cc: "paraview at paraview.org<mailto:paraview at paraview.org>" <paraview at paraview.org<mailto:paraview at paraview.org>>
Subject: [EXTERNAL] Re: [Paraview] Stream Tracer Problem

Hi Ken,

Thanks for your suggestions.  I still haven't worked out why it's not working, but I notice that no data is registering in the Stream Tracer filter.  It's mesh is empty - no points or cells - and the bounding information not available.

I tried a high density Line Source, as you suggested, as well as increasing the number of seed points within the radial ball of the Point Source but without success.  However, both the Line Source and the Point Source correctly display within the domain of the 3D vector field.

The vectors themselves (from the glyph filter) display correctly.

Paul


On 7 November 2013 09:05, Moreland, Kenneth <kmorel at sandia.gov<mailto:kmorel at sandia.gov>> wrote:
That is not a lot of detail to go on so I have to guess what the problem is. It is probably either that the seeds are not intersecting the mesh or that vectors do not yield good lines.

If you mesh is very thin or comprises surface elements, then chances are all the seed points are outside your mesh. The default point source is actually a point cloud with randomly selected points within a sphere of a certain radius. If your mesh is flat, the chance of any seed happening to hit it are extremely low. Try changing to a line source and see if that helps.

It could be that the vectors your creating are not integrating well. It could be that the vectors are pointing off of the mesh (which is also common in thin or flat meshes). Thus it dies before it starts. Or perhaps it has some other feature that makes it difficult to integrate.

-Ken

From: Paul Graham <meteorpaul at gmail.com<mailto:meteorpaul at gmail.com>>
Date: Wednesday, November 6, 2013 2:40 PM
To: "paraview at paraview.org<mailto:paraview at paraview.org>" <paraview at paraview.org<mailto:paraview at paraview.org>>
Subject: [EXTERNAL] [Paraview] Stream Tracer Problem

Hi Everyone,

I am unable to display a Stream Tracer and not sure what is going wrong.  After creating a vector field using the Calculator Filter, I added the Stream Tracer filter using a point source seed (default setting).  The point source  origin is displayed but nothing else.  Can anyone help me as to what I have to do to get the stream lines to show?

Thanks in advance,

Paul

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