[Paraview] Strange behaviour with large datasets

[Moreland, Kenneth]

If your mesh is typical, then probably most of the cells are of good quality, and there are a handful of cells of bad quality.  Thus, when volume rendering most of the cells will be invisible and that handful of cells will have some opacity.

The probable reason that you can see them in a small mesh and not a large one is that the cells are spatially much smaller (with respect to the entire mesh) for the large mesh.  In correct volume rendering, a material of a constant density will have smaller opacity the thinner it gets.  Your cells are probably so small that there is not enough accumulation to actually see them.

You can adjust for the small scale of the cells by adjusting the "Scale" parameter in the Color Scale Editor dialog box.  That parameter is actually a unit length specification for the opacity parameters given.  Setting it to about cell length divided by 10 should give you decent results.  However, an easier and probably more effective approach would be to bag the volume rendering and use the threshold filter to extract the cells of interest (in this case, the bad ones).

-Ken

________________________________
From: paraview-bounces at paraview.org [mailto:paraview-bounces at paraview.org] On Behalf Of Nathanael Inkson
Sent: Tuesday, September 02, 2008 7:31 AM
To: paraview at paraview.org
Subject: [Paraview] Strange behaviour with large datasets

Dear Paraview people,
            I am working with Paraview with very large datasets (around 40Gb). I have written a filter derived from MeshQuality which doesn't seem to display the returned data arrays correctly. I checked with the same mesh and the MeshQuality filter. The same thing happens: I put the output on volume rendering to look at the quality field and the whole dataset is invisible. I have tried rescaling the range but to know avail. Is this a known problem?
Any advice? With smaller meshes the problem disappears and the quality field is visible with volume rendering.

Best Regards

Dr. Nathanael Inkson,

Computational Fluid Dynamics Developer,
Digital Flow Solutions,

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mob:  +  44 7872010167
web:   wirthresearch.com


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