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IDProjectCategoryView StatusDate SubmittedLast Update
0015441ParaView(No Category)public2015-04-29 16:552016-08-12 09:59
ReporterAlan Scott 
Assigned ToCory Quammen 
PrioritynormalSeverityminorReproducibilityhave not tried
StatusclosedResolutionmoved 
PlatformOSOS Version
Product Versiongit-master 
Target Version5.1Fixed in Version 
Summary0015441: Below range color is (slightly) broken
DescriptionThe below range color feature is slightly broken. It is very, very probable that it is actually showing up a problem with Rescale to Data Range. Needs to get fixed. Basically, the minimum value on the color legend/ data range is very slightly too high. This use to just default to the lowest value, now it flips to the Below range color - color.

* Linux, master, local server.
* open disk_out_ref.exo. All vars on. Apply. Color by Temp.
* Open the color map editor. Turn on Use Below Range Color.
<<bug>> - You will see lots of black on the outside of the dataset. Note that this appears different (i.e., solid) and wrong on Windows.

TagsNo tags attached.
ProjectSandia
Topic Name
Typeincorrect functionality
Attached Files

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  Notes
(0034435)
Cory Quammen (developer)
2015-06-01 17:50

 Hi Alan,

I confirmed the black speckling pattern on linux and solid black coloring on Windows. I suspect the speckling is from numerical error in the texture coordinate interpolation performed in OpenGL when looking up the color from the color table.

The only quick solution I can think of at the moment involves subtracting an epsilon from the minimum range value, which you can do manually by using the "Rescale to custom range" button. The problem is that this is kind of a band-aid approach that doesn't eliminate the problem entirely - for example, you can add epsilon back to the minimum value using "Rescale to custom range" and you'll see the problem again.

Do your users often have data sets with large swaths of values near either end of the range? That should be the only time the speckling/wrong classification is visible.

Thanks,
Cory
(0034518)
Ken Moreland (manager)
2015-06-08 17:21

 This sounds like it might be a problem with how scalars are mapped to texture values when above/below range colors are enabled. Presumably, the scalar values in the [min,max] range map to texture coordinates [0,1]. But if you fill in the lower and upper texels in the texture, you need to adjust the range to map to texels second to the end. So, for example with a texture with 1024 entries, the scalars should map to coordinates [1/1024, 1 - 1/1024]. If ParaView is not doing that, then it is a bug.

If ParaView is already doing that and you are still getting the above/below range value for that value, then I suggest pushing the range in by a little bit. I would think half a texel should do it. So with the previous example, move in to [3/2048, 1 - 3/2048].
(0034519)
Cory Quammen (developer)
2015-06-08 17:26

 ParaView is indeed accounting for the out-of-range colors in the texture coordinate computation. See commit 238163f9ad8dda4870fe78d0a994f3b607d556eb in VTK for the change.

I'll try your suggestion for pushing in the range a bit if we see this behavior with the OpenGL2 backend.
(0038809)
Kitware Robot (administrator)
2016-08-12 09:59

 Resolving issue as `moved`.

This issue tracker is no longer used. Further discussion of this issue may take place in the current ParaView Issues page linked in the banner at the top of this page.

 Issue History
Date Modified Username Field Change
2015-04-29 16:55 Alan Scott New Issue
2015-04-29 16:55 Alan Scott Target Version => 4.4
2015-05-29 13:41 Utkarsh Ayachit Assigned To => Cory Quammen
2015-06-01 17:50 Cory Quammen Note Added: 0034435
2015-06-08 17:21 Ken Moreland Note Added: 0034518
2015-06-08 17:26 Cory Quammen Note Added: 0034519
2015-07-06 11:24 Utkarsh Ayachit Status backlog => todo
2015-07-08 16:30 Utkarsh Ayachit Status todo => backlog
2015-09-11 16:43 Utkarsh Ayachit Target Version 4.4 => 5.1
2016-08-12 09:59 Kitware Robot Note Added: 0038809
2016-08-12 09:59 Kitware Robot Status backlog => closed
2016-08-12 09:59 Kitware Robot Resolution open => moved

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