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Volume mapper bug on negative values with unstructured grids

Negative values when volume rendering an unstructured grid doesn't display correctly.

In the following screenshot, all visualizations should be identical, as the only difference between them is a scalar shift. They all have independent scalar bars. Top left view has only positive values (and displays correctly), and bottom right view has all values bellow the "white color" that are negative.

image

Here's a state file to get the state of this screenshot: volume_mapper_bug.pvsm

I am using Hyper Tree Grids in this example because they are an easy way to produce an unstructured grids without loading a file.

To reproduce locally:

  • Sources -> Data Objects -> Hyper Tree Grid (Random)
  • Inside the Properties panel, set Split Fraction to 0.15.
  • Filters -> Hyper Tree Grids -> HyperTreeGrid To UnstructuredGrid
  • Calculator1 : Depth - 1
  • Calculator2 : Depth - 2
  • Calculator3 : Depth - 3
  • Create 4 views
  • View top left : volume render output of filter
  • View top right : volume render Calculator1
  • View bottom left : volume render Calculator2
  • View bottom right : volume render Calculator3

For each view, click Use Separate Color Map

For each view, click Rescale To Data Range

For each color map, cancel red and white, and amplify blue.

Note that volume visualization work correctly on image data (so shifting the scalar fields of the Wavelet Source so there are negative values will work).

Edited by Yohann Bearzi (Kitware)
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