[Paraview] question about color mapping

[David E DeMarle]

The rescale automatically behaviour is good for emphasizing relative
differences within a single image.

However it is bad for showing absolute values. In the example I gave
before, if you see the two images side by side, you naturally assume
that red areas in both pictures are similar when they are not. So if
you stick with the default, or better yet specify your own range, you
always know what each color means.

David E DeMarle
Kitware, Inc.
R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909


On Thu, Jun 28, 2012 at 3:21 PM, Tom Schoenemann <toms at indiana.edu> wrote:
> Good, OK. So if I use "Rescale Range" and set every file to, say, -10 to 10
> (regardless of the underlying scalar values they might have), then color
> differences between these various files would truly indicate differences
> between them for the underlying scalar values?
>
> -Tom
>
> On Jun 28, 2012, at 3:49 PM, David E DeMarle wrote:
>
> It doesn't affect the scalars themselves, just the colors that are
> assigned to them.
>
> Say you use a red to green to blue color map, with red corresponding
> to -10 and green corresonding to 0 and blue corresponding to 10.
>
> Say you apply some filter or step to another timestep and your new
> data values change from having a range of -10 to 10 to a new range of
> 9 to 10. All the data now looks blue.
>
> If you click rescale to color range, the data that has a value of 9
> will now look red instead and you will see all the colors along the
> map.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4909
>
>
> On Thu, Jun 28, 2012 at 2:25 PM, Tom Schoenemann <toms at indiana.edu> wrote:
>
> In the "Edit Color Map" section of the display, one of the options is to
>
> "Rescale Range". Hovering over it with the mouse it says: "Click this button
>
> to rescale the color map to a new range"
>
>
> Does this mean that, e.g., if my scalar values go from 2 to 10, and I use
>
> this "Rescale Range" option to have a minimum of 3 and a maximum of 9, does
>
> Paraview literally rescale the values, so that 2 now becomes 3, 10 now
>
> becomes 9, and all the intermediate values are similarly shifted?  Or does
>
> this mean that every value between 2 and 3 now gets colored the same as 3,
>
> and everything between 9 and 10 gets colored the same as 9?
>
>
> In other words, are the scalar values being compressed, or just truncated,
>
> with respect to the colors?
>
>
> Thanks for any clarification,
>
>
> -Tom
>
>
> _________________________________________________
>
> P. Thomas Schoenemann
>
>
> Associate Professor
>
> Department of Anthropology
>
> Indiana University
>
> Bloomington, IN  47405
>
> Phone: 812-855-8800
>
> E-mail: toms at indiana.edu
>
>
> Open Research Scan Archive (ORSA) Co-Director
>
> Consulting Scholar
>
> Museum of Archaeology and Anthropology
>
> University of Pennsylvania
>
>
> Homepage: http://mypage.iu.edu/~toms/
>
>
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> _________________________________________________
> P. Thomas Schoenemann
>
> Associate Professor
> Department of Anthropology
> Indiana University
> Bloomington, IN  47405
> Phone: 812-855-8800
> E-mail: toms at indiana.edu
>
> Open Research Scan Archive (ORSA) Co-Director
> Consulting Scholar
> Museum of Archaeology and Anthropology
> University of Pennsylvania
>
> Homepage: http://mypage.iu.edu/~toms/
>
>
>
>
>
>
>
>
>