[Paraview] Colormap opacity / transparency

[Gary Strangman]

Hi Utkarsh,

Half-progress. So, I can display a variable-transparency volume rendering
(in this case of a head MRI, set so that the 0s around the head are
transparent). I can then add a .vtk surface, and I can sorta see "both"
datasets when opacity on the surface is set to 1.00 ... the grayscale volume
peeks through at various points of the overlying (colorized) surface. I'd
like to be able to see more of the underlying volume, so I reduce the
opacity value for the surface. However, for any opacity value < 1.00,
paraview renders only the /back/ side of the surface (the part of the
surface on the other side of the head from the camera viewpoint) ... the
foreground portion disappears completely. After playing around with
translations, I'd guess that for opacity<1.00 the volume is entirely
rendered last, overwriting what should be foreground surface pixels. Does
that make any sense? Perhaps I need to show a picture ...

-best
Gary


Gray,

Currently ParaView supports changing the opacity in colormaps only for
volume rendering. When rending slice or points as surface or anything
other than volume, opacity will be fixed to single value that can be
set on the Display tab.

Utkarsh

On Mon, Jun 20, 2011 at 4:30 PM, Gary Strangman
<gary.strangman at gmail.com> wrote:
> Hi again all,
> I solved my linked-colormap problem when rendering multiple volumes
(thanks
> Utkarsh, using separate variable names worked great!). My next issue is
> this: can someone explain when colormap transparency is enabled? In some
of
> my data views, the opacity option is grayed out (for example, in slice
> renderings, and also in points data). I kinda understand the points case,
> but I was surprised by slice renderings. I suspect there is an underlying
> principle I'm missing here ...
> -best
> Gary
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