[Paraview] How to do volume rendering of image data?

[Moreland, Kenneth]

The data you sent has RGB values but no alpha values that I can see.  Volume rendering is generally not very useful if you do not have some representation of opacity.  If you were to assume a homogeneous opacity, you would get a mostly black box with a blob of color in the middle if you looked hard enough.  How exactly you expect the volume renderer to behave?

-Ken


On 7/18/10 2:43 AM, "Steve Huntley" <stephen at xhuntley.net> wrote:

Attached is a small sample vtk file that illustrates the problem. It is
a rough representation of a human molar composed originally of 13 jpeg
image slices, processed into a raw file with ImageJ, then saved to vtk
by Paraview.

When I open the file in Paraview 3.2 I see a black block when I choose
volume representation. The information tab describes it as a uniform
rectilinear grid and shows number of points and cells, just like the
info tab of the sample wavelet object described by Utkarsh does.

When I open it in Paraview 3.8, the statistics entries in the
information tab are blank, and when I try to choose volume
representation I get the error mentioned below.

Utkarsh, I'm not sure what you mean by "single component point scalars."
Does this mean that color images with three scalar RGB values per grid
node can't be volume rendered? If so, does that mean that what I'm
currently attempting is impossible in Paraview? Or is there a way to
hack RGB color information into single-value scalars and render a color
3D image?

Moreland, Kenneth wrote:
> Nope. ParaView is just telling you that the current operation is not
> supported.
>
> Probably the best course of action is to submit a feature request to
> ParaView's bug list (http://www.paraview.org/Bug) to which you can
> attach an example file. I would also recommend entering the feature in
> uservoice (http://paraview.uservoice.com/forums/11350-general). The
> ParaView developers use this site to determine the priority of
> suggested features.
>
> If you have an example data set that is not too big, you can email it
> to the mailing list or directly to me and I can do these for you.
>
> -Ken
>
>
> On 7/17/10 2:38 AM, "Steve Huntley" <stephen at xhuntley.net> wrote:
>
>     Up to now I have been working with version 3.2. I just installed
>     version 3.8 to see if there were any differences in behavior.
>
>     In version 3.8 I'm not allowed to do volume rendering at all. When I
>     try to set the "Volume" representation option (which resulted in
>     display
>     of a black block in 3.2), I now get an error message that says "Cannot
>     volume render since no point (or cell) data available."
>


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