[vtkusers] Problem with volume rendering and 2 independent components

Lisa Avila lisa.avila at kitware.com
Wed Jun 22 11:21:57 EDT 2005

Hi Jef,

OK - what you are doing is treating the components are two independent 
components, with two separate color/opacity mappings. That is supported by 
the vtkFixedPointVolumeRayCastMapper only - so you'll need to use that 
mapper. Maybe that is the problem?


At 10:18 AM 6/22/2005, Jef Driesen wrote:

>Maybe mapping components to hue or value directly is not supported. But 
>what I did was create a different color transfer function for each 
>component, where only the hue (or value depending on the component) is 
>changed during the interpolation. And for the opacity transfer function I 
>used a lineair ramp for both components. Just like I did in volview (or 
>maybe not?).
>Maybe it is easier to explain my problem with some pictures. I have 
>uploaded them to 
><http://users.telenet.be/sacn/vtk/>http://users.telenet.be/sacn/vtk/. The 
>file 'volume-uint16.img' is my dataset. When I load the file in volview 
>(with the parameters of the *.vvi and *.vti files), the result is 
>something like the screenshot 'volview.png'. And I want to create a 
>similar result with the vtk filters.
>If I render each components separatly with vtk, I can obtain the desired 
>result. The 'volume-avg.png' and 'volume-std.png' are screenshots of the 
>renderings of respectively the first and second component of the dataset. 
>And those result are almost identical to those of volview (created by 
>setting the component weight to 1.0 and the other one to 0.0). But it 
>seems inpossible to combine those images, e.g. I get garbage like in the 
>'volume.png' screenshot.
> >From: Lisa Avila <lisa.avila at kitware.com>
> >To: "Jef Driesen" <jefdriesen at hotmail.com>, vtkusers at vtk.org
> >Subject: Re: [vtkusers] Problem with volume rendering and 2 
> independent  components
> >Date: Wed, 22 Jun 2005 09:47:28 -0400
> >
> >Hi Jef,
> >
> >I am not sure how loading the data into VolView is producing "the
> >expected results" - VolView (and therefore the mappers in VTK) does
> >not support mapping the first component to value and the second to
> >hue. What you can do is map the first component to hue (or any hsv
> >or rgb colormap) and the second to opacity. This can be done with
> >the vtkFixedPointVolumeRayCastMapper and the
> >vtkVolumeTextureMapper3D. The other volume mappers only support one
> >component data.
> >
> >Lisa
><http://g.msn.com/8HMAENBE/2728??PS=47575>Free blogging with MSN Spaces !
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