[vtkusers] Re: RGBA data set volume rendering

[Yi-Yu Chou]

Hi,
But according to the vtk document, we just need to set the method
"IndependentComponentsOff" for the vtkVolumeMapper.
In this way, for 4 component data, the first three will directly
represent RGB (no lookup table). The fourth component will be passed
through the first scalar opacity transfer function for opacity. Isn't
it ???

On Thu, 23 Sep 2004 11:49:11 +0300, Dr. Daniel James White PhD
<dan at chalkie.org.uk> wrote:
> Hi,
> 
> As  understand it,
> the VTK volume mappers are not able to render a RGBA data set, since
> the mappers only read a single scalar value for each voxel/point.
> In a RGBA volume there are of course 3.
> 
> (Yi-Yu, in your case you have to use the vtk  image liminance filter to
> essentially turn the RGBA volume into grayscale, single gray scale
> values for each voxel, then volume render)
> 
> I would also love to have a raycast/shearwarp/2Dtexturemapper that
> handles RGBA data, or RGB data with a user definable opacity transfer
> function.
> I have  a programming student who has this on his to do list. Our
> microscopy data is RGB tiff image stacks, and it would be great to
> volume render in "real" colour.
> 
> Is there anyone out there who has already done this?
> 
> Wouldn't the code be very similar to the existing ray cast mapper,
> only the ray would pick up the RGB colour as it passes through the
> volume,
> so there would be no colour transfer function?
> There could be a window level type contrast/brightness control to
> adjust the appearance of the rendering.
> And you could either use the alpha channel for opacity, or use a user
> defined LUT(opacity transfer function.
> 
> I have  volume pro 1000 board, and I think this kind of data is
> supported by the volume pro driver vli3 library and the board,
> but not in the vtk code for accessing the vli3 library. Is this
> correct... rtviz folks?
> 
> Anyone have any ideas or existing code?
> 
> cheers
> Dan
> 
> Message: 3
> Date: Wed, 22 Sep 2004 13:51:30 -0400
> From: Yi-Yu Chou <yiyu.chou at gmail.com>
> Subject: [vtkusers] Volume Rendering for 4 Compoents Image ~ HELP !!!!
> To: vtkusers at vtk.org
> Message-ID: <8c82113e040922105136f440aa at mail.gmail.com>
> Content-Type: text/plain; charset=US-ASCII
> 
> Dear vatkusers:
> 
> I am trying to display a 4 components image under Python with VTK4.2.
> I used the following code to do the volume rendering, but I only got a
> black box.
> 
>                compositeFunction = vtkVolumeRayCastCompositeFunction()
>                volumeMapper = vtkVolumeRayCastMapper()
>                volumeMapper.SetVolumeRayCastFunction(compositeFunction)
>                volumeMapper.IndependentComponentsOff()
>                volumeMapper.SetInput(image) ## image is a 4-component vtkImageData
> 
>                 opacityTFunc = vtkPiecewiseFunction()
>                opacityTFunc.AddPoint(0,0)
>                opacityTFunc.AddPoint(255,255)
> 
>                volumeProperty = vtkVolumeProperty()
>                volumeProperty.SetScalarOpacity(opacityTFunc)
> 
>                self.volume = vtkVolume()
>                self.volume.SetMapper(volumeMapper)
>                self.volume.SetProperty(volumeProperty)
> ........................................................................
> ............................................
> 
> Any help is appreciated in advance !!!!!!!
> 
> Dr. Daniel James White BSc. (Hons.) PhD
> Cell Biology, Ambiotica C242
> Department of biological and environmental science
> PO Box  35
> University of Jyväskylä
> Jyväskylä FIN 40014
> Finland
> +358 14 260 4183 (work)
> +358 468102840 (mobile)
> 
> http://www.chalkie.org.uk
> dan at chalkie.org.uk
> white at cc.jyu.fi
>