[Paraview] Volume Rendering with opacity mapping and specular highlights

[Aashish Chaudhary]

On Wed, Sep 23, 2015 at 3:34 PM, Mathew Guilfoyle <mrguilfoyle at gmail.com>
wrote:

> Aashish - thanks for the reply
>
> I am using the latest OS X binary download (4.4.0) - is this OpenGL2?
> When I switch ‘Volume Rendering Mode’ to GPU rendering all images disappear
> so I presume I’m only able to use CPU rendering.  I am on a 2014 Macbook
> Pro with Nvidia GT750M.
>

No it would be OpenGL old version VTK. It would be nice if you can try
OpenGL2 version although I don't think your problem is related to GL
version.

>
> I’m using contrast enhanced volumetric CT imaging.  I want to render blood
> vessels in red; within the scan they appear in approximately the 100-200
> Hounsfield unit range. The full range of scalar data is [-1024, 3071]. On
> this basis I’ve set up the following colour and opacity mappings:
>
> Colour:
> Value R-G-B
> -1024 0-0-0
> 99 0-0-0
> 100 1-0-0
> 200 1-0-0
> 201 0-0-0
> 3071 0-0-0
>
> Opacity:
> Value Opacity
> -1024 0
> 99 0
> 100 1
> 200 1
> 201 0
> 3071 0
>
> None of the voxels appear to be fully opaque in the rendering.  When I
> increase the specular from 0 to 1 it has no effect at all on the image.
>
> Have you enabled the lighting?
http://www.vtk.org/doc/nightly/html/classvtkVolumeProperty.html (ShadeOn)
on volume property?

- Aashish


> Ideally, I would want to emulate something along the lines of this:
> http://www.cemuva.com/img/uploads/malformacion-arteriovenosa-cerebral-3d.jpg
>
> Again, cheers for the help
> Mathew
>
> On 23 Sep 2015, at 18:24, Aashish Chaudhary <aashish.chaudhary at kitware.com>
> wrote:
>
> Matthew,
>
> * Can you send us the exact number you are putting in for the transfer
> function? Make sure that you have values for the entire range of scalar
> values?
>
> * Are you using OpenGL2 version?
>
> - Aashish
>
> On Wed, Sep 23, 2015 at 1:18 PM, Mathew Guilfoyle <mrguilfoyle at gmail.com>
> wrote:
>
>> Thanks for the suggestions.  After looking into it further the type of
>> visualisation I am after is volume rendering of the data with an opacity
>> transfer function based on the scalar data values.
>>
>> I have set up my volume rendering to have full (i.e =1) opacity through
>> the range of scalar values I’m interested in, reducing to near transparency
>> either side of this.  I also want specular highlighting of the opaque
>> tissues.
>>
>> However, despite these settings Paraview does not seem to render any
>> voxels as fully opaque and there is certainly no specular highlighting.  Is
>> this a known limitation?
>>
>> Many thanks
>>
>> On 21 Sep 2015, at 15:10, David E DeMarle <dave.demarle at kitware.com>
>> wrote:
>>
>> Two suggestions:
>> * try contour filter instead of threshold if contour isn't available,
>> apply cell to point first.
>> * try the clip filter with the clip type set to scalar.
>> hth
>>
>> David E DeMarle
>> Kitware, Inc.
>> R&D Engineer
>> 21 Corporate Drive
>> Clifton Park, NY 12065-8662
>> Phone: 518-881-4909
>>
>> On Mon, Sep 21, 2015 at 9:40 AM, Mathew Guilfoyle <mrguilfoyle at gmail.com>
>> wrote:
>>
>>> I would be grateful for some advice on volume and surface rendering in
>>> Paraview.
>>>
>>> I am trying to generate 3D skull models from CT data.  The reason for
>>> using Paraview is to take advantage of the detailed fly-through/movie
>>> capability.  I can generate an acceptable 3D model that I can interact with
>>> in OsiriX and 3D Slicer, both of which I believe use VTK.  However, in
>>> Paraview I am struggling to create a 3D model that looks any good.
>>>
>>> When I apply a threshold filter and view as a ‘Surface’ the image is a
>>> lot more ‘blocky’ than in the other two applications.  The image is
>>> dominated by the artifactual lines due to the original data being acquired
>>> as axial slices; whereas in OsiriX and 3D Slicer this gets smoothed out and
>>> the ‘genuine’ surface skull features (sutures etc) stand out.
>>>
>>> I realise this is probably question of apply the correct series of
>>> filters and that the other two apps do this ‘under the hood’.  However, i
>>> have tried to apply Decimation and Smooth to the extracted surface and am
>>> not making any headway.
>>>
>>> Any pointers would be very welcome
>>>
>>> M
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>>
>>
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>
>
> --
>
>
>
> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.            *
> *| http://www.kitware.com/company/team/chaudhary.html
> <http://www.kitware.com/company/team/chaudhary.html>*
>
>
>


-- 



*| Aashish Chaudhary | Technical Leader         | Kitware Inc.            *
*| http://www.kitware.com/company/team/chaudhary.html
<http://www.kitware.com/company/team/chaudhary.html>*
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