[vtkusers] Volume + surface transparency with OpenGL2

[Marcus D. Hanwell]

We have also had a number of tomviz users ask if this is possible, and
they have similar requirements to those stated above. We often have
the overall structure rendered as a volume, and are looking at
distinct isosurfaces, or in future segmented features, where the ideal
would be to offer a translucent surface within the volume.

On Mon, Nov 23, 2015 at 7:05 PM, David Cole via vtkusers
<vtkusers at vtk.org> wrote:
> Me too.
>
> We want to visualize structures (natural and artificial) inside of volume
> renderings of CT scans, mostly of people.
>
> Works great without using translucent polydata. As soon as you make any of
> it translucent, it just sort of disappears all the way... Very confusing
> when you first encounter it.
>
> So... +1. And let me know what I can do to test/help out...
>
>
> David C.
>
>
>
> On Monday, November 23, 2015, Xabi Riobe <xabivtk at gmail.com> wrote:
>>
>> Here are at least 2 examples:
>>
>> - medical data : the body is voxelized and you have the segmentation of
>> organs/bones/vessels
>> - material : cement, rock structure voxelized, with segmentation of the
>> different layers, components
>>
>> in both cases you may want to superimpose the surfaces and play with
>> transparency to highlight an entity but still seeing the inside of it,
>> or you can have tools with polygonal surface that you will insert in an
>> easier way into the volume if they are transparent, or just a clipping plane
>> that you want to be transparent to place it with precision inside the volume
>> before doing the clip...
>>
>> I'm glad to hear it may fit in a todo list :)
>> Let me know if someone starts working on this, i may give any kind of help
>> !
>>
>> Thanks
>>
>>
>> 2015-11-23 21:40 GMT+01:00 Aashish Chaudhary
>> <aashish.chaudhary at kitware.com>:
>>>
>>> On Mon, Nov 23, 2015 at 3:14 PM, Xabi Riobe <xabivtk at gmail.com> wrote:
>>>>
>>>> Hi Aashish,
>>>>
>>>> For example, if you render a volume with vtkGPUVolumeRayCastMapper, or
>>>> vtkFixedPointVolumeRayCastMapper, and you put inside a sphere rendered with
>>>> vtkPolyDataMapper, as soon as you change the sphere actor opacity the depth
>>>> notion is lost, with the sphere appearing behind the volume.
>>>
>>>
>>> Thanks for clarification. Yes, this is not currently supported (I am not
>>> aware and we don't handle this in the mapper). This is a interesting use
>>> case. I will add it to the feature request and will get back to you. Just
>>> curious, what would be a real world example use-case you have for this
>>> feature? Can you share bit more domain information (medical / scientific
>>> etc.).
>>>
>>> - Aashish
>>>
>>>
>>>
>>> --
>>> | Aashish Chaudhary
>>> | Technical Leader
>>> | Kitware Inc.
>>> | http://www.kitware.com/company/team/chaudhary.html
>>
>>
>
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