[vtkusers] Multiple volumes rendering with vtkGPUVolumeRayCastMapper or similar

Elvis Stansvik elvis.stansvik at orexplore.com
Mon Aug 29 07:36:25 EDT 2016 

2016-08-29 13:17 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:

> 2016-08-28 2:10 GMT+02:00 Alvaro Sanchez <alvaro.sanchez at kitware.com>:
>
>> Sounds good, let us know if you still encounter the same issue with your
>> proper
>>
> I just made another test, and indeed rendering of two volumes seems to
> work.
>
> However, if you look at the attached short screencast (two_volumes.ogv),
> where I move the camera around such that one volume is in front of the
> other, the volume that is in the back is not visible, instead the
> background color (white) is shown in this area.
>
> Any idea what is going on here? I would have expected to be able to see
> the other volume through the first one. (The volumes in this screencast are
> not intersecting eachother).
>

To give more details: In this example, it's two vtkVolumes, each have their
own vtkGPUVolumeRayCastMapper and vtkVolumeProperty, but they're added to
the same vtkRenderer. I've also tried having them share the same mapper and
property, but the result is the same.

Must I do something with layers on the vtkRenderer? Or is there some
setting to activate alpha channel on the volumes?

Elvis


> Thanks in advance,
> Elvis
>
>
>>
>> On Aug 26, 2016 12:59 PM, "Elvis Stansvik" <elvis.stansvik at orexplore.com>
>> wrote:
>>
>>> 2016-08-26 14:15 GMT+02:00 Alvaro Sanchez <alvaro.sanchez at kitware.com>:
>>>
>>>> Indeed Elvis, to clarify the confusion, I was referring to overlapping
>>>> volumes in my last email. As mentioned in (
>>>> http://public.kitware.com/pipermail/vtkusers/2016-February/094333.html),
>>>> it is possible to add multiple vtkVolumes to a single vtkRenderer, this
>>>> would work if they are not overlapping.
>>>>
>>>> >Would the obstructed voxels of the >furthest volume not be visible at
>>>> all, or >would I be able to see them "through" >the nearest volume?
>>>>
>>>> You should see through (alpha blending is on during volume rendering).
>>>>
>>> Thanks for clarifying Alvaro, that's reassuring. I did make a quick test
>>> with two volumes before I left work today and couldn't get the second one
>>> to show up, but it's quite likely I made something wrong since I was in a
>>> rush. I'll make a proper test when I'm back at work on Monday.
>>>
>>> Elvis
>>>
>>>
>>>> On Aug 26, 2016 3:04 AM, "Elvis Stansvik" <elvis.stansvik at orexplore.com>
>>>> wrote:
>>>>
>>>>> 2016-08-26 8:38 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com
>>>>> >:
>>>>>
>>>>>> Den 26 aug. 2016 5:06 fm skrev "Alvaro Sanchez" <
>>>>>> alvaro.sanchez at kitware.com>:
>>>>>> >
>>>>>> > Hi Alberto,
>>>>>> >
>>>>>> > as you have noticed, multi-volume rendering is currently not
>>>>>> supported in the vtkGPUVolumeRayCastMapper.  If you are building VTK with
>>>>>> OpenGL2 however, it supports independent components so (depending on your
>>>>>> use case) you might be able to render up to 4 volumes (one per component),
>>>>>> provided you can arrange them in a four component array (this has the
>>>>>> limitation that each component will need to have the same dimensions).
>>>>>> That said, we are working on giving support for multiple volumes in the
>>>>>> next VTK release.
>>>>>>
>>>>>> I have to jump in and ask: I was under the impression that multiple
>>>>>> volumes was supported, as long as they don't intersect eachother in 3D
>>>>>> space? But you're saying it's not possible at all?
>>>>>>
>>>>> I found the mail by Aashish which led me to believe this was possible:
>>>>>
>>>>>     http://public.kitware.com/pipermail/vtkusers/2016-February/0
>>>>> 94333.html
>>>>>
>>>>> If it is actually possible, I have a question about the result I would
>>>>> get: If I had multiple volumes in the same view (non-intersecting) and the
>>>>> camera was positioned such that one of the volumes is in front of the other
>>>>> relative to the camera. Would the obstructed voxels of the furthest volume
>>>>> not be visible at all, or would I be able to see them "through" the nearest
>>>>> volume?
>>>>>
>>>>> Elvis
>>>>>
>>>>>
>>>>>> If so I'm in a bit of trouble myself, as I was planning on doing that
>>>>>> soon :(
>>>>>>
>>>>>> In my case I have multiple volumes (coming from different readers)
>>>>>> that I want to render next to eachother (but not overlapping anywhere).
>>>>>>
>>>>>> If that's really not possible, I'll have to rethink my pipeline and
>>>>>> redesign my custom reader to work with multiple files instead (and output a
>>>>>> single volume). The problem with this is that I might want to show a volume
>>>>>> that is larger than 2048 voxels in one dimension, which is not possible, at
>>>>>> least not on intel, due to GPU texture size limitations (see my semi-recent
>>>>>> thread about this). I had hoped that using multiple volumes would be a way
>>>>>> to get around this.
>>>>>>
>>>>>> Thanks in advance,
>>>>>> Elvis
>>>>>>
>>>>>> >
>>>>>> > With regards to the solution you mentioned (
>>>>>> https://github.com/bozorgi/VTKMultiVolumeRayCaster), you could use
>>>>>> it temporarily if it would solve your problem better than fitting the
>>>>>> volumes as independent components.  It seems to implement a similar
>>>>>> approach as we would do (connecting various inputs/ properties to the
>>>>>> mapper) so it should not be extremely difficult to migrate to the official
>>>>>> implementation in the future.  I have not tried it myself but please do let
>>>>>> us know if you have any remarks once you try it.  As far as I know, if the
>>>>>> python bindings are not explicitly disabled for these new classes then they
>>>>>> should be also wrapped.
>>>>>> >
>>>>>> > Regads,
>>>>>> > Álvaro
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> >>
>>>>>> >> ---------- Forwarded message ----------
>>>>>> >> From: amdelaossa <adelaossa at gmail.com>
>>>>>> >> Date: Thu, Aug 25, 2016 at 10:00 AM
>>>>>> >> Subject: [vtkusers] Multiple volumes rendering with
>>>>>> vtkGPUVolumeRayCastMapper or similar
>>>>>> >> To: vtkusers at vtk.org
>>>>>> >>
>>>>>> >>
>>>>>> >> Dear all,
>>>>>> >> we (a research team in DESY, Germany) are strongly interested in
>>>>>> rendering multiple data volumes in the same view with VTK.
>>>>>> >> We chose VTK for our 3D visualisation project on beam-plasma
>>>>>> interactions due to its extended functionality and features,
>>>>>> >> its open source character and because it is written in C++ with
>>>>>> bindings for python.
>>>>>> >> However, we will require to show multiple volumes in the same view
>>>>>> (representing the data of different particle species in our simulations).
>>>>>> >> We are currently using a vtkGPUVolumeRayCastMapper object for each
>>>>>> data set, which is then connected to a vtkVolume.
>>>>>> >> The different vtkVolume objects are then added to the vtkRenderer.
>>>>>> >> We have tried to use different vtkRenderer objects for the
>>>>>> different vtkVolumes,
>>>>>> >> but still only the first volume on the first vtkRenderer is
>>>>>> displayed.
>>>>>> >>
>>>>>> >> Searching in the web, we have found the following (potential)
>>>>>> solution:
>>>>>> >> https://github.com/bozorgi/VTKMultiVolumeRayCaster
>>>>>> >> which is published here:
>>>>>> >> http://www.ncbi.nlm.nih.gov/pubmed/24841148
>>>>>> >>
>>>>>> >> It consists on new vtk classes to handle multiple volumes
>>>>>> rendering.
>>>>>> >> As it might work well for our purposes, we would like to ask your
>>>>>> opinion about this new classes.
>>>>>> >> Are you planning to incorporate something like this in the
>>>>>> official VTK distribution soon?
>>>>>> >> If not, we will be interested in incorporating this new class into
>>>>>> our personal VTK installation.
>>>>>> >> Then the question is: Will be the python bindings automatically
>>>>>> generated for these new classes?
>>>>>> >>
>>>>>> >> Thanks a lot for your support!
>>>>>> >>
>>>>>> >> Best regards,
>>>>>> >> Alberto
>>>>>> >>
>>>>>> >>
>>>>>> >> _______________________________________________
>>>>>> >> Powered by www.kitware.com
>>>>>> >>
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>>>>>> >>
>>>>>> >> Please keep messages on-topic and check the VTK FAQ at:
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>>>>>> >>
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>>>>>> >>
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>>>>>> >>
>>>>>> >>
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > --
>>>>>> > Alvaro Sanchez
>>>>>> > Kitware, Inc.
>>>>>> > Senior R&D Engineer
>>>>>> > 21 Corporate Drive
>>>>>> > Clifton Park, NY 12065-8662
>>>>>> > Phone: 518-881-4901
>>>>>> >
>>>>>> > _______________________________________________
>>>>>> > Powered by www.kitware.com
>>>>>> >
>>>>>> > Visit other Kitware open-source projects at
>>>>>> http://www.kitware.com/opensource/opensource.html
>>>>>> >
>>>>>> > Please keep messages on-topic and check the VTK FAQ at:
>>>>>> http://www.vtk.org/Wiki/VTK_FAQ
>>>>>> >
>>>>>> > Search the list archives at: http://markmail.org/search/?q=vtkusers
>>>>>> >
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>>>>>> >
>>>>>>
>>>>>
>>>>>
>>>
>
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