[vtkusers] Distortions in Volumerendering in VR-Mode (HTC Vive)

[Ken Martin]

> Since the OpenVR interface is a little bit hackish within VTK the only
> thing that decides whether it renders for OpenVR or for normal 2D-Display
> is whether we link against vtkOpenVR and vtkRenderingOpenVR modules or not.
>
>

Ohh, actually that is a CMake option. If you turn VTK_OPENVR_OBJECT_FACTORY
off then the normal rendering is the default and you can explicitly create
OpenVR objects when/where you want them. Just make sure you create these 4
objects as the default factory will not create the OpenVR versions

vtkOpenVRRenderWindow
vtkOpenVRRenderer
ren->SetActiveCamera(a vtkOpenVRCamera)
renWin->SetInteractor(a vtkOpenVRRenderWindowInteractor);

and when using OpenVR you need to start the OpenVR interactor otherwise it
will not work. That is what I do for ParaView right now to support both on
screen and VR in the same executable.


> Everything code related is the same.
>
>
> So to reply to your Question:
>
> > Could you try rendering a volume with an identity matrix set as its
> transformation?
>
>
> I've build this simple program and it only places a volume dataset within
> the world without any transformation. The volume is directly given to the GPUVolumeRCMapper
> without any transformation. In "2D"-Renderwindow everything is fine. Also
> in anaglyph rendering I get a nice 3D View.
>
> But when I link against OpenVR module the view dependend distortions
> appear within VR. I've tried some things.
>
> All I can say is, that the errors appear if I look at any edge or corner
> of the surrounding (invisible) boundingbox around the rendered volume. If I
> look directly on one side of the boundingbox everything seems fine.
>
>
> The only thing I can imagine from this perspective is, that the GPUVolumeRCMapper
> gets wrong view directions for the eyes. But the vtkOpenVRCamera objects
> seems to do everything right.
>
>
> I don't know how to adjust the clipping box / bounding box you mentioned.
> Can you explain how I can do this, maybe this helps me to debug further?
>
>
> Sincerely,
>
> Sebastian
>
> ------------------------------
> *Von:* vtkusers <vtkusers-bounces at vtk.org> im Auftrag von Alvaro Sanchez <
> alvaro.sanchez at kitware.com>
> *Gesendet:* Mittwoch, 7. Dezember 2016 18:14
> *An:* polybos
> *Cc:* VTK Users
> *Betreff:* Re: [vtkusers] Distortions in Volumerendering in VR-Mode (HTC
> Vive)
>
> Hi,
>
> I have never tested the GPUVolumeRCMapper with OpenVR but as far as I
> remember Ken mentioned some time ago that he encountered a clipping/bbox
> related issue when adjusting the volume's orientation and position. Could
> you try rendering a volume with an identity matrix set as its
> transformation?,  this might give you a hint of what the mapper is doing
> wrong.
>
> Cheers,
> Alvaro
>
> On Wed, Dec 7, 2016 at 11:38 AM, polybos <franz at znarfsoft.de> wrote:
>
>> Sebastian Heerwald wrote
>> > If I look onto the volume rendering and move around it, there appear
>> > "refraction" lines.
>>
>> Unfortunately I cannot help with this issue but I would also be very
>> pleased
>> if someone could help here. Or did you, Sebastian, already achieve some
>> more
>> insights into this problem?
>> I also get such distortions on the HTC Vive when using
>> vtkVolumeRayCastMapper, while everything seems perfectly well in a
>> mesh-only
>> rendering.
>>
>> Does anyone have similar issues? Maybe with Occulus Rift? As far as I
>> understand Sebastian just test with a HTC Vive. At least I can only test
>> with a HTC Vive.
>>
>>
>>
>> --
>> View this message in context: http://vtk.1045678.n5.nabble.c
>> om/Distortions-in-Volumerendering-in-VR-Mode-HTC-Vive-
>> tp5741338p5741457.html
>> Sent from the VTK - Users mailing list archive at Nabble.com.
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>
>
>
> --
> Alvaro Sanchez
> Kitware, Inc.
> Senior R&D Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4901
>
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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971

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