[vtkusers] EyePosition / EyeTransform, GPU Volume Rendering, and Off-Axis Projection

[Aashish Chaudhary]

Hi,

Very nice.. Could you please send me the patch?

Thanks,


On Fri, Jul 6, 2012 at 5:24 PM, Krzysztof Kamieniecki
<krys at kamieniecki.com> wrote:
> I have a patch available (i'm not sure where to send it). I changed
> vtkCamera and vtkOpenGLGPUVolumeRayCastMapper to produce and expect
> GetEyePosition() to give the actual eye position in world space. This seems
> to fix my problem. I think there may still be a clipping issue because of
> the use of GetEyePlaneNormal in vtkRenderer. I have to fix some of my own
> code to get more testing done and I would like to hear more about the
> original intent of EyePosition before making any more changes.
>
> On Fri, Jul 6, 2012 at 1:54 PM, Krzysztof Kamieniecki <krys at kamieniecki.com>
> wrote:
>>
>> Hi Aashish,
>>
>> I would like to try to take a stab at it.
>>
>> Based on the only use of GetEyePosition in VTK it seems like
>> GetEyePosition should return the world space positions. (This expectation
>> also explains the problems I have been seeing with weird clipping)
>>
>> from vtkRenderer::ResetCameraClippingRange
>> ...
>>   if(!this->ActiveCamera->GetUseOffAxisProjection())
>>     {
>>     this->ActiveCamera->GetViewPlaneNormal(vn);
>>     this->ActiveCamera->GetPosition(position);
>>     this->ExpandBounds(bounds,
>> this->ActiveCamera->GetModelTransformMatrix());
>>     }
>>   else
>>     {
>>     this->ActiveCamera->GetEyePosition(position);
>>     this->ActiveCamera->GetEyePlaneNormal(vn);
>>     this->ExpandBounds(bounds,
>> this->ActiveCamera->GetModelViewTransformMatrix());
>>     }
>> ...
>>
>> My current understanding is that the OffAxisProjection perspective
>> transformation matrix is being used by the GPU Renderer to setup to outer
>> polygons.
>>
>> So the main thing to do would be to produce world coordinate Eye Positions
>> and use those instead of the Camera Position in the volume Renderer, so the
>> shaders would get the proper ray directions?
>>
>> What is the desired functionality of EyeTransform? WorldToEye, EyeToWorld,
>> CameraToEye, EyeToCamera?
>>
>> Best Regards,
>> Krys
>>
>> On Fri, Jul 6, 2012 at 1:41 PM, Aashish Chaudhary
>> <aashish.chaudhary at kitware.com> wrote:
>>>
>>> Hi Krzysztof,
>>>
>>> On Fri, Jul 6, 2012 at 1:12 PM, Krzysztof Kamieniecki
>>> <krys at kamieniecki.com> wrote:
>>> > Hi,
>>> >
>>> > How is the EyePosition and EyeTransform functionality supposed to
>>> > behave,
>>> > should the positions be in CameraSpace or WorldSpace?
>>> >
>>> > Should they be syncronized with EyeSeparation / LeftEye when in
>>> > Off-Axis
>>> > Projection mode?
>>>
>>> >
>>> > I am trying to get the GPU Volume renderer to work with Stereo 3D in
>>> > Off-Axis projection mode, one problem seems to be that the Camera
>>> > position
>>> > is used instead of the Eye position.
>>>
>>> This is a known problem and based on my prior discussions with volume
>>> rendering experts here at Kitware, I believe that this needs to be
>>> fixed on the volume rendering side of things.
>>> If you want to make it work by yourself then we could provide you
>>> guidance for this task.
>>>
>>> Thanks,
>>>
>>>
>>>
>>> >
>>> > Thanks,
>>> > Krys
>>> >
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>>>
>>>
>>>
>>> --
>>> | Aashish Chaudhary
>>> | R&D Engineer
>>> | Kitware Inc.
>>> | www.kitware.com
>>
>>
>
>
> _______________________________________________
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>
> Visit other Kitware open-source projects at
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>
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-- 
| Aashish Chaudhary
| R&D Engineer
| Kitware Inc.
| www.kitware.com