Volume visualization with OpenVR

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Volume visualization with OpenVR

Carlos Lopez
Hello,

I'm visualizing a dataset from the visible human project using openVR and I notice that when the camera is outside of the bounds of the dataset, the data renders in a way that the bounding box is noticeable; because of the stereo projection, It is possible to see that the volumetric data is projected onto the faces of the bounding box (this is not visible in 2D, either from a monitor or if I close one eye in the HMD).

If the camera is inside the bounding box, then the data renders in a way that this effect is no longer visible, the projection plane parallel to the current view removes the small discontinuity and the 3D perspective is restored.

Is it possible to configure the volume rendering so that it always behaves as if the camera is inside the dataset?

thanks,
carlos


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Re: Volume visualization with OpenVR

Aashish Chaudhary-2
Hi Carlos, 

Can you send a picture of the effect you are mentioning? We have a demo that uses VR in OpenVR but we didn't notice the artifact that you have mentioned but we also have not spent as much time as you did. 

- Aashish

On Mon, May 15, 2017 at 11:42 AM Carlos Lopez <[hidden email]> wrote:
Hello,

I'm visualizing a dataset from the visible human project using openVR and I notice that when the camera is outside of the bounds of the dataset, the data renders in a way that the bounding box is noticeable; because of the stereo projection, It is possible to see that the volumetric data is projected onto the faces of the bounding box (this is not visible in 2D, either from a monitor or if I close one eye in the HMD).

If the camera is inside the bounding box, then the data renders in a way that this effect is no longer visible, the projection plane parallel to the current view removes the small discontinuity and the 3D perspective is restored.

Is it possible to configure the volume rendering so that it always behaves as if the camera is inside the dataset?

thanks,
carlos

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Re: Volume visualization with OpenVR

Carlos Lopez
Hi Aashish,

vtk is 7.1.1 with SHA:
b86da7eef93f75c4a7f524b3644523ae6b651bc4

the exact dataset I'm using is custom, but the issue might be the same with any volumetric imagedata.

best,
carlos



On Mon, May 15, 2017 at 2:48 PM, Aashish Chaudhary <[hidden email]> wrote:
Thanks for the images Carlos. Could you please send us the exact SHA/Version of VTK and also if you can point to the dataset (I know where it is but just in case). 

We have fixed a related view-clipping issue and since then we have not find any issues. It is possible that 1) There is a bug 2) This is related to perception since one eye is inside and the other is outside. 

- Aashish

On Mon, May 15, 2017 at 12:52 PM Carlos Lopez <[hidden email]> wrote:
Hi Aashish,

Here are the screenshots.

In external.png, notice how the arm is being rendered differently for this particular angle; in the HMD I get the sense there is a sharp edge along the arm.

When the camera is close enough, the mode of projection changes, and it looks like internal.png; here I do not see any edges and the 3D effect feels better to me.

In the transition, for very specific points of view, I get the in-between.png picture.

I think the code is working as it should, but maybe a quick solution would be to convince vtk that the data bounds are much larger that what they really are so that it always renders as internal. Is there a way to do this?

thanks,
carlos



On Mon, May 15, 2017 at 12:18 PM, Aashish Chaudhary [hidden email]> wrote:
Hi Carlos, 

Can you send a picture of the effect you are mentioning? We have a demo that uses VR in OpenVR but we didn't notice the artifact that you have mentioned but we also have not spent as much time as you did. 

- Aashish

On Mon, May 15, 2017 at 11:42 AM Carlos Lopez <[hidden email]> wrote:
Hello,

I'm visualizing a dataset from the visible human project using openVR and I notice that when the camera is outside of the bounds of the dataset, the data renders in a way that the bounding box is noticeable; because of the stereo projection, It is possible to see that the volumetric data is projected onto the faces of the bounding box (this is not visible in 2D, either from a monitor or if I close one eye in the HMD).

If the camera is inside the bounding box, then the data renders in a way that this effect is no longer visible, the projection plane parallel to the current view removes the small discontinuity and the 3D perspective is restored.

Is it possible to configure the volume rendering so that it always behaves as if the camera is inside the dataset?

thanks,
carlos

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Re: Volume visualization with OpenVR

Aashish Chaudhary-2
Thank you so much! We are looking into it as we have few ideas and will post an update soon. 

- Aashish

On Tue, May 16, 2017 at 10:44 AM Carlos Lopez <[hidden email]> wrote:
Hi Aashish,

vtk is 7.1.1 with SHA:
b86da7eef93f75c4a7f524b3644523ae6b651bc4

the exact dataset I'm using is custom, but the issue might be the same with any volumetric imagedata.

best,
carlos



On Mon, May 15, 2017 at 2:48 PM, Aashish Chaudhary <[hidden email]> wrote:
Thanks for the images Carlos. Could you please send us the exact SHA/Version of VTK and also if you can point to the dataset (I know where it is but just in case). 

We have fixed a related view-clipping issue and since then we have not find any issues. It is possible that 1) There is a bug 2) This is related to perception since one eye is inside and the other is outside. 

- Aashish

On Mon, May 15, 2017 at 12:52 PM Carlos Lopez <[hidden email]> wrote:
Hi Aashish,

Here are the screenshots.

In external.png, notice how the arm is being rendered differently for this particular angle; in the HMD I get the sense there is a sharp edge along the arm.

When the camera is close enough, the mode of projection changes, and it looks like internal.png; here I do not see any edges and the 3D effect feels better to me.

In the transition, for very specific points of view, I get the in-between.png picture.

I think the code is working as it should, but maybe a quick solution would be to convince vtk that the data bounds are much larger that what they really are so that it always renders as internal. Is there a way to do this?

thanks,
carlos



On Mon, May 15, 2017 at 12:18 PM, Aashish Chaudhary [hidden email]> wrote:
Hi Carlos, 

Can you send a picture of the effect you are mentioning? We have a demo that uses VR in OpenVR but we didn't notice the artifact that you have mentioned but we also have not spent as much time as you did. 

- Aashish

On Mon, May 15, 2017 at 11:42 AM Carlos Lopez <[hidden email]> wrote:
Hello,

I'm visualizing a dataset from the visible human project using openVR and I notice that when the camera is outside of the bounds of the dataset, the data renders in a way that the bounding box is noticeable; because of the stereo projection, It is possible to see that the volumetric data is projected onto the faces of the bounding box (this is not visible in 2D, either from a monitor or if I close one eye in the HMD).

If the camera is inside the bounding box, then the data renders in a way that this effect is no longer visible, the projection plane parallel to the current view removes the small discontinuity and the 3D perspective is restored.

Is it possible to configure the volume rendering so that it always behaves as if the camera is inside the dataset?

thanks,
carlos

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