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

Sebastian Heerwald bastiheerwald at live.de
Tue Nov 29 10:32:43 EST 2016

Hello VTK team and users,

I've been working with the latest trunk of VTK (7.1 rc2) and wanted to use the OpenVR Framework (with HTC Vive).
This works great except for the volume rendering. Currently there is a view depended
distortion within the volume rendering.
If I look onto the volume rendering and move around it, there appear "refraction" lines.
In front of this line the dataset is rendered correctly, and behind this line too. But onto
that line the dataset gets distorted into another "orientation". So we have one
orientation on the one side of the line and antoher orientation on the other side.
This is bad because the eye cameras look from different positions onto this volume
rendering and because this is view dependend we get non-matching stereo output.

I've tried to track this down and I've seen, that the shader code for the GPURaycaster
is independed from using standard rendering, stereo-anaglyph rendering and VR rendering.
So it seems, that some transformations for this shader aren't set correctly.
But I couldn't figure out which one.

The one thing I could figure out is, that the ray which is used for raycasting, doesn't go
into the right direction. If I assume a bounding box around the dataset which is used for
volume rendering, the refraction lines seem to go along the edges of the bounding box cube.

So I think there is a wrong transformation in this context. But currently I couldn't find
any mistake there.

I've tested everything with different volume data but it was always the same.

My question is:
Did anyone experience these issues? Has someone a fix for that or knows how to find a solution?

Best Regards

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