[vtkusers] vtkVolumeProperty IndependentComponents On and Off

[Kenji Tsumura]

Hi Aashish,

Thank you.
I tried with vtkGPUVolumeRayCastMapper.
An error occurs without setting IndependentComponentsOff.
It seems  the error occurs in vtkOpenGLGPUVolumeRayCastMapper::BuildShader (See the attached file).

Kenji

From: Aashish Chaudhary [mailto:aashish.chaudhary at kitware.com]
Sent: Monday, December 07, 2015 1:54 PM
To: Kenji Tsumura
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] vtkVolumeProperty IndependentComponents On and Off



On Mon, Dec 7, 2015 at 12:19 PM, Kenji Tsumura <kenji.tsumura at neosoftmedical.com<mailto:kenji.tsumura at neosoftmedical.com>> wrote:
Hello,

I have 3D cardiac MRI data (magnitude data and velocity data), and would like to display the volume rendering of the two data.
I create vtkVolume with two components  (first one is velocity data and second one is magnitude data) and use vtkSmartVolumeMapper.
When I set IndependentComponentsOn to the volume property, I can see what I want (refer to the first figure).
But this setting disables GPU rendering and it is slow.

I don't remember vtkSmartVolumeMapper has this logic, I will have a look. In the old GPU raycast mapper, there was some issue with independent components so may be that is the reason that smart volume mapper switched to fixed point ray cast.

Is there a particular reason you are using vtkSmartVolumeMapper?  You can directly use GPUVolume RayCastMapper

My understanding is that I have to use IndependentComponentsOff to make the mapper use GPU rendering.
When I set IndependentComponentsOff, only one color transfer function, and only one scalar opacity function to the volume property,
the magnitude data (the second component) is also color-coded (refer to the second figure).
I thought this contradicts the method comments of IndependentComponentsOn/ IndependentComponentsOff.

“For 2 component data, the first is passed through the first color transfer function and the second component is passed through the first opacity transfer function.”

Am I missing something?
Can I make the volume rendering look the same as using two components?

Thank you,

BTY, I use v6.3.0, OpenGL2.

--
Kenji Tsumura

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--
| Aashish Chaudhary
| Technical Leader
| Kitware Inc.
| http://www.kitware.com/company/team/chaudhary.html
Disclaimer: The information contained in this communication may be confidential, is intended only for the use of the recipient(s) named above, and may be legally privileged. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication, or any of its contents, is strictly prohibited. If you have received this communication in error, please return it to the sender immediately and delete the original message and any copy of it from your computer system. If you have any questions concerning this message, please contact the sender.
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