drawing/picking on volume rendered image

[Yves Starreveld]

Hi, Vikram,

This exact issue came up for us not too long ago.

You can use vtkImplicitVolume to extract information about the volume
along a ray that you can define with a picking operation. Simply choose
a threshold and stop along this ray when you reach that threshold.
(essentially you are extracting the surface at this one point) And then
place a 3D cursor there.

As long as you have a reasonable framerate this gives you a pretty good
interaction with your volume data.

Yves

Yves Starreveld
Robarts Research Institute,
London, Ontario, Canada

Vikram Chalana wrote:
> 
> Hello all,
>         I am a new VTK user and I need some help while trying to do the following:
> 
>         I use volume rendering to display an MRI image set containing the brain.
> Now, on the rendered image of the brain, I would like to draw some
> annotations in 3-D. In particular, using the mouse I would like to mark 3-D
> landmarks, such as the sulcii and gyrii on the brain's surface and have them
> appear on the rendered image. How can I use VTK to do this?
> 
>         I tried the vtkCellPicker and it never seems to pick any cell. The
> vtkPointPicker returns some 3-D coordinates, but I do not know how to
> transform these 3-D view coordinates to dataset coordinates. Is this at all
> possible with volume rendering? Should I be using surface rendering instead?
> 
> Thanks much in advance,
> Vikram
> 
> ___________________________________________
> Vikram Chalana, Ph.D.         MathSoft,Inc.
> 1700 Westlake Ave. N       206.283.8802x314
> Seattle, WA 98109         Fax: 206.283.6310
> 
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