drawing/picking on volume rendered image

[Vikram Chalana]

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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