[vtkusers] ray casting, segmentation

[Andinet Enquobahrie]

Lyubomir Zagorchev wrote:

>I use volume rendering to clip a volume in an arbitrary fashion using image stencil.
>It works great, but after clipping I would like to keep only the visible structures that are displayed on the screen. I understand that volume rendering creates a 2D projection from the 3D volume using color and opacity lookup. Is there any way I can apply that same lookup to the original data voxels so that I can *segment* out the structures of interest in the volume? 
>
>Thanks,
>Lyubomir
>
>  
>
Hi Lyubmor,

If the area that you are clipping out can be approximated by a 
rectangle. In other words, if your "structure of interest" can be 
approximated by a rectangle,
you can do the following....

1) Use vtkInteractorStyleRubberBandPick to draw a rectangle on the 
render window..
2) Use vtkAreaPicker to pick props behind the rectangle you have drawn. 
VtkAreaPicker returns the selected frustum as vtkPlanes.
3) Pass the selected frustum (vtkPlanes) to vtkFrustumExtractor.
4) VtkFrustumExtractor returns the portion of the input dataset that 
lies within a selection frustum i.e your structure of interest

-Andinet



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