[vtkusers] about removing a spere in the 3D image

Kevin H. Hobbs hobbsk at ohiou.edu
Thu Jun 1 06:21:05 EDT 2006

On Thu, 2006-06-01 at 04:41 -0500, Michael Rice wrote:
> I've had to solve a similar problem recently and am curious about  
> your approach. Given an arbitrary geometric shape, how do you chose  
> the viewpoint used to project the 3d geometry into 2d space? Also,  
> doesn't this only work for orthographic projections?

I don't do this at all. I segment an object in a low resolution 3d
image, then I use the surface polydata of that object to eliminate the
object ( or everything else ) from the full resolution 3d image. There
is no projection. Everything is done in 3d. I only render the polydata
to make sure I selected the correct object, everything else is done
without rendering.

> My problem was to remove a perspective projection of an arbitrary  
> geometry from an image. The best solution I could come up with was to  
> render the geometry into the OpenGL back buffer, grab the zbuffer  
> data to create my own vtkImageData mask, resample the mask image to  
> the size of the input image, and then use vtkImageMask to remove the  
> mask from the input image.
> Do you know of a better approach?
> Thanks.
> Michael

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