[vtkusers] store frame + z-buffer as image

[Glen.Coates at csiro.au]

Hi,

I'm a VTK noob so forgive me if this is a FAQ.  I'm writing an application 
that visualises volumetric data by rendering an MIP of the data and 
orthogonal slices through the data in the same renderer.

I'd like to be able to slide the slices through the volume while the MIP
is visible as quickly as possible, however, at present the MIP algorithm
is re-run every time I move one of the slices.

The sensible approach to this problem would be to run the MIP once, store 
the resulting image (and Z-depths for each pixel) somewhere, and then when 
I want to interact by moving the slices, I simply used the cached MIP to 
re-render the scene, using pixels from the slice or the MIP depending on 
the stored Z-depths.

I'm not sure about how to go about implementing this.  Could anyone offer 
any helpful hints?

-- 
Cheers,
Glen