[vtkusers] How to generate X-Ray Projection

[Lisa Avila]

Hello,


>1. I want to generate X-Ray 2D image from the 3D volume. Some articles on 
>the internet mention that MIP projection can produce image look likes 
>X-Ray image, and some articles mention about "average intensity 
>projection" should be used to obtain X-Ray image. Which one (or both) was 
>wrong?

A MIP projection is a "maximum intensity projection" - the maximum value 
encountered along the ray (either raw scalar or opacity mapping) is used 
for resulting pixel value in the image. Therefore it is not like an x-ray 
in which (usually) the whole volume contributes to the final image. Average 
would be closer to an x-ray but remember this is just a rough 
approximation. You could also write a ray cast function that models x-ray 
attenuation (absorption and scattering) but keep in mind that the ray cast 
mapper only cast primary rays so you couldn't account for any second-order 
scattering effecfts.

Lisa
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