[MINC-users] xfmconcat

[Andrew Janke]

Hi Aaryani,

>  I would like to know what operation does xfmconcat does when I use xfmconcat for two xfm files (i.e., what operation it performs on the trasnformation matrices). I tried looking into the code, but couldn't figure out. If anyone knows please tell me what operation it does on the transformation matrices.

The operation for two successive transformation matricies is a simple
matrix product.

   http://en.wikipedia.org/wiki/Transformation_matrix#Composing_and_inverting_transformations

That said if xfmconcat can't combine two transformations the
transformation will simply be listed in order in the .xfm file. This
typically happens if the transforms being combined aren't all affine
or already a combination of transform types. A good example of this is
an output nonlinear transformation from minctracc. In this case the
transformation is a combination of a linear affine transformation
followed by a grid transform that is expressed in another MINC volume.


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