Hi,
Yes, there are some rounding errors in the matrix libraries that we use
which generate tiny numbers like this. Given that it represents a
translation
of 0.61 nanometres, I normally find that this doesn't make any
difference to
anything - even when concatenated with other transformations with
similar
rounding errors. Do you have an example of where this is actually
important?
All the best,
Mark
On 23 Apr 2010, at 08:38, Junqian Gordon Xu wrote:
> flirt -in $frame$slice -ref $frame"1"$slice -out
> $frame"_xenc"$slice -omat $tempmat -2D
>
> $tempmat:
>
> 0.989301 -0.145891 0 3.07181
> 0.145891 0.9893 0 -5.26495
> 0 0 1 6.10647e-07
> 0 0 0 1
>
> When running a slice by slice flirt -2D registration, the output mat
> sometimes (seems randomly) contains a small z translation (e.g.
> 6.10647e-07, see above). The output $frame"_xenc"$slice is fine
> though.
>
> This z translation causes trouble when one tries to concatenate
> transformations later on. I currently use the following line to
> reset the z-trans value back to 0.
>
> awk 'NR==3 {$4=0}1' $tempmat > $mat
>
> I don't think it's of a high priority to be investigated or fixed,
> but thought it's good to point it out for people going down the same
> route.
>
> Regards
> Gordon
>
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