[Insight-users] Question about workings of ExponentialDeformationFieldImageFilter

[Anja Ende]

Hello,

Just to confirm:

Id+w = (Id + u) o (Id + v)

should be Id + u + v + u o v

So, w = u + v + u o v

So, there is an additional 'u' that seems to be missing or the more
plausible explanation is there is something that I have not
understood!

Thanks,

Anja


On 20 May 2011 08:04, Anja Ende <anja.ende at googlemail.com> wrote:
>> This addition is need to compute the composition. Let u, v and w be
>> displacement fields, we want w such that
>>  Id+w = (Id + u) o (Id + v)
>>          = Id + v + u_warped_by_v
>>
>> meaning
>>  w = v + u_warped_by_v
>
> Thanks for this Tom. How is this coming about though?
>
> By distributive law, we have:
>
> (Id+u)o(Id+v) = (Id+u)o(Id) + (Id+u)o(v)
>
> I am guessing the second bit generates the u_warped_by_v bit. How does
> (Id+u)o(Id) results in Id.
>
> Thanks,
>
> Anja
>



-- 
Cheers,

Anja