what day? On Aug 4, 2014 10:50 AM, "Bradley Lowekamp" <[email protected]> wrote:
> Hello, > > I have created an Google Hangout event, it should be shared with the > ITKBarCamp Google+ group if others are interested in attending. > > Thanks, > Brad > > On Aug 4, 2014, at 9:36 AM, Nick Tustison <[email protected]> wrote: > > > Hi Brad, > > > > Yes, 2 pm EST would work for me any day this week. > > > > Nick > > > >> On Aug 4, 2014, at 6:13 AM, Bradley Lowekamp <[email protected]> > wrote: > >> > >> Nick, > >> > >> Would 2pm EST on day this week for you for a google hang out? > >> > >> Let's plan on review these points I've made along with the notebooks. > I'd think the likely output is going to be some initial requirements for a > new transform optimizer for composite transforms and the v4 framework. > >> > >> Brad > >> > >>> On Aug 1, 2014, at 10:15 AM, Nick Tustison <[email protected]> > wrote: > >>> > >>> Sorry, Brad, but I'm currently in Salt Lake at a funeral. I'd really > like to understand better so, if you're available, I can do it anytime > during the week on another call. > >>> > >>> Sent from Howling Fantods > >>> > >>>> On Aug 1, 2014, at 7:36 AM, Bradley Lowekamp <[email protected]> > wrote: > >>>> > >>>> Nick, > >>>> > >>>> I hope you can make it to today's TCON. I can demo that notebook I > linked too. It should clarify things. > >>>> > >>>> Brad > >>>> > >>>> On Jul 30, 2014, at 1:57 PM, Nicholas Tustison <[email protected]> > wrote: > >>>> > >>>>>> To try to summaries... sorry if have not been clear enough in my > explanations. > >>>>> > >>>>> No, I blame me—I’m consistently distracted by the scenery outside > here in > >>>>> California and it’s definitely affecting my ability to concentrate > on code > >>>>> questions. > >>>>> > >>>>>> INITIAL QUESTION > >>>>>> > >>>>>> How does composite transform and the "Center" parameter interact? > How does this relate to the virtual domain? > >>>>> > >>>>> The composite transform is agnostic with respect to whether or not a > >>>>> transform has a center or any other fixed parameter set. The only > >>>>> distinction we make is typology with respect to linear/deformable. To > >>>>> be clear, we’re not discussing any of the “Centered” transforms: > >>>>> > >>>>> * CenteredAffineTransform > >>>>> * CenteredEuler3DTransform > >>>>> * CenteredEuler2DTransform > >>>>> * CenteredSimilarity2DTransform > >>>>> > >>>>> None of those transforms are used in ANTs but I don’t think > >>>>> their optimization would be an issue in the new ITKv4 registration > >>>>> framework. > >>>>> > >>>>> The virtual domain is simply defined in terms of standard image > >>>>> geometry (origin, spacing, etc.) and is currently set in terms of the > >>>>> fixed image geometry. > >>>>> > >>>>>> MY UNDERSTANDING > >>>>>> > >>>>>> 1) Using a "Center" initialized transform only works correctly for > a single transform and directly with a composite. ( This is with the > current center initializers, a different approach could be done which takes > into consideration the composition ) > >>>>> > >>>>> I don’t see why it would only work correctly for a single transform. > Suppose > >>>>> I optimize a translation transform to get it’s optimal parameters > for a given > >>>>> registration problem. It’s not clear to me why it would be a > problem to follow > >>>>> that with optimizing an Euler3D transform (which we do all the time > in ANTs). > >>>>> Obviously, we have to specify a staring point for the second > transform (which > >>>>> is identity by default) and perhaps it would be better to have a > different > >>>>> starting point but I don’t see why starting with the default > parameters is a > >>>>> problem. > >>>>> > >>>>> If the “Center initialized transform” is one of the transforms > listed above > >>>>> then we don’t use those. If it’s simply the result of using the > >>>>> CenteredTransformInitializer, then we just pull the > itk::TranslationTransform > >>>>> part from the result and push that translation transform into the > composite > >>>>> transform queue. I don’t see why it would be a problem to then > optimize, > >>>>> for example, the Euler3DTransform which just has 3 translation > parameters > >>>>> and 3 angle parameters to optimize where the center is implicitly > defined > >>>>> (unlike the CenteredEuler3DTransform which does have additional > Center > >>>>> parameters). > >>>>> > >>>>>> 2) The virtual domain should be initialized such that the two > images "Center"s are at the origin. This an alternative to using the > "Center" transform parameters, and better works with composite transforms. > >>>>> > >>>>> Yes, that would probably be a better initialization but I don’t know > why it would > >>>>> be a problem for the current framework to optimize with the origin > elsewhere. > >>>>> Right now, each transform within the composite transform queue is > >>>>> optimized starting from its identity parameters but perhaps the > initializer > >>>>> idea that you propose would improve optimization. > >>>>> > >>>>>> I was not aware that 2 was the best practice with the ITKv4 > framework. Do we have any examples/test/documentation to indicate this? > Further more using the current CenterTransformInitalizers to initialize > the virtual domain is not readily apparent[1] how to map the parameters. > >>>>>> PROPOSAL > >>>>>> > >>>>>> Perhaps we need a new Initializer filter to assist with > initializing the virtual domain to initialize this practice? > >>>>>> > >>>>>> Brad > >> > > _______________________________________________ > Powered by www.kitware.com > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > > Kitware offers ITK Training Courses, for more information visit: > http://kitware.com/products/protraining.php > > Please keep messages on-topic and check the ITK FAQ at: > http://www.itk.org/Wiki/ITK_FAQ > > Follow this link to subscribe/unsubscribe: > http://public.kitware.com/mailman/listinfo/insight-developers >
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