Point distribution model: Difference between revisions

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==Background==

ItThe point distribution model concept has been developed by Cootes,<ref>{{citation

|author = T. F. Cootes

|title = Statistical models of appearance for computer vision

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|year = 1995

|author1=D.H. Cooper |author2=T.F. Cootes |author3=C.J. Taylor |author4=J. Graham |issue = 61

}}</ref> and became a standard in [[computer vision]] for the [[statistical shape analysis|statistical study of shape]]<ref>{{citationcite conference

|title = Shape discrimination in the Hippocampus using an MDL Model

|year = 2003

|conference = IMPI

|url = http://www2.wiau.man.ac.uk/caws/Conferences/10/proceedings/8/papers/133/rhhd_ipmi03%2Epdf

|author = Rhodri H. Davies and Carole J. Twining and P. Daniel Allen and Tim F. Cootes and Chris J. Taylor

|access-date = 2007-07-27

|archive-url = https://web.archive.org/web/20081008194350/http://www2.wiau.man.ac.uk/caws/Conferences/10/proceedings/8/papers/133/rhhd_ipmi03%2Epdf

|archive-date = 2008-10-08

|url-status = dead

}}</ref> and for [[image segmentation|segmentation]] of [[medical imaging|medical images]]<ref name=taylor/> where shape priors really help interpretation of noisy and low-contrasted [[pixel]]s/[[voxel]]s. The latter point leads to [[active shape model]]s (ASM) and [[active appearance model]]s (AAM).

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Due to the PCA properties: eigenvectors are mutually [[orthogonal]], form a basis of the training set cloud in the shape space, and cross at the 0 in this space, which represents the mean shape. Also, PCA is a traditional way of fitting a closed ellipsoid to a Gaussian cloud of points (whatever their dimension): this suggests the concept of bounded variation.

The idea behind PDM'sPDMs is that eigenvectors can be linearly combined to create an infinity of new shape instances that will 'look like' the one in the training set. The coefficients are bounded alike the values of the corresponding eigenvalues, so as to ensure the generated 2n/3n-dimensional dot will remain into the hyper-ellipsoidal allowed ___domain—[[allowable shape ___domain]] (ASD).<ref name=taylor/>

==See also==

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|quote=Images, annotations and data reports are placed in the enclosed zip-file.

|author1=Stegmann, M. B. |author2=Gomez, D. D.

|lastauthorampname-list-style=yesamp }} -->

==External links==

* [https://web.archive.org/web/20080509041813/http://www.isbe.man.ac.uk/~bim/Models/index.html Flexible Models for Computer Vision], Tim Cootes, Manchester University.

* [http://www.icaen.uiowa.edu/~dip/LECTURE/Understanding3.html A practical introduction to PDM and ASMs].