[Insight-users] surface textures?

[Markus Louw]

Hi Luis

I was wondering also, itk v1.2 seems much better than the october release,
what are the plans for itk in the future.  Will it always be opensource?

Markus
----- Original Message -----
From: "Luis Ibanez" <luis.ibanez@kitware.com>
To: "Markus Louw" <mlouw@unizar.es>
Cc: <insight-users@public.kitware.com>
Sent: Thursday, March 13, 2003 7:07 PM
Subject: Re: [Insight-users] surface textures?


>
> Hi Markus,
>
> You certainly can use VTK for generating
> visualizations of your surface+texture models.
>
> You probably will not find much support for
> performing registration in VTK.
>
> ----
>
> Note that the two following problemes:
>
> 1) generating landmark correspondences
> 2) performing registration based on landmarks
>
> are two complementary parallel problems.
>
> If you solve landmark association, then you
> have certainty in landmark correspondences
> and Registration becomes the trivial problem
> of interpolating a deformation field.
>
> or
>
> If you solve the registration problem, then
> you have a spatial transform (which can
> for example be expressed as a deformation
> field), and with it, the problem of landmark
> correspondance becomes the trivial task of
> mapping one set of landmarks trhough the
> transform.
>
> ---
>
> You don't need Volumetric registration.
> Your problem can be nicely represented in
> ITK using the Mesh and associating RGBPixel
> values to each node.
>
> You will find a description on the use of
> the ITK Mesh in the SoftwareGuide.pdf
> http://www.itk.org/ItkSoftwareGuide.pdf
> Section 4.2 PointSet, pdf-pages 57-67
> Section 4.3 Mesh,     pdf-pages 67-87
>
>
> ---
>
> How dense are the points in the geometry
> of the facial models ? hundreds of points ?
> thousands ?
>
> Are you assuming that the mapping of the
> JPEG 2D texture image to the facial geometry
> is done with certainty ?
>
> This means that the color values associated
> with every node of the geometry will never
> change.
>
> In this case, your registratoin problem
> becomes the challenge of displacing the 3D
> positions of the mesh points in order to get
> closer to the equivalent colors of the other
> textured mesh.
>
> You could implement this in ITK by reusing
> the following components:
>
> 1) Optimizers: GradientDescent, OnePlusOneEvolutionary
> 2) Transforms: Affine, ThinPlateSplines,
>                 VolumeSpines, ElasticBodySpline,
>                 BSpline.
> 3) Interpolator: linear, nearest neighbor
>
>
> and writing on your own the following
> components:
>
> 4) MeshToMesh Metric
> 5) MeshToMesh registration method
>
>
> The registration method in (5) is just a holder
> that will put all the component together and
> then delegates control to the optimizer.
>
> The Metric (4) is where the fun starts. You
> have to figure out a measure that will tell
> how well facial model (color included) matches
> the other facial model after the transformation
> has been applied.
>
> You could imaging some sort of color difference
> evaluated on a per point basis and averaged through
> the surface.
>
> ----
>
> You may want to take a look at the ThinPlatesSplines
> application in the InsightApplications directory.
>
> http://www.itk.org/HTML/ThinPlateSplines.htm
>
>
> ----
>
> You could also use the FEM-based approach and
> model the facial models as surfaces made of some
> kind of elastic material. Define forces between
> the two facial models and then let the FEM framework
> compute the displacemets on the models.
>
>
> -----
>
>
>
> Please let us know if you have other questions.
>
>
>    Thanks
>
>
>      Luis
>
>
>
> -------------------------------------
> Markus Louw wrote:
> > Hi Luis,
> > The problem is to generate a facial database for generating facial
> > hypotheses.  To create a database of landmark correspondences, we need
to
> > identify point matches across training sets.  The problem is therefor a
2D
> > parameterizable surface of 3D points, with a JPEG image which contains
> > intensity colour information...
> >
> > Right now the alternative seems to be VTK, do you know anything about
that?
> >
> > Regards
> > Markus Louw,
> > PhD student, University of Zaragoza, Spain
>
>