Thread Subject: Rendering of a point cloud

Hello,

      I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.

"Cem " <hiittite@gmail.com> wrote in message <gqdbit$ge8$1@fred.mathworks.com>...
> Hello,
>
> I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.

If you don't have too many points (depending on your machine, of course ;) ) you can generate tetrahedra using "delaunay3" on the points of your region, and then represent them using "trisurf".

"Cem " <hiittite@gmail.com> wrote in message <gqdbit$ge8$1@fred.mathworks.com>...
> Hello,
>
> I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.

If the domain is convex, then it is trivially simple.

Build a triangulated surface using convhulln,
then use trisurf to display the facets of the hull
in red.

If it is not convex, then things get more difficult.
One solution is then to use an alpha shape to define
the domain as a tessellation in 3-d. Then form the
boundary surface of the tessellation, i.e., a
non-convex hull. This surface is easy to find, since
it is composed of those traingulated facets that
appear only once in the list of all faces. Now apply
trisurf.

John

"Cem " <hiittite@gmail.com> wrote in message <gqdbit$ge8$1@fred.mathworks.com>...
> Hello,
>
> I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.




http://www.mathworks.com/matlabcentral/fileexchange/22595


http://www.mathworks.com/matlabcentral/fileexchange/22185


http://giaccariluigi.altervista.org/blog/

"Luigi Giaccari" <giaccariluigi@msn.com> wrote in message <gqdhgc$k0h$1@fred.mathworks.com>...
> "Cem " <hiittite@gmail.com> wrote in message <gqdbit$ge8$1@fred.mathworks.com>...
> > Hello,
> >
> > I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.
>
>
>
>
> http://www.mathworks.com/matlabcentral/fileexchange/22595
>
>
> http://www.mathworks.com/matlabcentral/fileexchange/22185
>
>
> http://giaccariluigi.altervista.org/blog/

Luigi,

I would have pointed this person to your tools, but
if the person has a point cloud that contains internal
points, then a CRUST based tool will not find the
surface, as I understand CRUST. Clearly I need to
look more closely at these tools you have provided.
I apologize that I have not had the time to do so.

However, in reading the original post more carefully,
it looks like the points supplied are indeed boundary
points. I thought it was a full point cloud, not just
the boundary points. As such, Luigi's tools will do
very nicely here.

John

Hello Joan,
     I am now working with Luigi. Thank you for introducing my problem to him.

Cem

"John D'Errico" <woodchips@rochester.rr.com> wrote in message <gqdiea$oi1$1@fred.mathworks.com>...
> "Luigi Giaccari" <giaccariluigi@msn.com> wrote in message <gqdhgc$k0h$1@fred.mathworks.com>...
> > "Cem " <hiittite@gmail.com> wrote in message <gqdbit$ge8$1@fred.mathworks.com>...
> > > Hello,
> > >
> > > I have a point cloud in which I do segmentation to find a region and calculate its volume. I want to color this region of interest and render the surface with say red color to differentiate the region of interest. I have the x, y and z arrays for the boundary. So the question is how to render anything within these coordinates as red, everything else grey color as surface, not as colored dots. Thank you.
> >
> >
> >
> >
> > http://www.mathworks.com/matlabcentral/fileexchange/22595
> >
> >
> > http://www.mathworks.com/matlabcentral/fileexchange/22185
> >
> >
> > http://giaccariluigi.altervista.org/blog/
>
> Luigi,
>
> I would have pointed this person to your tools, but
> if the person has a point cloud that contains internal
> points, then a CRUST based tool will not find the
> surface, as I understand CRUST. Clearly I need to
> look more closely at these tools you have provided.
> I apologize that I have not had the time to do so.
>
> However, in reading the original post more carefully,
> it looks like the points supplied are indeed boundary
> points. I thought it was a full point cloud, not just
> the boundary points. As such, Luigi's tools will do
> very nicely here.
>
> John