[vtkusers] Are point clouds defined as Unstructured Points

[Amy Squillacote]

Hi Cally,

The main difference between vtkPolyData and vtkUnstructuredGrid is 
whether 3D cells (tetrahedra, hexahedra, etc.) may be used. 
vtkUnstructuredGrid supports such cells; vtkPolyData does not. If a 
vtkUnstructuredGrid and a vtkPolyData were storing the same dataset 
(i.e., no 3D cells), I'd expect the memory allocation for each type of 
dataset to be similar.

A description of the VTK file formats is available here: 
http://www.vtk.org/pdf/file-formats.pdf. Chapter 5 of the 4th edition of 
"The Visualization Toolkit" textbook ("Basic Data Representation") 
provides a good description of the various types of vtkDataSets.

- Amy

Cally K wrote:
> Dear Amy
>  
> Thanks for the reply, I would like to clarify some other issues as 
> well as mentioned In the VTK book - The Visualization Toolkit An 
> Object-Oriented Approach To 3D Graphics, Kitware. What is the 
> difference between Polygonal Data and Unstructured grid, in terms of 
> memory allocation. Sorry, its a beginner question, but i kinda need 
> the information, any other help on data formats would be good also.
>
>  
> On 4/14/08, *Amy Squillacote* <ahs at cfdrc.com <mailto:ahs at cfdrc.com>> 
> wrote:
>
>     Hi Cally,
>
>     Are you using vtkPointSource to generate a point cloud? If so, the
>     point cloud generated is a vtkPolyData. If you're creating the
>     point cloud by hand, you could make it either a vtkPolyData or a
>     vtkUnstructuredGrid.
>
>     - Amy
>
>     Cally K wrote:
>
>         Hi gys,
>           Just some theory questions to ask.. I have to write a paper
>         on data formats. I found alot of information from the book
>
>         The Visualization Toolkit An Object-Oriented Approach To 3D
>         Graphics, Kitware.
>
>         However, I would still like to clarify some stuff, does point
>         cloud come under the term unstructured points. Any other
>         papers that I can refer to ..beside the book. I have read the
>         file formats.
>
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>
>     -- 
>     Amy Squillacote                    Phone: (256) 726-4839
>     Computer Scientist                 Fax: (256) 726-4806
>     CFD Research Corporation           Web: http://www.cfdrc.com
>     <http://www.cfdrc.com/>
>     215 Wynn Drive, Suite 501
>     Huntsville, AL  35805
>
>
>

-- 
Amy Squillacote                    Phone: (256) 726-4839
Computer Scientist                 Fax: (256) 726-4806
CFD Research Corporation           Web: http://www.cfdrc.com
215 Wynn Drive, Suite 501
Huntsville, AL  35805