[vtkusers] unstructured grid + tetrahedrons

[Bryn Lloyd]

David,

As Jerome says vtkPolyData is for 0D, 1D, 2D cells. But nevertheless 
these cells are in 3D, i.e. triangles in 3D space with coordinates x,y,z.

vtkPolyData cannot hold proper 3D cells (vtkCell3D), such as tetrahedra. 
3D meaning that the cell has a volume.

volume(triangle) = 0.

-Bryn




David Doria wrote:
> On Fri, Dec 11, 2009 at 4:45 AM, Jérôme <jerome.velut at gmail.com> wrote:
>> You are right, polydata is intended to describe 0D (vertices), 1D (lines)
>> and 2D (polygons) cell. Tetrahedrons are the "simplest" 3D cells, such as
>> triangles are the "simplest" 2D cells, but vtkPolyData cannot have 3D cells.
>> However, a tetrahedron is composed of 4 vertices, 6 edges (lines) and 4
>> triangles (polygons) that you can *represents* thanks to a vtkPolyData. when
>> you render a tetrahedral mesh through a polydata, you don't "see" the
>> tetrahedrons, but their bounds.
>>
>>
>> Jerome
> 
> Jerome -
> 
> I'm not sure that is accurate - I believe the whole point of a
> polydata is that it is the most flexible data type in that it is the
> only one that DOES allow 3D cells. I'd have to double check the VTK
> book on that, but maybe someone else can verify this? I've been
> planing to add a brief description of each of these types to the wiki
> for a while so you may have motivated me to get around to it :)
> 
> Thanks,
> 
> David
> _______________________________________________
> Powered by www.kitware.com
> 
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
> 
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
> 
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
> 


-- 
-------------------------------------------------
Bryn Lloyd
Computer Vision Laboratory
ETH Zürich, Sternwartstrasse 7, ETF C110
CH - 8092 Zürich, Switzerland
Tel: +41 44 63 26668
Fax: +41 44 63 21199
-------------------------------------------------