[vtkusers] Must reduce cell count !

Sebastien Auclair sxa at fluent.com
Fri Apr 18 15:33:46 EDT 2003

This is a request for some help related to the filtering\reduction of
unnecessary cells in polydata objects.

We must find a way to reduce the amount of cell (polygons\triangles)
displayed by our application.

The common usage of our application is to display extruded models of
non-convex polygons.
Once the extrusion is done and the full model is displayed, it is composed
of at least "10 000 000" triangle cells.
Many of these cells are unnecessary. These unnecessary cells belong to two
cases :

    A) The case related to the previous mails posted in this mailing-list.
"Removing internal cells".
            When extruding a triangulated polygon, the interior edges
produce interior facets.

    B) Facets generated by extrusion are triangulated.
            If you extrude a triangle, (on its normal), you'd get a wedge
with 3 walls and a cap.
            These 3 walls instead of being 3 square are in fact 6 triangle

Let's say we start the process from a square polygon shape. (4 points)
We first tessellate to make sure it will be convex.
We then extrude on the polygon's normal vector.
The end-result is a cube made of "16" cells !!!!! (Way too much !)
Our goal is to get a cube made of 8 cells. (Or 6 would be even better)

How could we reduce the number of cells ?

Thanks for any help !

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