Odd shaped boundary cells

[Will Schroeder]

Hi David-

Tricky business.

Off the top of my head, I'd create an arbitrary convex polyhedral cell (vtkConvexPolyhedron ?). The problem as I see it is coming up with some well-behaved interpolation functions. You could use Sum(1/r2) combination of the cell's points, properly normalized (similar to vtkPolygon).

As far as some of the other methods (e.g., Contour()), the approach I'd take is to first triangulate the convex polyhedron (generate tetrahedra), and then invoke the method over each of the resulting tetrahedra. Triangulating the convex polyhedron isn't that bad...you might start by placing a point in the center of the cell, triangulating each face of the cell, and then connecting the triangles on the faces of the cell to the center point.

This would be a general approach definitely belonging to the public vtk distribution. Let me know if you do it. Good luck.

Will

At 09:23 AM 4/11/00 +0100, David J Brockley wrote:
>Hi
>
>I'm starting work on a visualisation project that involves cell centred
>data on a refined mesh. The mesh is hexahedral with some global cells
>containing multiple refined cells. The data on the mesh is cell centred.
>
>My problem is that some of the cells are cut by n planes that form an
>arbitrary shaped boundary about the mesh. I need to slice the mesh and
>produce flat shaded regions that cut off correctly where these planes
>intersect the cut plane.
>
>I'm looking at:
>
>Deriving from Cell to produce a hexahedral cell modified by a list of
>cut planes, or
>Writing an algorithm to decompose cut cells into a collection of
>hexahedrons and tetrahedrons.
>
>Any opinions, comments, or crys of 'that's really easy' will be welcome
>as I am new to VTK.
>
>David J Brockley

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