[vtkusers] Polygon triangulation using vtkPolugon::Triangulate

[Frederic DANESI]

Hi Polys,

You are working directly on a vtkCell. Actually, you may have to consider
working on PolyData, which enclosed all your geometric information (points,
cells, 
)
For your example, you can try this (it works ;-))

vtkPoints *polygonPoints  = vtkPoints::New();
vtkPolygon *polygon = vtkPolygon::New();
 
polygonPoints ->SetNumberOfPoints(4); //do not allocate 8 points if you only
fill 4 in 

polygonPoints->InsertPoint(0, 0, 0, 0);
polygonPoints->InsertPoint(1, 1, 0, 0);
polygonPoints->InsertPoint(2, 1, 1, 0);
polygonPoints->InsertPoint(3, 0, 1, 0);
 
polygon->GetPointIds()->SetNumberOfIds(4);
polygon->GetPointIds()->SetId(0, 0);
polygon->GetPointIds()->SetId(1, 1);
polygon->GetPointIds()->SetId(2, 2);
polygon->GetPointIds()->SetId(3, 3);

vtkPolyData *pd = vtkPolyData::New();
pd->Allocate();
pd->InsertNextCell(polygon->GetCellType(),polygon->GetPointIds());
pd->SetPoints(polygonPoints);

vtkTriangleFilter *tri= vtkTriangleFilter::New();
tri->SetInput(pd); //The output of the triangle filter will be a
triangulation of the inputPolyData 

vtkPolyDataMapper *map = vtkPolyDataMapper::New();
map->SetInput(tri->GetOutput());
vtkActor *act = vtkActor::New();
act->SetMapper(map);

You may have to consider buying the VTK books or to have a look to the
examples of the book, such as ClipCow, which will show you how to
reconstruct a polygon from lines and then triangulate it 


Fred.



Cordialement,
F.Danesi
--
Département DINCCS (Département Ingénierie Numérique, Conception
Collaborative et Simulation) 
MICADO / DINCCS 
Pole de Haute Technologie, 7 boulevard Jean Delautre (IFTS) 
08000 Charleville-Mézières 
Tel. : 03.24.41.69.55 / 06.62.76.13.32 
Email : frederic.danesi at dinccs.com 
Web: www.afmicado.com / www.dinccs.com



De : vtkusers-bounces+frederic.danesi=dinccs.com at vtk.org
[mailto:vtkusers-bounces+frederic.danesi=dinccs.com at vtk.org] De la part de
polys_poly at hotmail.com
Envoyé : samedi 23 février 2008 14:26
À : VTK users group
Objet : [vtkusers] Polygon triangulation using vtkPolugon::Triangulate

I am trying to triangulate a polygon.
 
My code is this:
 
polygonPoints  = vtkPoints::New();
polygon = vtkPolygon::New();
 
polygonPoints ->SetNumberOfPoints(8);
polygon->GetPointIds()->SetNumberOfIds(8);
 
polygonPoints->InsertPoint(0, 0, 0, 0);
polygonPoints->InsertPoint(1, 1, 0, 0);
polygonPoints->InsertPoint(2, 1, 1, 0);
polygonPoints->InsertPoint(3, 0, 1, 0);
 
polygon->GetPointIds()->SetId(0, 0);
polygon->GetPointIds()->SetId(1, 1);
polygon->GetPointIds()->SetId(2, 2);
polygon->GetPointIds()->SetId(3, 3);
 
I found out that vtkPolygon has a function named Triangulate 
 
int vtkPolygon::Triangulate (int index,vtkIdList* ptIds, vtkPoints* pts)
 
I tried this:
 
polygon->Triangulate(1, polygon->PointIds, polygonPoints);
 
and get exception error.
 
What do i do wrong?
 
Thanks in advance,
Polys