[vtkusers] Bug or Design: Rendering concave polygons with vtkActor2D

[Xiaofeng Z]

Concave polygons are not rendered as expected with vtkPolyDataMapper and vtkActor2D (see below).  Is it by design or is it a bug?  If it's by design, is there any flag can be set to alter the rendering behaviour?

 

Thanks!

Xiaofeng



Hi all,
 
How do I make uniform transparency in a concave polygon, instead of getting multiple shades, e.g. in the attached graph?
 
The polygon are created with:
 
vtkPoints* points = vtkPoints::New();
vtkCellArray* cells = vtkCellArray::New();
points->SetNumberOfPoints(4);
 
// create a concave polygon (equilateral with a cutout at the bottom) 


points->SetPoint(0, 10.0, 10.0, 0.0);
points->SetPoint(1, 110.0, 183.2, 0.0);
points->SetPoint(2, 210.0, 10.0, 0.0);
points->SetPoint(3, 110.0, 110.0, 0.0);
cells->Allocate(1, 5);
cells->InsertNextCell(5);
cells->InsertCellPoint(0);
cells->InsertCellPoint(1);
cells->InsertCellPoint(2);
cells->InsertCellPoint(3);
cells->InsertCellPoint(0);
vtkPolyData* poly = vtkPolyData::New();
poly->Initialize();
poly->SetGlobalWarningDisplay(1);
poly->SetPoints(points);
poly->SetPolys(cells);
 
A vtkActor2D and a vtkPolyDataMapper2D was used for the rendering.

Many thanks!
Xiaofeng





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