[vtkusers] Sharing polyline vtkPoints with trangle strip

Martin, Paul paul.martin at dnvgl.com
Sun Aug 14 10:44:27 EDT 2016


I am using multiple vtkTriangleStrips to render tubes with differing cross-section at each end, e.g. an ellipse at one end and a square at the other end. I am overlaying each of the tube's ends with a vtkPolyLine of contrasting colour to allow the user to view just the end cross-sections and hide the triangulated tube surface. I am creating a repeating timer on the interactor to animate the scene.

I have a separate vtkActor for each of the polylines and the triangle strip. Each of the ends of a tube can be translated and oriented differently when the animation is running.

The issue I have is that I can't find a way of specifying multiple vtkPoints arrays (i.e. one for each polyline) as input to the triangle strip, so I am creating a new vtkPoints array for the triangle strip's vtkPolyData and populating it with the vtkPoints arrays for each polyline in turn. This is repeated at each step in the animation, causing a significant performance hotspot when the number of tubes is scaled up:

// Update triangle strip to reflect transformed polylines
// Get points for each end
vtkPoints points = polylineEnd1Actor().GetMapper().GetInput().GetCell(0).GetPoints();
vtkPoints pointsEnd2 = polylineEnd2Actor().GetMapper().GetInput().GetCell(0).GetPoints();

// Create a new vtkPoints for triangle strip
int pointCountEnd2 = pointsEnd2.GetNumberOfPoints();
for (int i = 0; i < pointCountEnd2; ++i)
  // Append transformed pointsEnd2 to points for triangle strip poly data
  points.InsertNextPoint(pointsEnd2.GetPoint(i)[0], pointsEnd2.GetPoint(i)[1], pointsEnd2.GetPoint(i)[2]);


I would like to find a way of mapping polydata/points of the two polylines directly to the triangle strip's polydata/points, such that when the polyline actors are transformed, their new point coordinates are reflected in the triangle strip without having to create a new vtkPoints.

I am using ActiViz.Net with C#.

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