[vtkusers] Dynamically Add and Render Points using vtkPolyData

[Andrew]

Hi All, 

This will be my first post, I am new to VTK so I apologize for any Noobie
mistakes. 

Outline: Our project uses a 2D lidar on a Robot to profile areas as it
moves, we are currently using VTK to visualize these point clouds. 

The application needs to be real time as such we receive 10 scans a second
with roughly 360 points per scan. 

What is the best way to add points to PolyData and render it? 

The current method adds these points to the Polydata via: 
//Setup 
lidar_points = gcnew vtkPoints(); 
lidar_points_colors = gcnew vtkUnsignedCharArray(); 
lidar_points_colors->SetName("LidarPointsColors"); 
lidar_points_colors->SetNumberOfComponents(3); 
lidar_points_data->GetPointData()->SetScalars(lidar_points_colors); 
vertices = gcnew vtkCellArray(); 
lidar_points_data->SetPoints(lidar_points); 
lidar_points_data->SetVerts(vertices); 
lidar_points_data->GetPointData()->SetScalars(lidar_points_colors); 
lidar_points_mapper->ImmediateModeRenderingOn();


//Per scan 
for (point p in scan) 
{ 
   vtkPointData^ newPoint = vtkPointData::New(); 
   int Id = lidar_points->InsertNextPoint(new_lidar_point_x,
new_lidar_point_y, new_lidar_point_z); 
   vertices->InsertNextCell(1); 
   vertices->InsertCellPoint(Id); 
} 
lidar_points->Modified(); 
lidar_points_data->Modified(); 
lidar_points_data->Update(); 

lidar_render_window->Render(); 

I have checked and the Insert for each scan takes 3ms regardless of total
point size of PolyData. 
But the Render(); method starts at 4-5ms for an empty set and quickly grows
to 150ms for 1 million points. which already slows down the 10Hz scan rate. 

Interestingly when the scans stop, using the mouse to interact with the
scene gives a very good FPS even when there are 3 Million points 

The system has a GPU and I can verify the render calls do use the GPU, using
the mouse with 3 Million points maxes the GPU (100% utilization). 

While Points are added and rendered both the GPU and CPU of the system are
below 50%, I have tried using threads to Split adding points from the render
event but Vtk really didnt enjoy that :P 

Any Feed back would be very helpful



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