vtkCellPicker very slow

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1

Hi,

I am implementing some point picking on a mesh with 127000 triangles. I’d love to pick points on the mesh while the user is interacting, but picking can take up to 300ms.
I tried with a mesh of similar size in three.js and there picking only takes 30ms.

Is there something I do wrong in the code? How can I improve performance?

   function cellPickOnActors(renderer, actorsToPickOn, point) {
           // Caching the picker has no performance gain
           // Ephemeral, short lived, picker
           let pointPicker = pointPicker = vtkCellPicker.newInstance(); // Alternative: vtkPointPicker
           pointPicker.setPickFromList(1);
           pointPicker.initializePickList();
           pointPicker.setTolerance(0) // https://discourse.vtk.org/t/cellpicker-example-glitch/1852
           console.assert(Array.isArray(actorsToPickOn))
           actorsToPickOn.forEach(actor => {
               pointPicker.addPickList(actor);
           });
           pointPicker.pick(point, renderer);
           return pointPicker;
       }

Warm greetings,
Emile Sonneveld

2

The vtkCellPicker has a method called AddLocator() for providing a vtkCellLocator that can accelerate the search.

The basic usage is:

  • create a vtkCellLocator
  • use SetDataSet() to put your data into the locator
  • call Update() on the locator
  • add the locator to the picker
3

We don’t have a cellLocator in vtk.js. We do have a hardware selector that allow point picking but not yet cell picking (if I recall correctly). And that one is fast as it is using the pixel of the rendering which is probably what three.js is doing.

4

vtkCellPicker is indeed relatively slow but there are many other pickers in VTK. Hardware-accelerated pickers can be magnitudes faster but they have other limitations (they rely on z buffer, so transparency may cause problems).

5

Thanks for the replys. It seems that in VTK.js, the locators are not implemented yet.

The hardware point picker sounds interesting, but I can’t find it in VTK.js. Anyone knows how to use it?

6

Here are some of its usage throughout the code:

HTH