# Hover Points/Cells Implementation

**URL:** https://discourse.paraview.org/t/hover-points-cells-implementation/12853
**Category:** Development
**Created:** [September 13, 2023, 1:31pm UTC](https://discourse.paraview.org/t/hover-points-cells-implementation/12853 "2023-09-13T13:31:33Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Michael\_Jackson](https://discourse.paraview.org/user_avatar/discourse.paraview.org/michael_jackson/32/293_2.png) [@Michael\_Jackson](https://discourse.paraview.org/u/Michael_Jackson)
#### Post date: [September 13, 2023, 1:31pm UTC](https://discourse.paraview.org/t/hover-points-cells-implementation/12853/1 "2023-09-13T13:31:33Z")

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We are writing a VTK based application and would like to implement a points/cells hover capability that gives information about what is hovered. We tried a few different approaches using both vtkHardwarePicker and vtkCellPicker/vtkPointPicker. For the hardware picker unstructured grids work just fine but when hovering over a vtkImagData the Cell Ids that the picker selects is just plain wrong. We tried the vtkCellPicker which gives the correct answer but takes about 10 seconds to get that answer ( in release mode on a fairly recent machine). When we tried out ParaView’s hover cells feature it is very quick to highlight the cell and give a correct answer under all the various types of geometries that we throw at it.

Could any of the ParaView developers give some thoughts on ParaView’s implementation? I tried working through the ParaView code but got as far as the SMProxyRender class then got lost in that implememtation.

Thank you.