# For vtkLODProp3D switching,is possible to get the previous LOD ID?

**URL:** https://discourse.vtk.org/t/for-vtklodprop3d-switching-is-possible-to-get-the-previous-lod-id/9182
**Category:** Support
**Created:** [August 21, 2022, 3:10pm UTC](https://discourse.vtk.org/t/for-vtklodprop3d-switching-is-possible-to-get-the-previous-lod-id/9182 "2022-08-21T15:10:37Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![AlexLuya](https://discourse.vtk.org/user_avatar/discourse.vtk.org/alexluya/32/4036_2.png) [@AlexLuya](https://discourse.vtk.org/u/AlexLuya)
#### Post date: [August 21, 2022, 3:10pm UTC](https://discourse.vtk.org/t/for-vtklodprop3d-switching-is-possible-to-get-the-previous-lod-id/9182/1 "2022-08-21T15:10:37Z")

</div>

Hello,there four methods to get LOD ID

```auto
GetLastRenderedLODID
GetSelectedPickLODID
GetSelectedLODID
GetPickLODID

```

But their api docs are quite confusing for me,so I add an observer to render windows to listen ModifiedEvent,which will print all four LOD IDs when switching,and get output like this:

```auto
...
GetLastRenderedLODID: 1000
GetSelectedPickLODID: 1000
GetSelectedLODID: 1000
GetPickLODID: 1000

GetLastRenderedLODID: 1001
GetSelectedPickLODID: 1000
GetSelectedLODID: 1000
GetPickLODID: 1001

GetLastRenderedLODID: 1000
GetSelectedPickLODID: 1000
GetSelectedLODID: 1000
GetPickLODID: 1000

GetLastRenderedLODID: 1002
GetSelectedPickLODID: 1000
GetSelectedLODID: 1000
GetPickLODID: 1002
...

```

Based on these outputs,can I assume that:

```auto
GetLastRenderedLODID/GetPickLODID will return the current LOD ID
GetSelectedPickLODID/GetSelectedLODID will return the previous LOD ID

```

If yes,what is the difference inside pairs?

```auto
GetLastRenderedLODID vs GetPickLODID
GetSelectedPickLODID vs GetSelectedLODID

```