# How to define different unstructured grids that share the same points (also for different time steps)

**URL:** https://discourse.vtk.org/t/how-to-define-different-unstructured-grids-that-share-the-same-points-also-for-different-time-steps/8041
**Category:** Support
**Created:** [March 12, 2022, 4:02pm UTC](https://discourse.vtk.org/t/how-to-define-different-unstructured-grids-that-share-the-same-points-also-for-different-time-steps/8041 "2022-03-12T16:02:43Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![bva99](https://discourse.vtk.org/user_avatar/discourse.vtk.org/bva99/32/3745_2.png) [@bva99](https://discourse.vtk.org/u/bva99)
#### Post date: [March 12, 2022, 4:02pm UTC](https://discourse.vtk.org/t/how-to-define-different-unstructured-grids-that-share-the-same-points-also-for-different-time-steps/8041/1 "2022-03-12T16:02:44Z")

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Is it possible to define different unstructured grids that share the same Points, without having to write the points in each file? This is supposing only one time-step.

I imagine that vtkMultiPieceDataSet should do so, but I don’t know how to write that in an XML file. A vtkMultiBlockDataSet groups together the unstructured grids, but the Points are always repeated, wasting space.

Furthermore, if the points are the same during different time-steps, can all of the unstructured grids of each time-step reference the same Points?