# View disappears and creates artifacts in multiblock pan and rotate
**URL:** https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837
**Category:** ParaView Support
**Created:** [March 17, 2020, 8:20pm UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837 "2020-03-17T20:20:13Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@luigiraffaele](https://discourse.paraview.org/u/luigiraffaele)
#### Post date: [March 17, 2020, 8:20pm UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/1 "2020-03-17T20:20:13Z")
Dear all
I have created a multiblock datafile with two DTM (digital terrain model).
If I pan or rotate the view, it disappears and creates artifacts.
This doesn’t happen in the case I have a single DTM file.
[/uploads/default/original/2X/8/80ba47ca791b24d1c455d674535ffb4a3a9633cc.mp4](https://discourse.paraview.org/uploads/default/original/2X/8/80ba47ca791b24d1c455d674535ffb4a3a9633cc.mp4)
this is the multiblock datafile
[mblc.vtm](https://discourse.paraview.org/uploads/short-url/matBhJFmaokyioF3oDx2FzAaVMo.vtm) (241 Bytes)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 18, 2020, 1:01am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/2 "2020-03-18T01:01:36Z")
please share the associated dtm0.vtp and vtm1.vtp
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### Author:  [@luigiraffaele](https://discourse.paraview.org/u/luigiraffaele)
#### Post date: [March 18, 2020, 6:18am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/3 "2020-03-18T06:18:50Z")
[https://1drv.ms/u/s!AgtqczEzv0qMlJlSqPwN65YZkpbS4g?e=ZDnRmf](https://1drv.ms/u/s!AgtqczEzv0qMlJlSqPwN65YZkpbS4g?e=ZDnRmf)
[https://1drv.ms/u/s!AgtqczEzv0qMlJlTahjfPQAdhn0lXQ?e=xlqC9J](https://1drv.ms/u/s!AgtqczEzv0qMlJlTahjfPQAdhn0lXQ?e=xlqC9J)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 18, 2020, 6:54am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/4 "2020-03-18T06:54:33Z")
Your dataset contains NaN points (id 0 to 484) , which completely breaks the Level Of Details filters which is automatically applied when moving the view around.
You can just disable LOD by setting `Edit -> Settings -> RenderView -> LOD Treshold` to a great value.
However, NaN points are not supported in ParaView, and you will likely have many more issues if you do not remove these points, even occasional crashes.
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### Author:  [@luigiraffaele](https://discourse.paraview.org/u/luigiraffaele)
#### Post date: [March 18, 2020, 8:26am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/5 "2020-03-18T08:26:07Z")
Hi Mathieu
Thank’s for your prompt reply.
Unfortunately, in digital terrain models NaN values are very frequent. A possibility is to set Nan value to zero or another value.I am evaluating this solution in my application.
In any case, I’m searching how change LOD Setting, programmatically, since I start the visualization in bash mode (pvpython) and then rotate and pan with the Interact() method inserted in the pvpython script.
Have you any suggestion or links?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 18, 2020, 8:45am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/6 "2020-03-18T08:45:57Z")
NaN values are fine in data arrays, but not in point coordinates.
Where do you render a NaN points ?
But cleaning them up in a `ProgrammableFilter` should be very easy.
We could even add this functionality to the `Clean` filter.
> In any case, I’m searching how change LOD Setting, programmatically, since I start the visualization in bash mode (pvpython) and then rotate and pan with the Interact() method inserted in the pvpython script.
```
settings = servermanager.ProxyManager().GetProxy("settings", "RenderViewSettings")
settings.LODThreshold = 100000
```
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### Author:  [@luigiraffaele](https://discourse.paraview.org/u/luigiraffaele)
#### Post date: [March 18, 2020, 9:40am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/7 "2020-03-18T09:40:03Z")
> [@luigiraffaele](#):
>
> any suggestion or links?
As you know, a DTM is a series of X,Y,Z value, where Z value is the elevation of the terrain @ x,y location.
I use an .asc file.
As example, yiou can wiew NAN values at the end of this file:
[https://1drv.ms/u/s!AgtqczEzv0qMlJlVD5ZxMQRRS4JPZQ?e=6PawUO](https://1drv.ms/u/s!AgtqczEzv0qMlJlVD5ZxMQRRS4JPZQ?e=6PawUO)
When I render a DTM in paraview, I must define:
“PointData Scalars” (in my vtp file = ‘Elevation’, eg the Z value)
“Points” (in my vtp file = ‘Points’ eg the X,Y,Z coordinates)
“Polys” (in my vtp file = ‘Connectivity’ eg sequence index of linkings points)
The grid mesh must join all the points, which coordinates are defined in “Points”. So, I have to insert the X,Y,Z triple for each points. If in some points there is no elevation (i.e. there is a NAN value), how can I define the Z coordinates of these “Points” in the mesh without using NAN value?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 18, 2020, 9:44am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/8 "2020-03-18T09:44:46Z")
You should either remove these points and the cells associated with it, or use 0 instead of NaN.
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### Author:  [@luigiraffaele](https://discourse.paraview.org/u/luigiraffaele)
#### Post date: [March 18, 2020, 9:46am UTC](https://discourse.paraview.org/t/view-disappears-and-creates-artifacts-in-multiblock-pan-and-rotate/3837/9 "2020-03-18T09:46:24Z")
> [@luigiraffaele](#):
>
> e Z coordinates of these “Points” in the mesh without using NAN value?
Ok, Thanks