# Can .vtp files hold multiple data fields or just one?
**URL:** https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245
**Category:** ParaView Support
**Tags:** vtk
**Created:** [November 13, 2023, 6:18pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245 "2023-11-13T18:18:47Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 13, 2023, 6:18pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/1 "2023-11-13T18:18:48Z")
The following Python code converts a `.vtk` file to a `.vtp` file for viewing using e.g. Glance:
```py
# Read VTK
reader = vtkStructuredGridReader()
reader.SetFileName(filename + ".vtk")
# Extract surface
surface_filter = vtkDataSetSurfaceFilter()
surface_filter.SetInputConnection(reader.GetOutputPort())
clean_filter = vtkCleanPolyData()
clean_filter.SetInputConnection(surface_filter.GetOutputPort())
# Save output to a VTP file
writer = vtkXMLPolyDataWriter()
writer.SetFileName(filename + ".vtp")
writer.SetInputConnection(clean_filter.GetOutputPort())
writer.Write()
```
This works fine, but when I have multiple fields, such as `Directivity_dBi` and `Directivity_linear`:
```py
# vtk DataFile Version 3.0
3D Farfield
ASCII
DATASET STRUCTURED_GRID
DIMENSIONS 1 91 181
POINTS 16471 double
-1.000000e+00 1.000000e+00 4.006663e+01
4.257683e-01 1.000000e+00 4.003194e+01
1.847900e+00 1.000000e+00 3.993014e+01
...
-1.000000e+00 1.000000e+00 -1.754531e+01
POINT_DATA 16471
SCALARS Directivity_dBi double 1
LOOKUP_TABLE default
7.775559e+00
7.765758e+00
7.738521e+00
...
-1.634019e+01
-1.635408e+01
-1.633920e+01
SCALARS Directivity_linear double 1
LOOKUP_TABLE default
5.991781e+00
5.978273e+00
5.940897e+00
...
2.322637e-02
2.315217e-02
2.323166e-02
```
…it only seems to write `Directivity_dBi` to the `.vtp` file, ignoring `Directivity_linear` completely. I am able to view `pattern_1_2400000000.0.vtk` and both Directivity entries are there:
* * *
Attached both files for reference (input `.vtk` and output `.vtp`):
- **VTK:** [pattern\_1\_2400000000.0.vtk](https://discourse.paraview.org/uploads/short-url/pyFb2VaTynEPxozVE94PL9jcmxg.vtk) (1.1 MB)
- **VTP:** [pattern\_1\_2400000000.0.vtp](https://discourse.paraview.org/uploads/short-url/aNzwW8Lmde4cetsbWY4DI9ZDICH.vtp) (687.8 KB)
* * *
Is there anything I could modify to ensure both data fields are passed?
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 14, 2023, 8:55am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/2 "2023-11-14T08:55:48Z")
> Can .vtp files hold multiple data fields or just one?
Of course they can (generated with ParaView directly):
[pattern\_1\_2400000000.0\_kw.vtp](https://discourse.paraview.org/uploads/short-url/b3NZU16GyKf8KKNQe2QpMNe2lOI.vtp) (1.0 MB)
I don’t see anything wrong in your VTK code though. Inspect the outputs of each of your filter to see why the array is disapearing.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 14, 2023, 12:28pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/3 "2023-11-14T12:28:20Z")
> [@mwestphal](#):
>
> I don’t see anything wrong in your VTK code though. Inspect the outputs of each of your filter to see why the array is disapearing.
Printing `surface_filter` doesn’t show much (or at least I’m not sure if there’s anything interesting to extract):
```auto
vtkDataSetSurfaceFilter (0x118645190)
Debug: Off
Modified Time: 136
Reference Count: 2
Registered Events: (none)
Executive: 0x600002168500
ErrorCode: Undefined error: 0
Information: 0x60000393c5a0
AbortExecute: Off
Progress: 0
Progress Text: (None)
PieceInvariant: 0
PassThroughCellIds: Off
PassThroughPointIds: Off
OriginalCellIdsName: vtkOriginalCellIds
OriginalPointIdsName: vtkOriginalPointIds
NonlinearSubdivisionLevel: 1
FastMode: 0
Delegation: 0
```
And removing `clean_filter` doesn’t fix the problem, so that filter is definitely not the issue. Are you able to reproduce this when running the script using the `vtk` module?
Perhaps another question I should ask in advance is this: if I also wish to assign different coordinate points, i.e. this part:
```py
DATASET STRUCTURED_GRID
DIMENSIONS 1 91 181
POINTS 16471 double
-1.000000e+00 1.000000e+00 4.006663e+01
4.257683e-01 1.000000e+00 4.003194e+01
1.847900e+00 1.000000e+00 3.993014e+01
...
```
to the second set of the scalar data, can VTP support this? That’s my ultimate goal, so that the coordinates also change when the scalar values are different.
Another alternative would be to produce 2 `.vtk` files (which I can handle easily), but I’m not sure how we could merge them into a single `.vtp`.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 14, 2023, 2:17pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/4 "2023-11-14T14:17:05Z")
> [@WarinSpace\_Game](#):
>
> Printing `surface_filter` doesn’t show much
Print the _output_ of the filter instead 🙂
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 14, 2023, 3:12pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/5 "2023-11-14T15:12:22Z")
`surface_filter.GetOutput()` returns:
```py
vtkPolyData (0x13868c3e0)
Debug: Off
Modified Time: 357
Reference Count: 2
Registered Events: (none)
Information: 0x60000133b300
Data Released: False
Global Release Data: Off
UpdateTime: 0
Field Data:
Debug: Off
Modified Time: 354
Reference Count: 1
Registered Events: (none)
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Number Of Points: 0
Number Of Cells: 0
Cell Data:
Debug: Off
Modified Time: 357
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x60000397f990)
Event: 33
EventName: ModifiedEvent
Command: 0x6000014703c0
Priority: 0
Tag: 1
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Point Data:
Debug: Off
Modified Time: 356
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x60000397f960)
Event: 33
EventName: ModifiedEvent
Command: 0x6000014703c0
Priority: 0
Tag: 1
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Bounds:
Xmin,Xmax: (1, -1)
Ymin,Ymax: (1, -1)
Zmin,Zmax: (1, -1)
Compute Time: 0
Editable: false
Number Of Points: 0
Point Coordinates: 0x0
PointLocator: 0x0
CellLocator: 0x0
Number Of Vertices: 0
Number Of Lines: 0
Number Of Polygons: 0
Number Of Triangle Strips: 0
Number Of Pieces: 1
Piece: -1
Ghost Level: 0
CellsBounds:
Xmin,Xmax: (1, -1)
Ymin,Ymax: (1, -1)
Zmin,Zmax: (1, -1)
CellsBounds Time: 0
```
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 14, 2023, 4:18pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/6 "2023-11-14T16:18:29Z")
> [@WarinSpace\_Game](#):
>
> ```auto
> Number Of Points: 0
> Number Of Cells: 0
>
> ```
After updating the filter.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 14, 2023, 11:01pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/7 "2023-11-14T23:01:34Z")
After `surface_filter.Update()`:
```py
vtkPolyData (0x1116476f0)
Debug: Off
Modified Time: 560
Reference Count: 2
Registered Events: (none)
Information: 0x600000d4fe40
Data Released: False
Global Release Data: Off
UpdateTime: 561
Field Data:
Debug: Off
Modified Time: 513
Reference Count: 1
Registered Events: (none)
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Number Of Points: 16471
Number Of Cells: 16200
Cell Data:
Debug: Off
Modified Time: 560
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x60000270f900)
Event: 33
EventName: ModifiedEvent
Command: 0x600000a086e0
Priority: 0
Tag: 1
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Copy Tuple Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 1 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Point Data:
Debug: Off
Modified Time: 558
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x60000270f8d0)
Event: 33
EventName: ModifiedEvent
Command: 0x600000a086e0
Priority: 0
Tag: 1
Number Of Arrays: 1
Array 0 name = Directivity_dBi
Number Of Components: 1
Number Of Tuples: 16471
Copy Tuple Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 1 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars:
Debug: Off
Modified Time: 555
Reference Count: 1
Registered Events: (none)
Name: Directivity_dBi
Data type: double
Size: 16471
MaxId: 16470
NumberOfComponents: 1
Information: 0x0
Name: Directivity_dBi
Number Of Components: 1
Number Of Tuples: 16471
Size: 16471
MaxId: 16470
LookupTable: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Bounds:
Xmin,Xmax: (-31.173, 29.0485)
Ymin,Ymax: (-29.3445, 31.424)
Zmin,Zmax: (-19.2903, 40.0666)
Compute Time: 574
Editable: false
Number Of Points: 16471
Point Coordinates: 0x600001b0b600
PointLocator: 0x0
CellLocator: 0x0
Number Of Vertices: 0
Number Of Lines: 0
Number Of Polygons: 16200
Number Of Triangle Strips: 0
Number Of Pieces: 1
Piece: 0
Ghost Level: 0
CellsBounds:
Xmin,Xmax: (-31.173, 29.0485)
Ymin,Ymax: (-29.3445, 31.424)
Zmin,Zmax: (-19.2903, 40.0666)
CellsBounds Time: 575
```
Looks like only `Directivity_dBi` is written and `Directivity_linear` is ignored.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 15, 2023, 8:19am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/8 "2023-11-15T08:19:47Z")
> [@WarinSpace\_Game](#):
>
> `Number Of Arrays: 1`
Then check the output of the reader itself.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 15, 2023, 8:28am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/9 "2023-11-15T08:28:15Z")
`reader.Update()` and then `reader.GetOutput()` returns:
```py
vtkStructuredGrid (0x110fa1bc0)
Debug: Off
Modified Time: 380
Reference Count: 2
Registered Events: (none)
Information: 0x6000003707e0
Data Released: False
Global Release Data: Off
UpdateTime: 385
Field Data:
Debug: Off
Modified Time: 350
Reference Count: 1
Registered Events: (none)
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Number Of Points: 16471
Number Of Cells: 16200
Cell Data:
Debug: Off
Modified Time: 358
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x600002930fc0)
Event: 33
EventName: ModifiedEvent
Command: 0x600000424690
Priority: 0
Tag: 1
Number Of Arrays: 0
Number Of Components: 0
Number Of Tuples: 0
Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Point Data:
Debug: Off
Modified Time: 380
Reference Count: 1
Registered Events:
Registered Observers:
vtkObserver (0x600002930f90)
Event: 33
EventName: ModifiedEvent
Command: 0x600000424690
Priority: 0
Tag: 1
Number Of Arrays: 1
Array 0 name = Directivity_dBi
Number Of Components: 1
Number Of Tuples: 16471
Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
Scalars:
Debug: Off
Modified Time: 377
Reference Count: 1
Registered Events: (none)
Name: Directivity_dBi
Data type: double
Size: 16472
MaxId: 16470
NumberOfComponents: 1
Information: 0x0
Name: Directivity_dBi
Number Of Components: 1
Number Of Tuples: 16471
Size: 16472
MaxId: 16470
LookupTable: (none)
Vectors: (none)
Normals: (none)
TCoords: (none)
Tensors: (none)
GlobalIds: (none)
PedigreeIds: (none)
EdgeFlag: (none)
Tangents: (none)
RationalWeights: (none)
HigherOrderDegrees: (none)
Bounds:
Xmin,Xmax: (-31.173, 29.0485)
Ymin,Ymax: (-29.3445, 31.424)
Zmin,Zmax: (-19.2903, 40.0666)
Compute Time: 399
Editable: false
Number Of Points: 16471
Point Coordinates: 0x600001528510
PointLocator: 0x0
CellLocator: 0x0
Dimensions: (1, 91, 181)
Extent: 0, 0, 0, 90, 0, 180
)
```
So it seems that the problem is in the reading itself rather than the filters.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 15, 2023, 8:31am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/10 "2023-11-15T08:31:17Z")
> [@WarinSpace\_Game](#):
>
> `Number Of Arrays: 1`
Looks like the reader is providing only a single array. Try calling `ReadAllScalarsOn()` and `ReadAllSVectorsOn()` before updating.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 15, 2023, 8:34am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/11 "2023-11-15T08:34:05Z")
Yes! That finally fixed it, thanks a lot!
That helps. Do we also know whether different points can be used for the second array?
> [@WarinSpace\_Game](#):
>
> Perhaps another question I should ask in advance is this: if I also wish to assign different coordinate points, i.e. this part:
>
> ```py
> DATASET STRUCTURED_GRID
> DIMENSIONS 1 91 181
> POINTS 16471 double
> -1.000000e+00 1.000000e+00 4.006663e+01
> 4.257683e-01 1.000000e+00 4.003194e+01
> 1.847900e+00 1.000000e+00 3.993014e+01
> ...
>
> ```
>
> to the second set of the scalar data, can VTP support this? That’s my ultimate goal, so that the coordinates also change when the scalar values are different.
>
> Another alternative would be to produce 2 `.vtk` files (which I can handle easily), but I’m not sure how we could merge them into a single `.vtp`.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 15, 2023, 8:38am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/12 "2023-11-15T08:38:57Z")
> That helps. Do we also know whether different points can be used for the second array?
You should either use another .vtp enterely or store the secondary points as a 3-component point data and switch the points using a dedicated filter (can be done with a calculator).
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 15, 2023, 9:27am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/13 "2023-11-15T09:27:12Z")
Is there any way this could be done in Glance? My goal is to easily toggle between the two by simply changing the selection from the dropdown:
which obviously changes the color, but not the coordinates of the points.
I could obviously export 2 separate .vtp files, but I’d prefer to toggle between the two using a dropdown instead of displaying it as if it is a completely different set of data.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 15, 2023, 9:31am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/14 "2023-11-15T09:31:52Z")
I’m quite sure this cannot be done in glance out of the box.
---
### Author:  [@jourdain](https://discourse.paraview.org/u/jourdain)
#### Post date: [November 16, 2023, 3:13am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/15 "2023-11-16T03:13:03Z")
If you use time as a fake dimension, you can export your data and view it in glance so you can switch between 1 mesh and another but the format will have to be the “web export (.vtkjs)” from ParaView.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 27, 2023, 6:14am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/16 "2023-11-27T06:14:37Z")
Thank you folks - I ended up using separate VTPs and everything works fine.
* * *
Quick question: what’s the proper way to close off the VTK reader? I seem to be getting some `'ascii' codec can't decode byte 0xe2 in position 9403: ordinal not in range(128)` errors which _only_ come up after my VTK operations, so it seems that some file readers might be interfering and need to be properly closed off:
```py
# This works
with open("some_file.txt", "r") as file:
file_content = file.read()
# Read VTK
reader = vtkStructuredGridReader()
reader.SetFileName(filename + ".vtk")
# Extract surface
surface_filter = vtkDataSetSurfaceFilter()
surface_filter.SetInputConnection(reader.GetOutputPort())
clean_filter = vtkCleanPolyData()
clean_filter.SetInputConnection(surface_filter.GetOutputPort())
# Save output to a VTP file
writer = vtkXMLPolyDataWriter()
writer.SetFileName(filename + ".vtp")
writer.SetInputConnection(clean_filter.GetOutputPort())
writer.Write()
# This fails
with open("some_file.txt", "r") as file:
file_content = file.read()
```
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 27, 2023, 8:25am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/17 "2023-11-27T08:25:35Z")
You can try deleting the writer and the reader, but that looks like a bug to me.
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 27, 2023, 10:23am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/18 "2023-11-27T10:23:41Z")
I tried `del reader, writer` but the issue persists.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 27, 2023, 10:31am UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/19 "2023-11-27T10:31:26Z")
Call the python garbage collector ?
---
### Author:  [@WarinSpace\_Game](https://discourse.paraview.org/u/WarinSpace_Game)
#### Post date: [November 27, 2023, 12:06pm UTC](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245/20 "2023-11-27T12:06:03Z")
Same thing happens after calling `gc.collect()` after the `del`.
[Next page](https://discourse.paraview.org/t/can-vtp-files-hold-multiple-data-fields-or-just-one/13245.md?page=2)