# Problem displaying Structured Grid when loading from Programmable Source
**URL:** https://discourse.paraview.org/t/problem-displaying-structured-grid-when-loading-from-programmable-source/3051
**Category:** ParaView Support
**Created:** [November 26, 2019, 3:48pm UTC](https://discourse.paraview.org/t/problem-displaying-structured-grid-when-loading-from-programmable-source/3051 "2019-11-26T15:48:43Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@kenneth-loenbaek](https://discourse.paraview.org/u/kenneth-loenbaek)
#### Post date: [November 26, 2019, 3:48pm UTC](https://discourse.paraview.org/t/problem-displaying-structured-grid-when-loading-from-programmable-source/3051/1 "2019-11-26T15:48:43Z")
Hi,
I am trying to make a file reader for a structured grid file that is not currently supported, but I can read it into a numpy array.
To start simple I tried to make a programmable source which just creates a cube (Output Data Set Type: _vtkStructuredGrid_)
```python
import numpy as np
# Cube
xs = np.linspace(0,1,10)
ys = np.linspace(0,1,10)
zs = np.linspace(0,1,10)
dims = [len(xs),len(ys),len(zs)]
# Setting S-Grid extent
output.SetExtent([0,len(xs)-1,0,len(ys)-1,0,len(zs)-1])
# VTK points
points = vtk.vtkPoints()
points.Allocate(dims[0] * dims[1] * dims[2])
# Adding grid points
for iz, z in enumerate(zs):
for iy, y in enumerate(ys):
for ix, x in enumerate(xs):
fi = iz*len(xs)*len(ys)+iy*len(xs)+ix # Flat index
points.InsertPoint(fi,[x,y,z])
# Adding points to vtkStructuredGrid
output.SetPoints(points)
```
Which does not through any error. From the information tab I find:
* * *
Number of Cells: 729
Number of Points: 1000
* * *
As expected. But I do not get any output in the RenderView.
Does anybody have an idea why?
I tried to create a table with the following script (Output Data Set Type: _vtkTable_):
```python
import numpy as np
# Cube
xs = np.linspace(0,1,10)
ys = np.linspace(0,1,10)
zs = np.linspace(0,1,10)
# Flattining cube in index
out = np.zeros([len(xs)*len(ys)*len(zs),3])
for iz, z in enumerate(zs):
for iy, y in enumerate(ys):
for ix, x in enumerate(xs):
fi = iz*len(xs)*len(ys)+iy*len(xs)+ix # Flat index
out[xis,:] = [x,y,z]
# Adding points to vtkTable
output.RowData.append(out[:,0],"x")
output.RowData.append(out[:,1],"y")
output.RowData.append(out[:,2],"z")
```
It creates the expected table. Then using the _Table to Structured Grid_ filter to make it into a grid. This way works with out any problem.
When comparing the two methods above from the information tab the only difference I find is that the memory usage is different:
* * *
Memory (StructuredGrid): 0.012 MB
Memory (Table): 0.024 MB
* * *
I would love to hear if anybody has an idea for what I am missing?!
---
### Author:  [@jfavre](https://discourse.paraview.org/u/jfavre)
#### Post date: [November 26, 2019, 5:11pm UTC](https://discourse.paraview.org/t/problem-displaying-structured-grid-when-loading-from-programmable-source/3051/2 "2019-11-26T17:11:02Z")
There are two parts you must program. See page 167-168 of the ParaView Guide.
You are missing a script for the RequestInformation part. It basically advertizes what the source can produce. This is where you set the dimensions of your grid.
> executive = self.GetExecutive()
> outInfo = executive.GetOutputInformation(0)
> dims = [10, 10, 10] # x-dims, y-dims, z-dims
> outInfo.Set(executive.WHOLE\_EXTENT(), 0, dims[0]-1 , 0, dims[1]-1 , 0, dims[2]-1)
Then the execution part called “Script” is a modified version of your original test
> import numpy as np
> executive = self.GetExecutive()
> outInfo = executive.GetOutputInformation(0)
> exts = [executive.UPDATE\_EXTENT().Get(outInfo, i) for i in range(6)]
> dims=[exts[1]+1, exts[3]+1, exts[5]+1]
> #Cube
> xs = np.linspace(0,1,dims[0])
> ys = np.linspace(0,1,dims[1])
> zs = np.linspace(0,1,dims[2])
> #Setting S-Grid extent
> output.SetExtent(exts)
> #vtk points
> points = vtk.vtkPoints()
> points.Allocate(dims[0] \* dims[1] \* dims[2])
> #Adding grid points
> for iz, z in enumerate(zs):
> for iy, y in enumerate(ys):
> for ix, x in enumerate(xs):
> fi = iz\*len(xs)_len(ys)+iy_len(xs)+ix # Flat index
> points.InsertPoint(fi,[x,y,z])
> #Adding points to vtkStructuredGrid
> output.SetPoints(points)
---
### Author:  [@kenneth-loenbaek](https://discourse.paraview.org/u/kenneth-loenbaek)
#### Post date: [November 27, 2019, 9:18am UTC](https://discourse.paraview.org/t/problem-displaying-structured-grid-when-loading-from-programmable-source/3051/3 "2019-11-27T09:18:02Z")
Thank you so much Jean. It works right out of the box. (except that for some reason the multiplication (\*) is lost for the flat index (`fi`), it might be that if you make the code cell, a python code cell it would look and copy as expected)
With that said, it seems that this relatively simple example is fairly convoluted and I do not understand why _RequestInformation_ is needed. I did look at chapter 12 in the ParaView Guide. Taking example 12.2.3 _Reading a CSV file with particles_ no _RequestInformation_ is needed and the example seems to be similar.
Is it because it is required by the _vtkStructuredGrid_ to set _WHOLE\_EXTENT_?
Could you point me to any documentation about this?