# Fastest way to create 3D topography surface (with holes)
**URL:** https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287
**Category:** Development
**Tags:** python
**Created:** [January 7, 2020, 6:54pm UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287 "2020-01-07T18:54:02Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@MBG](https://discourse.paraview.org/u/MBG)
#### Post date: [January 7, 2020, 6:54pm UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287/1 "2020-01-07T18:54:02Z")
In Python plugin I use the code below to create 3D polydata from reqular 2D grid with holes (NoData values) but it’s works too slow. Maybe should I use some other data type or processing instead?
```
# Define points and triangles for mesh
vtk_points = vtkPoints()
vtk_cells = vtkCellArray()
# Build the meshgrid manually
count = 0
# iterate array
for j in range(0,len(ys)-2):
for i in range(0,len(xs)-2):
# check area
if not mask[j,i] or not mask[j+1,i] or not mask[j,i+1] or not mask[j+1,i+1]:
continue
# Triangle 1
vtk_points.InsertNextPoint(xs[i], ys[j], values[j,i])
vtk_points.InsertNextPoint(xs[i], ys[j+1], values[j+1,i])
vtk_points.InsertNextPoint(xs[i+1], ys[j], values[j,i+1])
triangle = vtkTriangle()
triangle.GetPointIds().SetId(0, count)
triangle.GetPointIds().SetId(1, count + 1)
triangle.GetPointIds().SetId(2, count + 2)
vtk_cells.InsertNextCell(triangle)
# Triangle 2
vtk_points.InsertNextPoint(xs[i], ys[j+1], values[j+1,i])
vtk_points.InsertNextPoint(xs[i+1], ys[j+1], values[j+1,i+1])
vtk_points.InsertNextPoint(xs[i+1], ys[j], values[j,i+1])
triangle = vtkTriangle()
triangle.GetPointIds().SetId(0, count + 3)
triangle.GetPointIds().SetId(1, count + 4)
triangle.GetPointIds().SetId(2, count + 5)
vtk_cells.InsertNextCell(triangle)
count += 6
# Create a polydata object
trianglePolyData = vtkPolyData()
# Add the geometry and topology to the polydata
trianglePolyData.SetPoints(vtk_points)
#trianglePolyData.GetPointData().SetScalars(colors)
trianglePolyData.SetPolys(vtk_cells)
```
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [January 10, 2020, 9:16am UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287/2 "2020-01-10T09:16:59Z")
Can you share an input data and the desired output ?
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### Author:  [@MBG](https://discourse.paraview.org/u/MBG)
#### Post date: [January 10, 2020, 1:51pm UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287/3 "2020-01-10T13:51:40Z")
Source datasets:
[Download the global GEBCO\_2019 Grid - in netCDF format (11 Gbytes, 12 Gbytes uncompressed)](https://www.bodc.ac.uk/data/open_download/gebco/GEBCO_15SEC/zip/)
[Admin 0 – Countries - Download without boundary lakes](https://www.naturalearthdata.com/http//www.naturalearthdata.com/download/50m/cultural/ne_50m_admin_0_countries_lakes.zip)
Actual plugin code to generate vtkUnstructuredGrid with Z coordinate for coloring:
>
And to add attribute to it (like to country name for coloring and labeling):
>
This is the output:
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### Author:  [@MBG](https://discourse.paraview.org/u/MBG)
#### Post date: [January 10, 2020, 1:55pm UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287/4 "2020-01-10T13:55:54Z")
For now, I don’t know more optimal way to get produce this visualization. Is it the optimal datatype for the task? We have Z coordinate in the mesh geometries and as the separate attribute - could we exclude it but still have the ability for mesh coloring by Z coordinate? Could we save additional attribute like to country name by more optimal way (for now it’s saved separately for every cell as I see)?
---
### Author:  [@yohanlty\_total](https://discourse.paraview.org/u/yohanlty_total)
#### Post date: [March 4, 2020, 5:16pm UTC](https://discourse.paraview.org/t/fastest-way-to-create-3d-topography-surface-with-holes/3287/5 "2020-03-04T17:16:52Z")
Hi,
I am trying to learn what is efficient and I came across this [https://vtk.org/Wiki/VTK/Tutorials/DataArrays](https://vtk.org/Wiki/VTK/Tutorials/DataArrays)
It mainly deals with the loss of performances related to the generic API.
From what I have read but not tested in the source code, using iterator + a second class to parallelize with multithreading seems the way to go (I am currently looking at _ParaView-v5.7.0/VTK/Imaging/Core/vtkImageBlend.cxx_).
The next thing would be to reduce cache misses on the 2D array **values** by adding a Morton Index ([https://en.wikipedia.org/wiki/Z-order\_curve](https://en.wikipedia.org/wiki/Z-order_curve))
Hopefully this would help.
Best regards