# How do I construct a surface bordered by two perimeters?

**URL:** https://discourse.vtk.org/t/how-do-i-construct-a-surface-bordered-by-two-perimeters/13758
**Category:** Support
**Tags:** python
**Created:** [April 20, 2024, 1:32pm UTC](https://discourse.vtk.org/t/how-do-i-construct-a-surface-bordered-by-two-perimeters/13758 "2024-04-20T13:32:23Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![djames](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/d/7ab992/32.png) [@djames](https://discourse.vtk.org/u/djames)
#### Post date: [April 20, 2024, 1:32pm UTC](https://discourse.vtk.org/t/how-do-i-construct-a-surface-bordered-by-two-perimeters/13758/1 "2024-04-20T13:32:23Z")

</div>

Below is a script that constructs a square perimeter with a triangle perimeter inside

I would like to construct a surface between the triangle and the square. Is there a way to do this without e.g. manually constructing vtkQuads or vtkTriangles?

```auto
import vtk

# Square points and lines
points = [
    [0, 0, 0],
    [1, 0, 0],
    [1, 1, 0],
    [0, 1, 0],
]
lines = [
    [0, 1],
    [1, 2],
    [2, 3],
    [3, 0],
]

# Inner triangle points and lines
points += [
    [0.25, 0.25, 0],
    [0.75, 0.25, 0],
    [0.5, 0.75, 0],
]
lines += [
    [4, 5],
    [5, 6],
    [6, 4],
]

num_points = len(points)
num_lines = len(lines)

# Create a cell array out of these points
edges = vtk.vtkCellArray()
for i in range(num_lines):
    line = vtk.vtkLine()
    line.GetPointIds().SetId(0, lines[i][0])
    line.GetPointIds().SetId(1, lines[i][1])
    edges.InsertNextCell(line)

# Create a polydata object
square = vtk.vtkPolyData()
square.SetPoints(vtk.vtkPoints())
square.SetLines(edges)

# Add the points to the dataset
for i in range(num_points):
    square.GetPoints().InsertPoint(i, points[i])

# Create a mapper
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(square)

actor = vtk.vtkActor()
actor.SetMapper(mapper)

renderer = vtk.vtkRenderer()
renderer.AddActor(actor)

renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)
renderWindow.SetWindowName("Square")

renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)

renderWindow.Render()
renderWindowInteractor.Start()

```