# Missing a surface when fragmenting

**URL:** <https://fenicsproject.discourse.group/t/missing-a-surface-when-fragmenting/11506>\
**Category:** mesh\
**Created:** [June 14, 2023, 8:56am UTC](https://fenicsproject.discourse.group/t/missing-a-surface-when-fragmenting/11506 "2023-06-14T08:56:59Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Mishal](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/mishal/32/7396_2.png) [@Mishal](https://fenicsproject.discourse.group/u/Mishal)\
**Post date:** [June 14, 2023, 8:56am UTC](https://fenicsproject.discourse.group/t/missing-a-surface-when-fragmenting/11506/1 "2023-06-14T08:56:59Z")

</div>

Hi Guys

Please refer to the below code.  
I have a few circles which are fragmented there after I need a line of nodes which pass through the center of the circles.

The below code is able to to develop that line of nodes for all surfaces expect one as per the attached image. Is there anything that I am missing or doing wrong?

```auto
import gmsh
import sys
import meshio

###User inputs
R_overhang = 10 
R_tank = 9
R1 = 8
R2 = 7
R3 = 5
R4 = 3

gmsh.initialize()

# #R_overhand
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R_overhang,1,0)
gmsh.model.occ.addCurveLoop([1] ,2)
gmsh.model.occ.addPlaneSurface([2],1)
#R_tank
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R_tank,3)
gmsh.model.occ.addCurveLoop([3] ,4)
gmsh.model.occ.addPlaneSurface([4],2)
#R1
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R1,5)
gmsh.model.occ.addCurveLoop([5] ,6)
gmsh.model.occ.addPlaneSurface([6],3)
#R2
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R2,7)
gmsh.model.occ.addCurveLoop([7] ,8)
gmsh.model.occ.addPlaneSurface([8],4)
#R3
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R3,9)
gmsh.model.occ.addCurveLoop([9] ,10)
gmsh.model.occ.addPlaneSurface([10],5)
#R4
gmsh.model.occ.addCircle(0.0, 0.0, 0.0,R4,11)
gmsh.model.occ.addCurveLoop([11] ,12)
gmsh.model.occ.addPlaneSurface([12],6)

gmsh.model.occ.addPoint(R_overhang,0,-0.1,1,13)
gmsh.model.occ.addPoint(R_overhang,0,0.1,1,14)
gmsh.model.occ.addPoint(-R_overhang,0,-0.1,1,15)
gmsh.model.occ.addPoint(-R_overhang,0,0.1,1,17)
gmsh.model.occ.addLine(13,14,18)
gmsh.model.occ.addLine(14,17,19)
gmsh.model.occ.addLine(17,15,20)
gmsh.model.occ.addLine(15,13,21)
gmsh.model.occ.addCurveLoop([18,19,20,21] ,13)
gmsh.model.occ.addPlaneSurface([13],7)

#Fragmenting surfaces
frag = gmsh.model.occ.fragment([(2,1)],[(2,2)])
print(frag)
frag = gmsh.model.occ.fragment([(2,2)],[(2,3)])
print(frag)
frag = gmsh.model.occ.fragment([(2,3)],[(2,4)])
print(frag)
frag = gmsh.model.occ.fragment([(2,4)],[(2,5)])
print(frag)
frag = gmsh.model.occ.fragment([(2,5)],[(2,6)])
print(frag)

frag = gmsh.model.occ.fragment([(2,7)],[(2,6)])
print(frag)
frag = gmsh.model.occ.fragment([(2,7)],[(2,8)])
print(frag)
frag = gmsh.model.occ.fragment([(2,7)],[(2,9)])
print(frag)
frag = gmsh.model.occ.fragment([(2,7)],[(2,10)])
print(frag)
frag = gmsh.model.occ.fragment([(2,7)],[(2,11)])
print(frag)
frag = gmsh.model.occ.fragment([(2,7)],[(2,12)])
print(frag)

gmsh.model.occ.synchronize()
gmsh.option.setNumber('Mesh.MeshSizeMin', 0.5)
gmsh.option.setNumber('Mesh.MeshSizeMax', 0.5)

gmsh.model.mesh.generate(2)
gmsh.model.mesh.recombine()
gmsh.option.setNumber("Mesh.SubdivisionAlgorithm", 1)
gmsh.model.mesh.refine()

gmsh.write("Circle.msh")
if '-nopopup' not in sys.argv:
    gmsh.fltk.run()

gmsh.finalize()

```

 ![Capture](https://global.discourse-cdn.com/free1/uploads/fenicsproject1/original/2X/4/45c10a728746a0e42c213bd78c9d586011e5e766.png)

---

<div class="post-metadata">

**Author:** ![conpierce8](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/conpierce8/32/2464_2.png) [@conpierce8](https://fenicsproject.discourse.group/u/conpierce8)\
**Post date:** [June 14, 2023, 6:32pm UTC](https://fenicsproject.discourse.group/t/missing-a-surface-when-fragmenting/11506/2 "2023-06-14T18:32:50Z")

</div>

You can pass multiple objects and tools to `fragment`. Also, you can fragment using lower-dimensional entities, such as lines:

```python
import gmsh
import sys

# import meshio

###User inputs
R_overhang = 10
R_tank = 9
R1 = 8
R2 = 7
R3 = 5
R4 = 3

gmsh.initialize()

# #R_overhand
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R_overhang, 1, 0)
gmsh.model.occ.addCurveLoop([1], 2)
gmsh.model.occ.addPlaneSurface([2], 1)
# R_tank
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R_tank, 3)
gmsh.model.occ.addCurveLoop([3], 4)
gmsh.model.occ.addPlaneSurface([4], 2)
# R1
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R1, 5)
gmsh.model.occ.addCurveLoop([5], 6)
gmsh.model.occ.addPlaneSurface([6], 3)
# R2
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R2, 7)
gmsh.model.occ.addCurveLoop([7], 8)
gmsh.model.occ.addPlaneSurface([8], 4)
# R3
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R3, 9)
gmsh.model.occ.addCurveLoop([9], 10)
gmsh.model.occ.addPlaneSurface([10], 5)
# R4
gmsh.model.occ.addCircle(0.0, 0.0, 0.0, R4, 11)
gmsh.model.occ.addCurveLoop([11], 12)
gmsh.model.occ.addPlaneSurface([12], 6)

gmsh.model.occ.addPoint(R_overhang, 0, 0, 1, 13)
gmsh.model.occ.addPoint(-R_overhang, 0, 0, 1, 14)
gmsh.model.occ.addLine(13, 14, 18)

# Fragmenting surfaces
frag = gmsh.model.occ.fragment([(2, 1)], [(2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (1, 18)])

gmsh.model.occ.synchronize()
gmsh.option.setNumber('Mesh.MeshSizeMin', 0.5)
gmsh.option.setNumber('Mesh.MeshSizeMax', 0.5)

gmsh.model.mesh.generate(2)
gmsh.model.mesh.recombine()
gmsh.option.setNumber("Mesh.SubdivisionAlgorithm", 1)
gmsh.model.mesh.refine()

gmsh.write("Circle.msh")
if '-nopopup' not in sys.argv:
    gmsh.fltk.run()

gmsh.finalize()

```