# [Gmsh] Different Geometry Behaviour Using Default and OpenCascade

```Hello everybody,

I need your help on explaining me a different behaviour while using default
geometry and OpenCascade geometry. Eventually I will depend on using
OpenCascade to be able to use Boolean Operators. I automatically generate
the Geometry from a CityGML File. Here is what it looks like by Default:```
```
Point(0) = {361597.281, 5721167.500, 45.926};
Point(1) = {361598.062, 5721158.500, 45.926};
Point(2) = {361598.062, 5721158.500, 42.642};
Point(3) = {361597.281, 5721167.500, 42.642};
Line(0) = {0, 1};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 0};
Line Loop(0) = {0, 1, 2, 3};
Plane Surface(0) = {0};
Point(4) = {361591.594, 5721158.000, 45.926};
Point(5) = {361591.594, 5721158.000, 42.642};
Line(4) = {1, 4};
Line(5) = {4, 5};
Line(6) = {5, 2};
Line Loop(1) = {4, 5, 6, -1};
Plane Surface(1) = {1};
Point(6) = {361590.844, 5721167.000, 45.926};
Point(7) = {361590.844, 5721167.000, 42.642};
Line(7) = {4, 6};
Line(8) = {6, 7};
Line(9) = {7, 5};
Line Loop(2) = {7, 8, 9, -5};
Plane Surface(2) = {2};
Line(10) = {6, 0};
Line(11) = {3, 7};
Line Loop(3) = {10, -3, 11, -8};
Plane Surface(3) = {3};
Point(8) = {361594.844, 5721158.500, 48.838};
Line(12) = {1, 8};
Line(13) = {8, 4};
Line Loop(4) = {-4, 12, 13};
Plane Surface(4) = {4};
Point(9) = {361594.062, 5721167.500, 48.838};
Line(14) = {6, 9};
Line(15) = {9, 0};
Line Loop(5) = {-10, 14, 15};
Plane Surface(5) = {5};
Line(16) = {9, 8};
Line Loop(6) = {0, 15, -16, 12};
Plane Surface(6) = {6};
Line Loop(7) = {-7, -13, -16, -14};
Plane Surface(7) = {7};
Line Loop(8) = {-2, -6, -9, -11};
Plane Surface(8) = {8};
Surface Loop(0) = {0, 1, 2, 3, 4, 5, 6, 7, 8};
Volume(0) = {0};
Point(9000) = {361580.844, 5721148.000, 42.642, 10.000};
Point(9001) = {361608.062, 5721148.000, 42.642, 10.000};
Point(9002) = {361608.062, 5721177.500, 42.642, 10.000};
Point(9003) = {361580.844, 5721177.500, 42.642, 10.000};
Point(9004) = {361580.844, 5721148.000, 58.838, 10.000};
Point(9005) = {361608.062, 5721148.000, 58.838, 10.000};
Point(9006) = {361608.062, 5721177.500, 58.838, 10.000};
Point(9007) = {361580.844, 5721177.500, 58.838, 10.000};
Line(9901) = {9000, 9001};
Line(9902) = {9001, 9002};
Line(9903) = {9002, 9003};
Line(9904) = {9003, 9000};
Line(9905) = {9000, 9004};
Line(9906) = {9001, 9005};
Line(9907) = {9002, 9006};
Line(9908) = {9003, 9007};
Line(9909) = {9004, 9005};
Line(9910) = {9005, 9006};
Line(9911) = {9006, 9007};
Line(9912) = {9007, 9004};
Line Loop(9990) = {9901, 9902, 9903, 9904};
Plane Surface(9990) = {9990};
Line Loop(9991) = {9901, 9906, -9909, -9905};
Plane Surface(9991) = {9991};
Line Loop(9992) = {-9906, 9902, 9907, -9910};
Plane Surface(9992) = {9992};
Line Loop(9993) = {-9907, 9903, 9908, -9911};
Plane Surface(9993) = {9993};
Line Loop(9994) = {-9908, 9904, 9905, -9912};
Plane Surface(9994) = {9994};
Line Loop(9995) = {9909, 9910, 9911, 9912};
Plane Surface(9995) = {9995};
Surface Loop(9999) = {9990, 9991, 9992, 9993, 9994, 9995};
Volume(9999) = {9999};

This is working without problems when I open it I gmsh giving no errors.
When I trying to use OpenCascade I get the following errors:

Error   : OpenCASCADE wire or line loop with tag 5 already exists
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 38 : Could not add line loop
Error   : Could not create face
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 42 : Could not add plane
surface
Error   : Could not create face
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 44 : Could not add plane
surface
Error   : Unknown OpenCASCADE face with tag 6
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 47 : Could not add surface loop
Error   : Unknown OpenCASCADE surface loop with tag 0
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 48 : Could not add volume
Error   : OpenCASCADE wire or line loop with tag 9993 already exists
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 75 : Could not add line loop
Error   : OpenCASCADE wire or line loop with tag 9995 already exists
Error   : 'LoD2_361_5721_1_NW.gml.geo', line 79 : Could not add line loop

Thank you very much for your help!

Max
```
```_______________________________________________
gmsh mailing list
gmsh@onelab.info
http://onelab.info/mailman/listinfo/gmsh
```