EN/CityGML-Tutorial/chapter-2:-Building/LOD1.md

@@ -6,7 +6,21 @@ In LOD1, buildings are represented as block models or by simple extrusion of hei
 
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-For the geometries of a LOD1 building, the CityGML 2.0 standard allows the use of MultiSurface or Solid elements. However, a MultiSurface geometry does not guarantee the necessary topological connection of its surfaces. To prevent this, it is recommended that only solid geometries be used for LOD1 buildings.
+For the geometries of a LOD1 building, the CityGML 2.0 standard allows the use of MultiSurface or Solid elements. However, a MultiSurface geometry does not guarantee the necessary topological connection of its surfaces. To prevent this, it is recommended that only solid geometries be used for LOD1 buildings. Below figure shows a LoD1 building with solid geometry directly containing the bounding geometry.
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+<div align=center>
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+![image](uploads/9f320e1dd0f8f3e722a0c280c270bbcd/image.png)
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+</div>
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+<div align=center>
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+**A LoD1 Building with Solid Geometry**[^1]
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+</div>
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+[^1]: [SIG3D Modeling Guide for 3D Objects - Part 2: Modeling of Buildings (LoD1, LoD2, LoD3)](https://en.wiki.quality.sig3d.org/index.php?title=Modeling_Guide_for_3D_Objects_-_Part_2:_Modeling_of_Buildings_(LoD1,_LoD2,_LoD3)#Building_.28bldg:Building.29)
 
 An XML document of a CityGML 2.0 LOD1 building will look like this: