CityGML is an open standardized data model and exchange format to store digital 3D models of cities and landscapes. It defines ways to describe most of the common 3D features and objects found in cities (such as buildings, roads, rivers, bridges, vegetation and city furniture). It supports several levels of details and supports materials and textures. 3D features have standardized attributes based on their type (building, road, bridge) and support additional user attributes.
CityJSON is a different exchange format which uses the same underlying data model as CityGML. Both formats can be imported into the Tygron Platform.
Currently the Tygron Platform supports the import of the following modules of the CityGML standard:
- Building (and class BuildingPart)
- Bridge ( and class BridgePart )
- CityObjectGroup (containing other Buildings, BuildingParts, Bridges, BridgeParts and CityObjectGroups)
Each Building, BuildingPart, Bridge and BridgePart can contain one or more surfaces. These surfaces are used to create a 2-dimensional polygon for a feature (Building in the Tygron Platform) and 3-dimension Custom Geometries for visualization. Unsupported surfaces are not processed. The surface types that are currently supported by the Tygron Platform are:
- Polygon (gml geometry types such as LineStrings and Polygons)
- CompositeSurface (that contains Polygons and other CompositeSurfaces)
Level of Detail
Each building part can contain multiple LODs (Level of Detail). Currently only one is selected for each surface, based on the following preference:
- LoD 2
- LoD 3
- LoD 1
- LoD 4
- LoD 0
Texture and Color
Each surface can be textured with 1 image. If the surface is not textured, a color is obtained for the surface when the surface has X3DMaterial surface data. Of a X3DMaterial, the color (including transparency) is picked based on the first occurrence of:
- Diffuse color
- Specular color
- Emissive color
A white color is the fallback color when none of the colors are specified in any X3DMaterials associated with the surface.
- Other modules are not read when importing with the Geo Data Wizard.
- These 3D Models will be stored in the project as Custom Geometries. These Custom Geometries can be automatically assigned to buildings present in the project based on their location.
- How to import 3D BAG data
- How to import a CityGML/CityJSON file
- How to import a CityGML/CityJSON file for 2D Spatial data
- Converting a Sketchup model to CityGML format
- Exporting Blender models to CityJSON
- T. H. Kolbe, T. Kutzner, C. S. Smyth, C. Nagel, C. Roensdorf, C. Heazel ∙ OGC City Geography Markup Language (CityGML) Part 1: Conceptual Model Standard ∙ found at: https://docs.ogc.org/is/20-010/20-010.html (last visited 2024-02-07)