jikalulu
commented
1 year ago Hi Marc , these concepts originate from the CityGML conceptual model: The different Levels of Detail are defined in the following way.
LOD 0: Volumetric real-world objects (Spaces) can be spatially represented by a single point, by a set of curves, or by a set of surfaces. Areal real-world objects (Space Boundaries) can be spatially represented in LOD0 by a set of curves or a set of surfaces. LOD0 surface representations are typically the result of a projection of the shape of a volumetric object onto a plane parallel to the ground, hence, representing a footprint (e.g., a building footprint or a floor plan of the rooms inside a building). LOD0 curve representations are either the result of a projection of the shape of a vertical surface (e.g., a wall surface) onto a grounding plane or the skeleton of a volumetric shape of longitudinal extent such as a road or river segment. LOD 1: Volumetric real-world objects (Spaces) are spatially represented by a vertical extrusion solid, i.e., a solid created from a horizontal footprint by vertical extrusion. Areal real-world objects (Space Boundaries) can be spatially represented in LOD1 by a set of horizontal or vertical surfaces. LOD 2: Volumetric real-world objects (Spaces) can be spatially represented by a set of curves, a set of surfaces, or a single solid geometry. Areal real-world objects (Space Boundaries) can be spatially represented in LOD2 by a set of surfaces. The shape of the real-world object is generalized in LOD2 and smaller details (e.g., bulges, dents, sills, but also structures, like balconies or dormers of buildings) are typically neglected. LOD2 curve representations are skeletons of volumetric shapes of longitudinal extent like an antenna or a chimney. LOD 3: Volumetric real-world objects (Spaces) can be spatially represented by a set of curves, a set of surfaces, or a single solid geometry. Areal real-world objects (Space Boundaries) can be spatially represented in LOD3 by a set of surfaces. LOD3 is the highest level of detail and respective geometries include all available shape details. (those definitions come from the OGC documentation for CityGML
for more info about the LOD:
- documentation section 6.4. CityGML Core Model: Space Concept, Levels of Detail, Special Spatial Types, for the conceptual ideas.
- documentation 7.2.5. Geometry and LOD , for the definitions
MarcBruyland
bahimc
The definitions contain terms that are not clear.
BuildingGeometry: 2D and 2.5D (2D=2 dimensions; 2.5D ???) BuildingGeometry3DLoD1: LoD1 representation ? (what's the difference with LoD2 ?) BuildingGeometry3DLoD2: LoD2 representation ? (what's the difference with LoD1 ?)