# IFC Export format - September 28, 2021

###### tags: `pipeline` `export` `ifc`

This document intends to provide a technical overview of the current Archilyse IFC export format.

## Export Format

### Hierarchy

graph LR;
    subgraph Spatial Structure;
        Site(IfcSite)--"IfcRelAggregates"-->Building;
        Building(IfcBuilding)--"IfcRelAggregates"-->Floor;
        Floor(IfcBuildingStorey)--"IfcRelAggregates"-->Area(IfcSpace);
        Unit(IfcSpatialZone)--"IfcRelAggregates"-->Area;
    end;

    Floor--"IfcRelContainedInSpatialStructure"-->Wall(IfcWall);
    Floor--"IfcRelContainedInSpatialStructure"-->Railing(IfcRailing);
    Wall--"IfcRelVoidsElement"-->Opening(IfcOpening);
    Opening--"IfcRelFillsVoid"-->Door(IfcDoor);
    Opening--"IfcRelFillsVoid"-->Window(IfcWindow);
    Area--"IfcRelContainedInSpatialStructure"-->SanitaryTerminal(IfcSanitaryTerminal);
    Area--"IfcRelContainedInSpatialStructure"-->Furniture(IfcFurniture);
    Floor--"IfcRelContainedInSpatialStructure"-->Slab(IfcSlab);
    Area--"IfcRelContainedInSpatialStructure"-->Stair(IfcStair);

### Supported Elements

| Archilyse Terminology | Archilyse SubType | IFC Type | Name |
| --------- | ------- | --- | --|
| *Structural Elements* |
| Site | * | IfcSite | {client_site_id} |
| Building | * | IfcBuilding | {street} {housenumber} |
| Floor | * | IfcBuildingStorey | Floor {floor_number} |
| Unit | * | IfcSpatialZone | {client_unit_id} |
| Area | * | IfcSpace | {classification_scheme_area_type}-{floor_number}.{area_number_in_floor} |
| *Building Elements* |
| Separator | Wall | IfcStandardWallCase | Wall |
| Separator | Railing | IfcRailing | Railing |
|||
| Opening | Window | IfcWindow | Window |
| Opening | Door | IfcDoor | Door |
| Opening | Entrance Door | IfcDoor | Entrance_door |
|||
| Feature | Stair | IfcStair | Stairs |
| Feature | Bathtub | IfcSanitaryTerminal | Bathtub |
| Feature | Toilet | IfcSanitaryTerminal | Toilet |
| Feature | Shower | IfcSanitaryTerminal | Shower |
| Feature | Sink | IfcSanitaryTerminal | Sink |
| Feature | Kitchen | IfcFurniture | Kitchen |

### Geometries

* Metric
* Georeferencing via site location
* Otherwise just absolute coordinates except a few other cases

| Element | Placemnent Relative To (X, Y, Z) | Geometry (z_min, z_max) |
| ------- | ---------- | -------- |
| *Structural Elements* | | |
| IfcSite | (0, 0, 0)) | - |
| IfcBuilding | IfcSite (0, 0, 0) | - |
| IfcBuildingStorey | IfcBuilding (0, 0, FloorNumber*FloorHeight) | |
| Area | Floor (0, 0, 0) | ExtrudedAreaSolid (0, Wallheight) |
| *Building Elements* | | |
| IfcWall | IfcBuildingStorey (0, 0, 0) | ExtrudedAreaSolid (0, WallHeight) |
| IfcRailing | IfcBuildingStorey (0, 0, 0) | ExtrudedAreaSolid (0, RailingHeight) |
| IfcSlab | IfcBuildingStorey (0, 0, WallHeight \| -WallThickness) | ExtrudedAreaSolid (0, FloorThickness) |
| IfcStair | IfcBuildingStorey (0, 0, 0) | ExtrudedAreaSolid (0, WallHeight) |
| IfcOpening | IfcWall (0, 0, 0) | ExtrudedAreaSolid |
| IfcWindow | IfcWall (0, 0, 0) | ExtrudedAreaSolid |
| IfcDoor | IfcWall (0, 0, 0) | ExtrudedAreaSolid |
| IfcFurniture | IfcBuildingStorey (0, 0, 0) | ExtrudedAreaSolid |
| IfcSanitaryTerminal | IfcBuildingStorey (0, 0, 0) | MappedSurfaceModel |

### Properties

| Element | PropertySet | Property | Description |
| -- | -- | -- | -- |
| *Structural Elements* |
| IfcSpace | PSet_SpaceCommon | PublicallyAccessible ||
| IfcSpace | PSet_SpaceCommon | Reference | SIA416 |

### Quantities

| Element | QuantitySet | Quantity | Description | Notes |
| -- | -- | -- | -- | -- |
| *Structural Elements* |
| IfcSpace | Qto_SpaceBaseQuantities | Height |||
| IfcSpace | Qto_SpaceBaseQuantities | GrossPerimeter |||
| IfcSpace | Qto_SpaceBaseQuantities | NetFloorArea |||
| IfcSpace | Qto_SpaceBaseQuantities | NetVolume |||
| *Building Elements* |
| IfcDoor | Qto_DoorBaseQuantities | Width |||
| IfcDoor | Qto_DoorBaseQuantities | Height |||
| IfcDoor | Qto_DoorBaseQuantities | Perimeter |||
| IfcDoor | Qto_DoorBaseQuantities | Area |||
| IfcWindow | Qto_WindowBaseQuantities | Width |||
| IfcWindow | Qto_WindowBaseQuantities | Height |||
| IfcWindow | Qto_WindowBaseQuantities | Perimeter |||
| IfcWindow | Qto_WindowBaseQuantities | Area |||

### Materials

Currently no materials are being used.

## Implementation

* We differentiate between mappers which map Python datatypes to IFC datatypes and generators which generate IFC datatypes.
* Three main generators:
- IfcProductGenerator
- IfcRelationshipGenerator
- IfcGeometricRepresentationItemGenerator
* Mappers:
- EntityIfcMapper is top-level generator that maps our internal structures (brooks/db) to IFC
- delegates geometry creation to GeometryIfcMapper
- delegates materials, properties and quantities to MaterialIfcMapper, PropertyIfcMapper and QuantityIfcMapper, respectively.

graph LR;

subgraph Generators;
    IfcRootGenerator;
    IfcProductGenerator;
    IfcRelationshipGenerator;
    IfcGeometricRepresentationItemGenerator;

    IfcProductGenerator --inherits--> IfcRootGenerator;
    IfcRelationshipGenerator --inherits--> IfcRootGenerator;
    IfcGeometricRepresentationItemGenerator --inherits--> IfcRootGenerator;
end;

subgraph Mappers;
    EntityIfcMapper;
    GeometryIfcMapper;
    MaterialIfcMapper;
    PropertyIfcMapper;
    QuantityIfcMapper;

    EntityIfcMapper --> GeometryIfcMapper;
    EntityIfcMapper --> PropertyIfcMapper;
    EntityIfcMapper --> QuantityIfcMapper;
    EntityIfcMapper --> MaterialIfcMapper;
end;

GeometryIfcMapper --> IfcGeometricRepresentationItemGenerator;
MaterialIfcMapper --> IfcRelationshipGenerator;
PropertyIfcMapper --> IfcRelationshipGenerator;
QuantityIfcMapper --> IfcRelationshipGenerator;
EntityIfcMapper --> IfcProductGenerator;
EntityIfcMapper --> IfcRelationshipGenerator;