Create a new model

This guide builds the smallest useful IFC model: a slab and two walls in a storey, in a building, on a site, in a project. It follows sample 01 First building; download it from the samples page to see the finished definition.

If IFC is new to you, the IFC 4.3 documentation by buildingSMART explains the concepts used here.

How a model is built

In IfcHopper you build the model from the bottom up, like the IFC spatial structure:

objects → storey → building → site → project → model → file

Each component outputs an IfcHopper object that you connect to the component above it. Nothing is written until you write the model; until then the components only hold data, so you can change anything and see the result at once.

1. Objects

Make some geometry, e.g. three Center Box components (the floor slab and two walls), and connect each one to the Geometry input of an Object component. On each Object set:

• Class: the IFC class, e.g. IfcSlab or IfcWall. Any instantiable IFC element class works; an error lists what is wrong when it does not exist.
• Name: e.g. Floor slab, South wall.
• Type: the predefined type, e.g. FLOOR for the slab and SOLIDWALL for the walls. Other values are written as USERDEFINED with your value as object type.

Geometry is written as meshes: Breps, extrusions, surfaces and SubDs are faceted. Element parameters preview their geometry in the viewport.

2. Spatial structure

• Storey: connect the three objects to Elements and name it, e.g. Ground floor.
• Building: connect the storey to Storeys.
• Site: connect the building to Facilities.
• Project: connect the site to Sites and name it, e.g. First building.

Inputs you leave empty take defaults: names (Hopper Building, Hopper Site…), placements (the parent's), units (the Rhino document's) and GlobalIds. GlobalIds are derived from the component and the data, so writing again keeps the same ids.

A child its parent does not accept in IFC (e.g. a storey directly in a site) gives an error on the component.

3. Write

• Model: connect the project to Project. You can also give an author and an organisation for the file header.
• Write IFC: connect the model to Model, set the file Name (e.g. 01 First building.ifc) and the Directory (empty: an IfcHopper folder in your user folder; a relative path is taken from the folder of the saved definition), then set Write to true with a Boolean Toggle.

The Path output gives the full path of the file. Schema chooses IFC4X3_ADD2 (the default), IFC4 or IFC2X3.

The result

Open the file in any IFC viewer, or in a text editor. These are the lines IfcHopper wrote for the spatial structure and the objects:

FILE_SCHEMA (('IFC4X3_ADD2'));
#1=IFCPROJECT('2E5OFGAYvMBxjV_FRIL$Z_',$,'First building',$,$,$,$,(#7),#2);
#10=IFCSITE('1Kh9$mx$TT1Qvy7f4HIz$X',$,'Hopper Site',$,$,#11,$,$,.ELEMENT.,$,$,$,$,$);
#14=IFCBUILDING('0Vg46MsbfQb9l7Ktp2EWgT',$,'Hopper Building',$,$,#15,$,$,.ELEMENT.,$,$,$);
#18=IFCBUILDINGSTOREY('0UChqgxhTPExoTQm2pUrQR',$,'Ground floor',$,$,#19,$,$,.ELEMENT.,0.);
#22=IFCSLAB('0J1lEAucXTD9Xp4xbG6FBV',$,'Floor slab',$,$,#23,#128,$,.FLOOR.);
#129=IFCWALL('2eTALLc3vO9fb2zFqsYDwu',$,'South wall',$,$,#130,#210,$,.SOLIDWALL.);
#211=IFCWALL('2S4anjrHzHaPPs8Sg$UIVT',$,'North wall',$,$,#212,#306,$,.SOLIDWALL.);
#307=IFCRELCONTAINEDINSPATIALSTRUCTURE('0ziXlZJp9HjeiWsVCnb7X7',$,$,$,(#22,#129,#211),#18);
#308=IFCRELAGGREGATES('3HfPT63u5NX8km4XCRlB9X',$,$,$,#14,(#18));
#309=IFCRELAGGREGATES('1fILDxl41HVud8rVAGaY4s',$,$,$,#10,(#14));
#310=IFCRELAGGREGATES('0cwdWRw$nMAf3GoLeKIg1q',$,$,$,#1,(#10));

The objects are contained in the storey (IfcRelContainedInSpatialStructure) and the storey, building and site are aggregated (IfcRelAggregates), as IFC requires.

Next steps

• Add property sets with Pset, materials with Material, classifications with Classification: see samples 08 to 10.
• Use types and Rhino blocks for repeated objects: sample 07.
• Build infrastructure with Road, Bridge, Railway and their parts: sample 04.
• Read an existing model.