DesignBuilder provides interoperability with BIM models through its gbXML import capability. This allows you to import 3-D architectural models created in Revit, ArchiCAD or Microstation and other BIM systems supporting gbXML data exchange.
To import gbXML data you should first create a building with no blocks, then click on File > Import > Import BIM/gbXML model. This opens the Import 3-D CAD Model dialog.
Unlike the 2-D floor plan import which provides only a set of lines for tracing over, importing 3-D CAD data imports the full geometry as blocks with zones, shading surfaces, windows, doors etc.
This dialog has two pages. On the first page you can select the xml file to import. Once you have selected the model, press the Next button to move to the second page. For large models there will be a delay at this point while the xml data is loaded. The second page shows a simple thumbnail view of the gbXML data along with some simple controls to control the way the import is to be carried out.
You can display the thumbnail of the gbXML data from various viewpoints. Select from:
The is the maximum gap between neighbouring parallel gbXML surfaces that will be interpreted as being an adjacency between 2 spaces. You might enter a value higher than the default 0.01m if the gbXML spaces are separated by large gaps due to thick partitions or ceiling /floor voids being excluded from the gbXML. For example if the largest gap in the between spaces that are to be modelled as adjacent is 0.3m then enter 0.3m here.
The Adjacency tolerance can also be updated after the import from the Advanced tab of the Model options dialog.
By default this option is selected and the geometric space data will be imported as building blocks ready for use in DesignBuilder modelling.
You can instead import BIM space geometry as outline blocks by unchecking this option. The outline blocks give an exact representation of the gbXML spaces in the gbXML and this can be useful for diagnosing problems with poor gbXML, For example if any part of a space intersects with another space then it would not created as a building block but it could be created as an outline block.
If this option is selected then DesignBuilder will any load materials, constructions and glazing system thermal properties present in the BIM model and assign them to surfaces and windows in the model.
Shading surfaces are specially marked in gbXML data and so can be treated separately if required. You can choose to import shading surfaces as part of the import or not using this control. Shading surfaces imported through gbXML will be 2-D flat shading surfaces.
If the above Import shading surfaces option is selected then you can choose to either merge any such co-planar surfaces or not.
Example gbXML imported from Revit into DesignBuilder
Example gbXML imported from ArchiCAD into DesignBuilder
The geometric information contained in gbXML includes a collection of space objects which represent the inner volumes of rooms in the parent BIM model. These space objects aren’t native to the BIM system but are identified manually by users generally using some form of manual or semi-automatic process. Contrary to expectation, no native geometry is actually exported to gbXML from the BIM system. The result of the spatial identification process is a collection of spaces that are separated by gaps that would be filled in the parent BIM model by the BIM primitives such as partitions, slabs, etc.
The adjacency between neighbouring surfaces is calculated within DesignBuilder based on the Separation tolerance setting.
The DesignBuilder gbXML import works by simply mapping the gbXML space geometry to building blocks, one block per zone. Blocks represents space inner geometry so the Internal measurements Geometry convention template is applied to give zero thickness for all block surfaces.
Note: It is important to understand that the success of the BIM to DesignBuilder data transfer process depends on how well the spatial identification process has been conducted in the BIM system. If there are intersecting or missing spaces in the BIM model then the model imported into DesignBuilder will also have problems.
There is a DesignBuilder plugin for the most recent versions of Revit, which can help to ease the workflow when transferring BIM models from Revit to DesignBuilder. This is installed with DesignBuilder. The version of Revit you wish to use must be installed at the time you install DesignBuilder.
You can read how to get the most from the Revit to DesignBuilder link in DesignBuilder Revit – gbXML Tutorial.