Customizing BIM quantities

Commands

BIMPROPERTIES

About

Entities have a set of properties which can be viewed in the Properties Panel. If an entity has been assigned a certain BIM classification or Type (e.g. Wall or Slab), additional properties will be displayed such as IFC Common properties and Base quantities. Which properties are displayed in the panel is managed in the BIM Properties dialog, which is opened by the BIMPROPERTIES command.

Namespaces

In the BIM Properties dialog, by default three namespaces are available: IFC2x3 (1), Quantity (2) and User (3). The IFC2x3 namespace contains properties that are defined by the IFC2x3 schema. This contains both common properties (e.g. Wall Common properties, such as Fire Rating and Acoustic Rating), and Quantities (e.g. Wall Quantity > Nominal lenght (4)). These Quantities are based on so-called Core quantities (5) of the solid. See Core quantities for more information.

The Quantity namespace contains some hard-coded quantities of BIM objects also based on the Core quantities, much like in the IFC2x3 namespace.
Note: This Quantity namespace is deprecated. It has been replaced by the Quantities in the IFC2x3 namespace, however it is still available in the BIM Properties dialog for backward compatibility with versions V20 and older.

The User namespace exists for the user to create their own property definitions. See also the Procedure article Custom Properties for more information on custom properties.

It is also possible to import namespaces, e.g. the IFC4 namespace. This can be done by clicking the Import button (6) on the bottom left.


Note: using this method the namespace will only be imported for this particular project. If you want namespaces to be imported over all your projects, open the Settings dialog and under the BIMGeneralDefault properties path you can add a new path. By default, it should take you to C:\Program Files\Bricsys\BricsCAD Vxx en_US\Support, where you can find for instance the bimproj_IFC4.xml containing the IFC4 namespace.

Core quantities

Core quantities are quantities of solids that are calculated based on the geometric features of that solid, and that can be used in user-defined quantities. These core quantities are also the basis for the quantities defined in the IFC2x3 and IFC4 properties as described in the previous section.

For example, under Wall Quantities in the IFC2x3 namespace, the Nominal Height of a wall is defined as the ZDimUpBoundingBox of the solid, which is a Core quantity. A full list of Core quantities can be found below.
Core Quantity Description Measure Type
NumberOfPlies Number of plies in the attached composition. Integer
XDimUpBoundingBox X dimension of the bounding box found with global Z axis rotation freedom. Length Real
YDimUpBoundingBox Y dimension of the bounding box found with global Z axis rotation freedom. Length Real
ZDimUpBoundingBox Z dimension of the bounding box found with global Z axis rotation freedom. Length Real
XDimFreeBoundingBox X dimension of the bounding box found with 3D rotation freedom. Length Real
YDimFreeBoundingBox Y dimension of the bounding box found with 3D rotation freedom. Length Real
ZDimFreeBoundingBox Z dimension of the bounding box found with 3D rotation freedom. Length Real
DistanceBetweenMajorSurfaces Distance between major surfaces. Length Real
FirstMajorSurfacePerimeter Perimeter of the first (largest) major surface. Length Real
SecondMajorSurfacePerimeter Perimeter of the second major surface. Length Real
LinearAxisLength Length of the linear element's axis. Length Real
VariablePlyThickness Thickness of a variable ply. Length Real
FirstMajorSurfaceNetArea Area of the first (largest) major surface after subtracting openings. Area Real
FirstMajorSurfaceGrossArea Area of the first (largest) major surface before subtracting openings. Area Real
SecondMajorSurfaceNetArea Area of the second major surface after subtracting openings. Area Real
SecondMajorSurfaceGrossArea Area of the second major surface before subtracting openings. Area Real
IsMajorSurfacesParallel Indicator if the major surfaces are parallel. Boolean
TotalSurfaceNetArea Area of the solid's surfaces after subtracting openings. Area Real
TotalSurfaceGrossArea Area of the solid's surfaces before subtracting openings. Area Real
FootprintNetArea Area of the bottommost solid's surfaces after subtracting openings. Area Real
FootprintGrossArea Area of the bottommost solid's surfaces before subtracting openings. Area Real
ProjectedNetArea Area of the solid's surfaces projected to global XY plane after subtracting openings. Area Real
ProjectedGrossArea Area of the solid's surfaces projected to global XY plane before subtracting openings. Area Real
CrossSectionNetArea Area of the cross section for linear elements after subtracting openings. Area Real
OuterSurfaceNetArea Area of the outer surface for linear elements after subtracting openings. Area Real
NetVolume Volume of the solid after subtracting openings. Volume Real
GrossVolume Volume of the solid before subtracting openings. Volume Real

User-defined quantities

In the User namespace it is possible to create custom properties inside a custom property set using the Property (7) button, see Procedure article Custom Properties.

It is also possible to create user-defined quantities, using the Value (8) button. In the image below, a user-defined quantity was created in a custom property set (9). This user-defined quantity (or Value Definition) has the following attributes:
  • Id (10): a unique identifier.
  • Label (11): the name of quantity which will show up in the properties panel. This can be the same as the ID, however the ID must be unique.
  • Description (12): a description of the quantity.
  • Type (13): the type of the quantity. Typically, a quantity will be defined as a Real value.
  • Measure (14): the measure of the quantity, i.e. is it a length value, an area, volume or mass?
  • Formula (15): the actual expression of the quantity. Here Core quantities can be used, as well as mathematical expressions as defined in the Procedure article Working with Parameters and Constraints.
In this example, a user-defined quantity is defined that displays half the thickness of a wall, which is calculated as DistanceBetweenMajorSurfaces/2.


Procedure: creating a user-defined quantity

In this part you will learn how to make user-configurable quantities. By way of example, we will define a quantity of Spatial objects such as a room. The quantity will be the Compactness which can be calculated as the volume of the space divided by the sum of the areas on all sides of the space.



  1. Open the BIM Properties dialog by typing BIMPROPERTIES in the Command line.
  2. Set the User namespace as current namespace.
  3. Create a new Property Set by clicking the Set button (16), and give it a name (17).
  4. Assign the Property Set to one or more categories (18). In this example we will assign it to spatial elements.
  5. Create a new Value Definition by clicking the Value button (19).
  6. Give this Value Definition an Id and a Label, e.g. Compactness.
  7. (Optional) Give this Value Definition a description.
  8. Assign the correct Type to this Value Definition. Because our Value Definition will be based on a calculation of two Real values, this will also be a Real value.
  9. Assign a Measure to the Value Definition. Because the result of the calculation will be a volume divided by an area, we will end up with a Length measure.
  10. Fill in an expression in the Formula field. The volume of a space is a Core quantity with the name GrossVolume. The sum of areas of the space on all sides is also a Core quantity with the name TotalSurfaceGrossArea. Hence, we can define the Compactness = GrossVolume/TotalSurfaceGrossArea.


  11. Click OK to close the BIM Properties dialog.
  12. Create a volume that represents a space, either by creating surrounding elements like walls and a slab, and by defining a space inside using the BIMSPACE or BIMIFY commands, or by creating a solid and using BIMCLASSIFY to classify it as a Space.
  13. Select the space. In the BIM Properties panel you should now see your user-defined property under a separate property set.