From constructive solid geometry (CSG) model, the concept of parameters emerged quite early with 3D modelling. However, the initial functionality and capabilities were very limited. A clearer need for parametric modelling emerged only with properties. One of the first properties we can detect in spatial modelling CAD systems is materiality (Sacks, R. et al. 2018). It emerged naturally early on, because in order to combine the individual geometric shapes into a new volume by Boolean operations, it became apparent that the way in which the two geometric shapes were connected also depended on the materiality of the elements of their representation. It is not difficult to combine two geometric shapes of the same material. The challenge arises when it comes to deciding which form or primitive to prioritize in the case of materiality.
This perception later developed Boolean operations and the very concepts of spatial modelling and BIM, that modelling takes place by combining features and geometry into an initial basic volume or element.
An example of this in the field of construction is reinforced concrete precast wall panels or other reinforced concrete precast elements. They consist of many separate components, such as fittings, reinforcement, separate layers of insulation and other elements, all of which merely connect to the main reinforced concrete element (Figure 6). The materiality of these components differs from the basic element.
This example illustrates several important aspects related to BIM and spatial modelling. In the real world, everything is interconnected not only geometrically but also by its properties, which depend on the other components around it.
The first principles of parametric modelling emerged, the realization that individual volumes can share a common parameter, as in the example case mentioned – the dimensions of the insulation layer and reinforced concrete slabs. Nowadays, in BIM platforms, it is quite natural that everything is interconnected – the height of the columns with the floor slabs, the height of the walls to the floor, the bottom of the door to the floor, and so on. The perception and emergence of these relationships in the concept of parametric modelling paved the way for a more realistic representation of the built-up space in computer programs, more convenient and faster work. It also gave rise to the emergence of structures for construction objects and all structures, according to the standard. This parametric modelling was not limited to geometry to represent real physical objects, but also touched on various auxiliary and annotation elements such as axis networks, footnotes, and so on. Thus, parametric modelling has made it possible to globally control and perform geometric changes to static models by controlling only a few individual parameters.
It is possible to dynamically edit BIM models in different BIM softwarse depending on the design stage.
Instead of controlling ordinary numbers, in creating geometry, it became possible to link two geometric elements and later objects, describing their individual points, lines or surfaces as being parallel, perpendicular to other geometric primitives, respectively.
Modern 3D CAD and BIM software has greatly expanded the concept of parametric modelling, where parametric relationships are used now to generate complete model sections, annotation elements, such as dimensions, coordinates, and so on.
However, parametric modelling differs from standard 3D CAD modelling as objects such as primitive shapes are associated with parameters or variables that can instantly change the geometry or other properties of an object. Simple parameters of an object may include an object’s length, width, height or radius. Other more complex parametric objects may have parameters that can change the entire structure or geometry of an object depending on different conditions. Parameters of an object can also control the location of an object within a larger model. Parametric library objects (such as doors or windows) allow objects to be reused multiple times in a model or in many different models with varying parameters. This approach is very efficient for modelling elements that are repeated but may contain geometric variation between different instances.
Parametric modelling enables the user to make the necessary changes quickly and fully automate entire digital modelling processes. This is how many modern BIM platforms work, as it automatically sequence the various interfaces between elements, geometry, and annotation components without actively involving the user.
Despite the differences, a modern parametric CAD or BIM system has the following features:
The more recent development of the concept Building Information Modelling (BIM) incorporates the main developments in 3D modelling including parametric and feature-based modelling combined with a dynamic 3D database for storing information relating to buildings. The addition of a dynamic relational database for building elements (similar to a Geographic Information System) enables many new applications for managing and analysing building elements. BIM enables building elements to be documented with smart parametric reusable objects that contain rich information about the objects use, semantics, topology, relationships with other objects and further information stored as attributes. BIM can be defined as the assembling of parametric objects which represent building components within a virtual environment and which are used to create or represent an entire building.