Parametric modelling

Parametric modelling is a design method in which geometry is described by parameters and relationships rather than by fixed, manually drawn shapes. A wall is defined as a curve, a thickness, a height and a rule for how the surface varies, so adjusting any input regenerates the whole model. Common tools include Grasshopper for Rhino, Dynamo for Revit, and scripted modelling in Python or C sharp.

In practice

Parametric models matter in printing because the same definition can carry the design constraints and the machine constraints at once. Layer height, nozzle width, minimum radius and maximum overhang angle can be parameters in the model, so a geometry that the printer cannot execute never reaches the machine. In many 3DCP workflows the toolpath is generated in the same definition that produced the form, which avoids exporting a solid and slicing it afterwards. The cost is that a parametric definition is effectively a small piece of software: it needs naming discipline, documentation and version control, or it becomes unmaintainable once its author moves on.

Related terms

• Toolpath — the machine path a parametric definition often produces directly.
• Slicing — the alternative route, cutting a finished solid into layers.
• BIM — the coordinated building model a parametric design usually has to fit into.