Build a Two Part Mold

In this tutorial we will build a two part mold of a high-rise building massing model for casting. The key point of interest is performing Brep/Solid Boolean operations, unions, subtraction, splitting, using programming, to create complex solid models.



  1. Create a solid mold block by creating and converting a generic axis aligned bounding box into a solid.
  2. Create (or import) one or more solids that represent the building’s massing model and Boolean union multiple solids into one mass (optional).
  3. Create cylindrical registration dowels that run across the mold block perpendicular to the slicing direction.
  4. Subtract the massing model, one or more parts, and registration dowels from the mold solid.
  5. Split the mold block into two parts and emit the two volumes.




  1. This approach to generating massing models is not quite useful unless the design concept/scheme is very clear.
  2. Boolean operations are rather slow, take significant computing power and don’t run in fluid parametric sketching mode. They are rather fragile, prone to numerical errors, topological changes and generally failures.
  3. In conclusion, operating on solid models with Boolean operations is rather counter-intuitive via code. Perhaps applications such as Solidworks/CATIA etc are more appropriate for this kind of modeling process.