You can import geometry from external CAD formats into a mass instance or mass family in the same way that you import such geometry into other family definitions. However, in some cases, imported geometry is not well suited to mass instances.
When imported geometry is not well suited to mass instances, it may be possible to use the generic model category instead. There is overlap between the mass instance and generic model categories. Walls, roofs, and curtain systems can be made from faces in a generic model family. Floors can be created from sketches that reference the geometry in a generic model or a mass model. Mass models also support level-based mass floors, which in turn support one-click parametric floor creation.
When using imported geometry in mass families and generic model families, consider the following:
- Avoid complex geometry in mass instances. Unlike other family categories, mass instances always maintain a separate copy of each internal geometry, plus extra geometry to represent the combined volume of the mass. For complex geometry, the additional data can slow down processing considerably. When a generic model is joined by the Join Geometry tool, the software also creates an extra copy of the geometry, which can slow performance. For complex geometry in a generic model, you may join the geometry inside a family definition to avoid extra copies of the geometry.
- If the imported geometry in a mass instance (or between generic models) is not well suited to join geometry, then errors, warnings, and unexpected behavior can result. If geometry is combined within a mass definition, it should be solid geometry with either a strong connection or no connection. Examples of geometric characteristics that are ill-suited to joining include odd tangencies, edge-only overlaps, open meshes, and ambiguous connectivity.
- Some CAD formats do not have geometry in a form that a mass instance can use to compute volumetric information and mass floors. When such formats are used, errors and warnings result. For more information about imported CAD formats, see Suitability of Imported Geometry.
- Host by Face tools (available for roofs, floors, walls, and curtain systems) associate a single host element with one face or several faces. For example, detailed geometry (that contains cornices, reveals, windows, casework, tessellated approximations of surfaces, and so on) is likely to have many small faces that will fail to produce meaningful host elements and may produce errors. This is a consideration for both mass families and generic model families.