(n). Geometry that is a copied representation from outside of the model.
In this article:
Before diving into the nuances of copy geometry, we must first understand the different types of geometry that can be used in skeleton models. As mentioned in “The Basics of Skeleton Models,” skeleton models have datum and surface features. These features are either direct references or copy geometry.
For reference as you read this article, a .PRT signifies a part in Creo, while .ASM signifies an assembly.
Direct References vs. Copy Geometry
Every Creo model has a default coordinate system that is the origin of all other direct references in the model. In other words, direct references refer to the default coordinate system and must be created inside a skeleton model. Copy geometry does not reference the default coordinate system in the model; instead, it is created from external models.
For example, consider the 3-shelf skeleton on the right. If we simplify the model to only show SHELF_1, we see that it is defined relative to the DEFAULT_Y plane (i.e. the default geometry). As shown from the picture, SHELF_1 is represented as a specific distance of 16 inches from DEFAULT_Y.
Copy geometry are features that are copied from outside (external) models. In other words, only the surfaces, datums, and other selected features from the outside model are copied. References are always made to the original “outside” model. This helps with geometry placement updates, but those references can be broken in the case of an external copy geometry. For more information on this concept, read “Working with External References.”
For example, on the right, the box of this model, COPYGEOM_BOX is copy geometry because it copies the geometry of BOX1.PRT that lives in the completely separate SHELF_1_EQUIP.ASM assembly. COPYGEOM_BOX references surface features from BOX1.PRT. If BOX1.PRT were to move inside SHELF_1_EQUIP.ASM, the COPYGEOM_BOX will update with it.
Stay tuned for additional blog posts on the difference between local and external copy geometry, as well as the pitfalls of shrinkwraps. In the meantime, if you’d like a deeper dive, see this prior blog post on skeleton models.