Component:Cellular Topology
From DocR21
The Cellular Topology Component (CT) allows modeling of subregions in a solid. For instance, to represent a solid made up of two different materials laminated together, you could use cells with different material properties attached to them. These cells can be either 2D sheets or 3D solids. The benefit of this is that unique information can be associated with each cell. In finite element and finite difference analysis (for example, used to analyze stress, temperature, and magnetic fields), a model is subdivided into a number of geometrically simple regions for the purpose of simplifying the calculations. Cells can be used to represent this type of subdivision, too.
| Operation | Description |
|---|---|
| Adding cellular topology | Adds c-faces to the appropriate sides of all faces and aggregates the c-faces into c-shells and cells. The APIs are api_ct_attach_cells and api_ct_attach. |
| Querying mass or area properties | Computes the area of a CELL or the mass properties (volume, center of gravity or moments of inertia) of a CELL3D. The APIs are api_ct_cell_area and api_ct_cell_mass_pr. |
| Querying the topology of a cell | Determines the FACEs, EDGEs or VERTEXes of a cell and returns them in an ENTITY_LIST. The APIs are api_get_faces_from_all_entities, api_get_edges_from_all_entities and api_get_vertices_from_all_entities. |
| Copying the cell | Copies the cell to a single separate BODY. The original BODY is not modified. The API is api_ct_copy_cell. |
| Determining point containment in a cell | Determines whether a given point lies inside, outside, or on the boundary of a 3D cell. The API is api_ct_point_in_cell. |
| Checking | Automatically carried out by the checker but also available directly via the API api_check_ct. |
CT is merely a data structure on top of the ACIS topological structure. It is very general, very flexible, and low-level. This auxiliary data structure organizes models with mixed dimensionality into the solid and sheet cells from which they are composed. A single lump can potentially contain many solid and sheet regions. CT computes, maintains, and edits a secondary representation, attached through attributes, that stores all solid and sheet cells, as well as the "face uses" that comprise them. This data may be attached to or removed from any lump at any time.
Lumps are defined as connected regions of mixed dimensionality. Shells are defined as connected face sets, for example:
- A 2D sheet is a single lump and shell.
- A solid, decomposed into many smaller solids by internal double-sided faces, all of which are interconnected, is a single lump and shell.
- A solid containing a disconnected, embedded set of faces, consists of two shells.
- A body consisting of a block and a disconnected, non-embedded sheet (double-sided, both-outside) face is represented by two lumps.
Note, however, that cellular topology cannot be attached to a body containing an incomplete shell. A consequence of this is that an operation on a body, which would result in an incomplete body, will fail if the body has cellular topology attached. (Refer to Automatic Recompute for details on how to control this behavior.
