Teigha BIM: Faceted Topologies

There are several types of faceted topology objects in Teigha BIM. Each type has four different parameters:

• Max points
• Precision
• Presence of offset
• Flags

The following is a table of facet topology differences:

As you can see, there are pros and cons to these types of facet topologies:

• Max Points — A container for faceted topologies with 4M points occupies more memory, but it can represent a more detailed model (up to 4 million points can be used).
• Precision — A container with double precision values (“double”) is more precise but takes two times the memory than single-precision (“float”): 8 bytes instead of 4 bytes for each point.
• Offset — An additional 3D-based value allows for the possibility to add the object’s offset, but it allocates more memory.
• Edges visibility flags — More memory is needed for these flags, but it gives additional advantages in special cases.

To create various faceted topologies, the Teigha BIM “BmMasterImportSymbolGPolyMesh_20009_ISH“ test was created (you can find it in \Bim\Tests\TB_UnitTests\BmMasterImportSymbolGPolyMesh_20009.cpp). It demonstrates the creation of different faceted topologies, including import from an .stl file.