CAD, PLM Models in STEP, IGES may be imported and converted using the OC interface, based on the OpenCASCADE core library. Various settings to adjust the conversion process are available on this interface sub-panel.
Linear deflection provides an additional limit imposed on the boundary representation algorithm, which controls the distance between the original curves in the geometry and the newly generated mesh.
Lower limits on deflection values will result in a finer mesh whilst higher limits on deflection will result in a coarser mesh.
If the limit of linear deflection is defined as less than shape tolerance (computed through other user-defined constraints on meshing), the meshing algorithm is driven by the triangle size tolerance and linear deflection will be unable to provide a finer mesh.
There are two methods used to define deflection values, absolute and relative (default).
Absolute deflection is a specific value, defined in the interface, which corresponds to the units used in the imported CAD file. Absolute deflection sees the same value used for each tessellation.
Relative deflection is used as an alternative to absolute deflection which allows for more detail in complicated parts of the geometry. This calculates a linear deflection value based on an inputted scale factor which is then multiplied by the diagonal length of the local shape bounding box.
This bounding box is based on the entity shape (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax) for the face being meshed (angular deflection is fixed at 0.5 radians).
The process of boundary representation results in a mesh of triangles which, in fitting the original geometry, may be varied in size (with larger triangles on faces of simpler geometry).
For applications in which more fragmentation is desirable, the feature of subdivision may be introduced. Subdivision is an additional processing step, independent of deflection, performed on each face separately.
Subdivision imposes an upper limit on the lengths of triangle edges. It is inputted as a scale factor which is then multiplied by the diagonal length of the local bounding box for the individual face (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax) being subdivided.
Users should note that subdivision is sensitive (the number of triangles follows an inverse square relationship), meaning small changes may drastically increase the number of triangles and file size.