File Filters
Using the filters (i.e. changing the extension) in the Save As dialog box is how different file formats (and their capabilities) are selected.
The InStep Studio application has internally only five formats it targets: Binary and Ascii (plain text) STL files, OBJ files, STEP (or STP) files, (stanford) PLY and Object File Format (OFF) formats.
The inclusion of STL and OBJ are merely there to provide a way to export data once it has been modified in a way that allows updates exterior to the
application. Feature detection applied during a different stage of the process is not applicable to formats other than STEP. With the STEP format
(officially ISO 10303 AP 214) surfaces of higher complexity are defined by their boundaries, hence the term Boundary Representation. Underlying perimeter
information such as edge loops, oriented edges, etc. are obtained from the data and automatically generated.
File Size
One item that may require some elaboration is the size of the resultant files. It is often, though incorrectly, assumed that the size (on
disk) of a file is in relation to the file ultimately generated. Though there is some relationship, there are several items to consider.
For one, binary STL files can be orders of magnitude smaller than Ascii STL files while defining exactly the same information. It would be
incorrect to use one or the other without also knowing what type they are. Further, as STL files can easily contain incorrect or unused information
such content may artificially 'bloat' the file.
OBJ files contain a more robust system in that locations are defined and then references to them are used for definition of faces. However, even here
there can be additional bloat in that vertex normals (or texture coordinates) may be additionally defined which are not used by the application.
Edges (defined by two points) are ignored by the application during load time as they are explicitly generated for each triplet of corner points.
During export to the STEP format, a large number of additional items are generated which are required by the format to define edges, orientations, normals,
directions and similar. All entities written in a plain-text format further increasing the file size (but allowing files to be highly compressible
to a ZIP or other compressed formats). Though there is a more compact form of the STEP file (using abbreviated or short entity names), such format is usually
not well supported and thus not being used here.
The best way to keep files compact is to keep a close eye on the number of facets and to re-create Features wherever possible. If the original number
of faces is too high (depending on the final use anything above 10,000 faces or less may be considered problematic), the Expert interface provides tools
to allow systematic and targeted reduction of the underlying data whilst retaining the overall definition of the Topology.