Import Tab Functions
Time to read: ~8 min
The Import tab is the first tab page shown on starting the application (default tabs show Import,
For all practical purpose, the process by which the application is intended to be used is to start on the left tab (Import) and work
through the tabs to the right until the data is Exported. Some or all of the tabs in between may be skipped if they are not required.
In some cases, the data does not need correcting or editing, thus the Edit and Repair tabs may be ignored. Similarly, if the data consists
of only a single Body, the Bodies tab may be ignored as the data does not need to consider multiple bodies (though perhaps modifying it?).
If the exported data is to consist of Triangular features (equal to the data being loaded), the Features tab can also be skipped.
The Reverse Engineering Tab is a good tool to use for cases where sketch data is to be obtained or organic shapes converted to NURBS Surfaces.
The options provided on the Import tab should be considered to be immediately related to the process of importing data from the
supported file formats:
File Types supported
The InStep application is primarily concerned with loading data from mesh files. The primary import file format is the STL (Stereolithography) file type. Both
Binary and Ascii (plain text) formats are supported with automatic detection of which type a STL file is saved in. In addition, Alias Wavefront Object (OBJ)
files are supported too, though their formatting can be more complicated as they can define things such as materials (colors, texture, etc.) which is of little
interest in the final data to be converted. At this time, it is expected that OBJ files from all common export tools can be read and the data extracted that is
of interest to the InStep application. Nevertheless, if there is too much information that is of a non-standard format, it may confuse the import tool
and might cause unexpected behavior.
One item that has frequently been requested is the support for other, perhaps more exotic, formats. As the InStep application is primarily concerned with the
conversion of mesh data to boundary representation (BRep), support for files such as VRML has not been a major focus though the application supports
PLY, OFF and 3DS in addition.
Beyond the usual polygon files, the application also supports point data in the .XYZ file format. As it is possible to include both point and point-normal data, the
application will check the contents and alert the user if the data does not contain normals for the point data. Normal Vectors (aka. Normals) at each location are
important as they define which side of the surface is inside and which is outside. InStep provides a few tools for generating normals, but, as this is not the focus
of the application, incomplete meshing may result from this. It is always recommended that Normals are obtained from the 3D scanner and maintained in the files.
For use with Computer Aided Engineering applications, the import also allows Finite Element formats to be imported. If such a format is detected, the application will
further provide access to the Elements tab where a number of tools can aid in the conversion of data.
More information on the import of Polygon data can be found on the Import: Polygon page
Generally, none of the polygon (STL, OBJ, ...) file formats define the units that are applicable to the values provided in the file. Therefore, it sometimes becomes necessary
to scale the data in order to make sense of the values. The most frequent scenarios are those where the user usually works in units of Inches (in the USA) or Meters
(most of the rest of the world) but the data was stored in the file assuming units of Milli-Meters (or Inches or something else). Therefore, when the data is loaded, the scale or
overall size seems either very big or very small.
For this reason, it is frequently necessary to re-size or scale the data to better represent the actual data being used. Though it is perfectly reasonable to simply
keep the units as a one-to-one ratio by setting the import and work units both to the same units (likely Milli-Meters: 'mm'), it sometimes makes more sense
to define what the import units are and what the desired work-units are and thereby using a true representation of the data.
What is important to keep in mind is that the application uses a limited number of digits when working with the data ('Single' or 'Float' to be specific, which means that
the data is stored in a format that holds a limited number of digits together with an exponent; see
Single-precision floating-point format for more information). Some calculations do use more precision,
but by applying a very large or very small scale, the data can become collapsed in some locations.
As mentioned above, working with files that do not specifically define the units that were used, the resultant shapes can look very large or very small. For this reason, it is often
desirable to 'correct' for this by specifying the units expected of the data being loaded and the units to use for working with the data.
The Resize button, located on the Import tab brings up a tool that allows the units for the imported data to be defined together with the units
that the user wishes to use going forward. Both units are then stored as the defaults (if the 'Save' option is selected) going forward for new data being read and written. The
work units in particular, are also stored in the STEP file (if that is the file ultimately written to) and therefore passed on to other applications.
The following options are available on the Resize tool menu:
Work Units: Sets the units to be used for export and display purposes
Lower Corner: Indicates the lowest sets of coordinate values found, essentially representing the lower bounds of a box that the data fits in.
Upper Corner: Indicates the highest values found.
Size: represents the lengths of the sides of the box defined by the Lower and Upper Corners
Loaded Data is in Allows selection of what units the original data was in. The values for the bounding box & size update according to what the Work units were set to and what units were selected.
Make this the default: if checked, means that the settings are updated to use these settings as the default for future data import.
Scale: This value shows the scale being applied to the data based on the selections above. In the unlikely event that the choices are not correct or a non-standard scaling is desirable, the scale can be set manually. Note that the work units will remain what they were set to so manually entering the Scale is usually not necessary.
The Preview button allows the data to be temporarily altered while the Apply button makes the scale permanent. Cancel causes the changes to be ignored. Both Apply and Cancel close the dialog box.
Clicking the Info button brings up a dialog box with basic information about the data that has been loaded. Specifically:
- Total Number of Bodies
- If more than one body has been imported (or obtained from a Split operation), the number of bodies are displayed
- Total Number of Features
- If multiple bodies are present, the total number of features are defined. Features are considered geometric shapes that we ultimately be exported to the STEP file.
- Global Bounding Box
- If multiple bodies, this range of coordinates will define the extent of all data; this is the smallest box that is aligned with the coordinate axes that can hold all data loaded.
- Body *
- For individual bodies (if multiple) or single body (if only one or not yet split) this will define the ID of the body and any names associated with it (depending on the file format).
- Indicates the color value (represented as an ARGB value in hexadecimal notation).
- Shows the total number of features for the body. Each feature represents a boundary entity to be exported (if in the STEP format).
- The geometric center (barycenter) of the data for this body. The center is merely the half-way point between the bounding box extents.
- Provides information about the extent of the data along the X,Y and Z coordinates in the selected units.
The Clear button does exactly as indicated: it clears all data from the memory. This function is usually not required as importing data will automatically erase all prior data. Note that this function cannot be un-done.
Once the data is cleared, it is removed from the application's working memory. Any underlying files are not affected.
It is possible to combine multiple files into one by using the Insert option to add additional files once a first file has been imported. Note that this approach is contrary to
the recommended option of working with one shape at a time. Other applications may be better suited for working with bodies and adding/removing/transforming them.
The option exists to take a regular STL mesh or similar and to convert it to a Finite Element format for use in Numerical Analysis tools or similar. The option to convert
to FE simply modifies the data internally to make the additional tools available and to export the results to a CAE related mesh format.