The untrimmed CAD export types (STEP/IGES) produce a standardized CAD file built from the native OpenVSP Bezier surfaces in the model. The surface resolution displayed in the workspace defined by Num U, Num W, clustering, etc. has no effect on the resulting CAD files. Once you have chosen a set of components and a format type, the Untrimmed STEP/IGES Options menu will appear. In this window, the desired length units must be defined along with a tolerance (accuracy) for the export. Multiple other options are available enabling users to tailor the export format toward their CAD program of choice. For example, some programs will import the model with gaps or breaks in wing trailing edges or fail to accept non-split surfaces. In these cases, options are provided to address these issues.
Unfortunately, the rules defining the STEP/IGES format are relatively loose and were defined by committee. This means that writing a STEP or IGES file is much easier than reading one. If your CAD program has issues reading an OpenVSP CAD export, try different options to see if you have some success. It may also help to write a STEP/IGES from the CAD program and compare or to research what specific style of STEP/IGES that CAD program expects.
An OpenVSP model may be exported as a triangulated mesh such as an STL, TRI, OBJ, etc. For each of these formats, the resolution of the exported mesh will directly reflect the resolution of the OpenVSP tessellation shown in the workspace (Num U, Num W, clustering, etc.). Triangulated mesh formats will typically export as a single mesh or multi-solid mesh as appropriate for each type without providing the user an option. However, STL exports may be set up to write either a single mesh or a tagged multi-solid file. STL formats also have the option of exporting Prop components at the origin rather than in their set location in the model. This is useful when you wish to export a mesh of an isolated rotor at the origin without having to move it in the model.
An OpenVSP model may be exported in a wide variety of formats including triangulated meshes, rectilinear wireframes, standardized CAD, vector drawings, blade element, and airfoils, among others. Each of these file types will require their own options and model setup to achieve a quality export which will be discussed in subsequent topics along with reasonable best-practices. The Export menu is located in the File menu. Similar to Comp Geom, users may select different components for the Normal (thick-surface) set and the Degen (thin, camber surface) set.
Blade element momentum (BEM) models may be imported to OpenVSP as Prop components in which each of the BEM stations are set as Prop blade control points. Because the Prop component is perhaps the most complex geometry in OpenVSP, it can take quite a while to update models with excessive numbers of control points when in Blades mode. This tends to happen when imported BEM models can have 20+ stations. A way to alleviate this is to switch the Prop to Disk mode, which doesn’t require a visual update to loft the blade with each parameter change. Users may also wish to convert the blade control curves to Approximate Cubic Bezier to reduce the number of points. This can be quickly accomplished for all blade curves by clicking “Approximate All” under the Blade tab.
For more information about working with Prop components, refer to the Propellers subject and topics.
Point clouds may be imported into an OpenVSP model from the Import… menu. The point cloud (PTS) format is a very simple X Y Z triad with each row corresponding to a new point, which makes these files very easy to read and write. Once imported, the point cloud may be used as a visual target for manual modeling or as Fit Model targets.
