Table of Contents
Rhino Bezier surface file as written with the OpenNurbs library. Rhino can be used to write surface files which can be read by most CAD programs.
VSP uses its own file format for airfoil points. Some example airfoil files are included in the 'airfoils' directory of the distribution. The example file representing a NACA 23015 is included below.
The file starts out with a simple header. The first line is a file-format identifying header which must contain “AIRFOIL FILE”; otherwise, it is unused by VSP. The second line is the airfoil name which will be displayed in VSP. The third line is a flag to indicate a symmetrical airfoil. The fourth and fifth lines specify the number of points which define the upper and lower surfaces.
The surfaces are given as a series of (x, y) pairs. The top surface first, then the bottom surface. Points are specified from leading edge to trailing edge. There is a blank line between the two sets of points.
Typically, the leading edge will be at (0, 0) and the trailing edge at (1, 0). However, VSP does not check or enforce this. Airfoils with points which extend beyond the x-range of [0, 1] can be used to model high lift systems.
DEMO GEOM AIRFOIL FILE NACA 23015 0 Sym Flag (0 - No, 1 - Yes) 18 Num Pnts Upper 18 Num Pnts Lower 0.0000 0.0000 0.0125 0.0334 0.0250 0.0444 0.0500 0.0589 0.0750 0.0690 0.1000 0.0764 0.1500 0.0852 0.2000 0.0892 0.2500 0.0908 0.3000 0.0905 0.4000 0.0859 0.5000 0.0774 0.6000 0.0661 0.7000 0.0525 0.8000 0.0373 0.9000 0.0204 0.9500 0.0112 1.00000 0.0000 0.0000 -0.0000 0.0125 -0.0154 0.0250 -0.0225 0.0500 -0.0304 0.0750 -0.0361 0.1000 -0.0409 0.1500 -0.0484 0.2000 -0.0541 0.2500 -0.0578 0.3000 -0.0596 0.4000 -0.0592 0.5000 -0.0550 0.6000 -0.0481 0.7000 -0.0391 0.8000 -0.0283 0.9000 -0.0159 0.9500 -0.0090 1.00000 -0.0000
The CAB file can be used to block out components representing cabin decks or other internal components. The file starts with a header specifying the number of decks. Then each deck has a header specifying the number of cabins for that deck. Then each cabin is specified by eight (X Y Z) points which define a block. Each block is separated by a blank line.
NUMBER OF DECKS 2 CABINS 1 0.00000 0.000000 7.500000 75.00000 0.000000 7.500000 64.21629 29.62800 7.500000 0.00000 29.62800 7.500000 0.00000 0.000000 15.00000 75.00000 0.000000 15.00000 64.21629 29.62800 15.00000 0.00000 29.62800 15.00000 CABINS 2 0.00000 0.000000 0.000000 75.00000 0.000000 0.000000 64.21629 29.62800 0.000000 0.00000 29.62800 0.000000 0.00000 0.000000 7.500000 75.00000 0.000000 7.500000 64.21629 29.62800 7.500000 0.00000 29.62800 7.500000 0.00000 29.62800 0.000000 64.21629 29.62800 0.000000 48.77376 72.05600 0.000000 0.00000 72.05600 0.000000 0.00000 29.62800 7.500000 64.21629 29.62800 7.500000 48.77376 72.05600 7.500000 0.00000 72.05600 7.500000
Vorlax case file describing the flight condition and solver parameters to be used for analysis.
When CompGeom is executed, it can produce a wetted area/volume report file in a comma-delimited spreadsheet ready file as CompGeom.csv. This file contains the same information as CompGeom.txt. An example of this file for a simple model is included below. The theoretical areas and volumes are the untrimmed values for each component. The Wetted areas and volumes are the trimmed values for each component.
Name, Theo_Area, Wet_Area, Theo_Vol, Wet_Vol Pod_0,30.309323,28.052179,8.222844,7.930860 Ms_Wing_0,26.345621,20.118482,3.023952,2.406409 Ms_Wing_0,26.345621,20.118482,3.023952,2.406409 Totals,83.000565,68.289142,14.270749,12.743678
When DegenGeom is executed, it can produce a coordinate definitions file of degenerate geometries like the surface, plate, stick and point models as detailed here. Panel and wing camber surface coordinates, panel areas, and similar information are available. This ASCII file can be opened using Excel or editors like Notepad++ and may also be parsed for discretization of geometries in several different physical applications such as Euler-Bernoulli beam theory and vortex lattice solvers. This file contains the same information as DegenGeom.m.
The FEM Meshing part of OpenVSP can write NASTRAN files. These files can then be imported by NASTRAN front-ends like FEMAP from Siemens. They should also be usable directly with NASTRAN itself (for example, as available in this Debian package), though the file will need additional information added into it, to indicate to NASTRAN what forces to apply.
The NASTRAN files consist of a control part at the top, with a bulk data part at the bottom. The bulk data part is made up of lines in free field format, which appears to be simple CSV, but has additional rules placed on it. See https://docs.plm.automation.siemens.com/data_services/resources/nxnastran/11/help/tdoc/en_US/pdf/QRG.pdf, section 9.3.
AutoCAD DXF is a drawing format developed by Autodesk for CAD. The feature lines of a vehicle in VSP form the basis for DXF exports. 3D and 2D representations are available. For a 2D drawing, up to 4 views can be laid out in a single DXF. Additional options are available to add color to layers (identified up by geometry), force feature lines at all cross-sections, and add projection outlines.
Similar to the *.tri file format, a Facet file contains the triangulated mesh data for a surface. Two methods are available for exporting a Facet file from VSP.
- Unintersected components (Comp Geom): File→Export→Xpatch (.facet)
- Intersected components (CFD Mesh): Analysis→CFD Mesh→Output→.facet
File to be used with the Felisa unstructured volume grid generator and flow solver.
VSP uses its own file format for fuselage cross sections. An example cross section file is included in the 'fuselage' directory of the distribution. The example file representing a square box is included below.
The file starts out with a simple header. The first line is a comment field, it is unused by VSP. The second line is the cross section name which will be displayed in VSP. The third line is the number of points in the cross section definition.
After the header, there is a list of (x, y) pairs for the points which define the cross section. Only the positive-x half of the fuselage shape is specified – symmetry is assumed. Points are specified in clockwise order.
VSP will allow you to scale the height and width of a fuselage section defined by the points in the file.
VSP will fit a smooth surface through the specified points. This smoothing can make sharp corners problematic. In the example below, points were clustered near the corners to try to help VSP represent the corners.
FUSE XSEC FILE Box 17 NumPnts 0 1 0.5 1 0.7 1 0.9 1 0.98 0.98 1 0.9 1 0.7 1 0.5 1 0 1 -0.5 1 -0.7 1 -0.9 0.98 -0.98 0.9 -1 0.7 -1 0.5 -1 0 -1
The HRM file is a simple structured wireframe file. It is sometimes referred to as an XSec file or Hermite file. The HRM file contains the wireframe data as seen on-screen.
The HRM file has a header which specifies the number of components at the top of the file. Each component has its own header specifying the component name, type, number of cross sections, and number of points per cross section. Each component is defined by (X Y Z) points for each cross section in order.
In the example file below, many of the points have been omitted for brevity.
HERMITE INPUT FILE NUMBER OF COMPONENTS = 3 Pod_0 GROUP NUMBER = 0 TYPE = 1 CROSS SECTIONS = 11 PTS/CROSS SECTION = 21 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 ..... 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.42400 0.00000 0.31253 0.42400 0.09598 0.29654 ..... 10.00000 0.00000 0.00000 10.00000 0.00000 0.00000 Ms_Wing_0 GROUP NUMBER = 1 TYPE = 0 CROSS SECTIONS = 3 PTS/CROSS SECTION = 21 5.66667 0.00000 0.00000 5.08193 0.00000 0.08031 ..... 7.37429 4.00000 -0.04015 7.66666 4.00000 0.00000 Ms_Wing_0 GROUP NUMBER = 1 TYPE = 0 CROSS SECTIONS = 3 PTS/CROSS SECTION = 21 5.66667 0.00000 0.00000 5.08193 0.00000 0.08031 ..... 7.37429 -4.00000 -0.04015 7.66666 -4.00000 0.00000
OpenVSP relies on the libIGES library for exporting IGES files in accordance with the IGES v5.3 standard. The IGES format is compatible with most CAD packages. The STEP format, which functions as a predecessor to IGES, is also available. IGES exports may be of untrimmed components, trimmed components, untrimmed structural models, or trimmed structural models.
- Untrimmed components: File→Export→Untrimmed IGES (.igs)
- Untrimmed structural models: File→Export→Untrimmed IGES Struct (.igs)
- Trimmed components: Analysis→Surface Intersection→Output→.igs
- Trimmed structural models: Analysis→FEA Mesh→Output→.igs
Vorlax input file.
VSP uses industry standard JPEG files for input and output of images.
The two main uses of JPEG images in VSP are to save a copy of the display window and display a background image on the display window. The background image may be a beautiful sunset or a 3-view drawing to match the model.
Background images can also be displayed when editing a fuselage cross section. Finally, JPEG images can be used as textures applied to the surface of the model.
When DegenGeom is executed, it can produce a coordinate definitions file of degenerate geometries like the surface, plate, stick and point models as detailed here. This file can be opened using Matlab or GNU Octave and may be used for discretization of geometries in several different physical applications such as Euler-Bernoulli beam theory and vortex lattice solvers. Panel and wing camber surface coordinates, panel areas, and similar information are available in a structure array data type named
degenGeom. This file contains the same information as DegenGeom.csv.
An example of Unnamed_DegenGeom.m file executed in Octave is included below.
octave:1> Unnamed_DegenGeom octave:2> degenGeom degenGeom = 1x2 struct array containing the fields: type name geom_id surf_index main_surf_index sym_copy_index flip_normal transmat surf plate stick point octave:3> size(degenGeom(1).surf.x) % Size of array containing x-coordinates of surfaces in Component 1 ans = 6 33
Gmsh is an open source mesh generator. VSP surface triangulations may be written to MSH format to be read by Gmsh.
NASCART-GT is a Cartesian unstructured Navier Stokes CFD code. VSP can work with NASCART bodyin.dat geometry files.
Wavefront object file. VSP can sore a triangulated surface in a an OBJ file. Only vertex 'v' and face 'f' data is output.
VSP can output a surface mesh in a format appropriate for the TetGen volume mesher. This file is output in TetGen's own POLY format.
VSP's own trimmed surface file format. This file approaches all of the information required for a formal BREP representation of a geometry.
ASCII stereolithography file for triangulated surfaces. The lingua-franca of triangulated surfaces. Although they are rather limited, almost everything can work with STL files.
The STL file format cannot identify which component each triangle is associated with. Consequently, the STL file format can only represent a single watertight surface.
There is a non-standard extension to STL which includes several solids in a single STL file, each with it's own name. Some STL readers can use this metadata in order to use the different solids. During STL export, choose the “Tagged Multi Solid File (non standard)” option.
STL files do not natively store connectivity between triangles. Since many programs need this connectivity information, they must re-build the connectivity by checking point proximity. For some models, this process can introduce topological problems with the model.
STL files contain a large amount of redundant information. Consequently, they can be very large for a given model – as much as six times the size of other ASCII formats. A binary version of STL exists, but OpenVSP only writes the ASCII version.
A useful tool to inspect and edit STL files and convert them to binary if needed is https://www.meshlab.net/.
OpenVSP uses the STEPcode library to export Part 21 exchange files for interfacing with CAD programs. Alternatively, the IGES is also available for exporting to CAD. OpenVSP supports STEP export of untrimmed components, trimmed components, untrimmed structural models, and trimmed structural models.
- Untrimmed components: File→Export→Untrimmed STEP (.stp)
- Untrimmed structural models: File→Export→Untrimmed STEP Struct (.stp)
- Trimmed components: Analysis→Surface Intersection→Output→.stp
- Trimmed structural models: Analysis→FEA Mesh→Output→.stp
SVG, or Scalable Vector Graphics, is an XML-based 2D vector representation of an image. In VSP, an SVG drawing of a vehicle can be exported, which can then be opened using any web browser. Similar to DXF export, options are available to force feature lines at all cross-sections or add projection outlines. Up to four views are supported for an SVG export.
VSP can use TARGA image files as textures applied to the models. TGA files support transparency, which can be very handy when making non-repeating textures.
Cart3D surface triangulation format. TRI files are documented here.
VSP can output three kinds of triangulated surfaces to Cart3D.
- Unintersected components (Configuration)
- Intersected components (Wetted Surface)
- Isotropic surface mesh (Wetted Surface)
When CompGeom is executed, it can produce a drag buildup report file as a tab-delimited file as DragBuild.tsv. An example of this file for a simple model is included below.
In addition to the theoretical and wetted area and volume data included in the other CompGeom reports, the DragBuild.tsv file also includes other information such as thickness-to-chord ratios and fineness ratios which are commonly used in a drag buildup.
Name Theo_Area Wet_Area Theo_Vol Wet_Vol Min_Chord Ave_Chord Max_Chord Min_TC_Ratio Avg_TC_Ratio Max_TC_Ratio Ave_Sweep Length Max_Xsec_Area Len_Dia_Ratio Pod_0 30.309323 28.052179 8.222844 7.930860 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 Ms_Wing_0 26.345621 20.118482 3.023952 2.406409 1.999990 2.999995 4.000000 0.120000 0.120000 0.120000 44.999980 0.000000 0.000000 0.000000 Ms_Wing_0 26.345621 20.118482 3.023952 2.406409 1.999990 2.999995 4.000000 0.120000 0.120000 0.120000 44.999980 0.000000 0.000000 0.000000
Note: in this example the tab characters have been replaced with three spaces to facilitate proper display in various browsers.
When CompGeom is executed, it can produce a wetted area/volume report file as CompGeom.txt. This file contains the same information as CompGeom.csv. An example of this file for a simple model is included below. The theoretical areas and volumes are the untrimmed values for each component. The Wetted areas and volumes are the trimmed values for each component.
...Comp Geom... 3 Num Comps 3 Total Num Meshes 664 Total Num Tris Theo_Area Wet_Area Theo_Vol Wet_Vol Name 30.309 28.052 8.223 7.931 Pod_0 26.346 20.118 3.024 2.406 Ms_Wing_0 26.346 20.118 3.024 2.406 Ms_Wing_0 ------------------------------------------------- 83.001 68.289 14.271 12.744 Totals
- Automation script (txt)
- Wetted area/volume report (txt, csv)
- Area ruling report (txt)
- Mass properties report (txt)
Native VSP parametric geometry definition. The VSP file is saved in XML format and can be relatively easily read, parsed, and updated.
Model for 3D web. X3D is an XML successor to VRML.