# File formats

### 3dm

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.

### af

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

### cab

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

### Calculix

Open source Calculix FEA program. Calculix files are identical in format to those used by ABAQUS.

### cas

Vorlax case file describing the flight condition and solver parameters to be used for analysis.

### csv

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

### fel

File to be used with the Felisa unstructured volume grid generator and flow solver.

### fxs

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

### hrm

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   

### inp

Vorlax input file.

### jpg

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.

### msh

Gmsh is an open source mesh generator. VSP surface triangulations may be written to MSH format to be read by Gmsh.

### NASCART

NASCART-GT is a Cartesian unstructured Navier Stokes CFD code. VSP can work with NASCART bodyin.dat geometry files.

### obj

Wavefront object file. VSP can sore a triangulated surface in a an OBJ file. Only vertex 'v' and face 'f' data is output.

### poly

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.

### srf

VSP's own trimmed surface file format. This file approaches all of the information required for a formal BREP representation of a geometry.

### stl

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 can not identify which component each triangle is associated with. Consequently, the STL file format can only represent a single watertight surface.

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.

### tga

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.

### tri

Cart3D surface triangulation format. TRI files are documented here.

VSP can output three kinds of triangulated surfaces to Cart3D.

1. Unintersected components (Configuration)
2. Intersected components (Wetted Surface)
3. Isotropic surface mesh (Wetted Surface)

### tsv

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.

### txt

##### CompGeom.txt

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)

### vsp

Native VSP parametric geometry definition. The VSP file is saved in XML format and can be relatively easily read, parsed, and updated.

### x3d

Model for 3D web. X3D is an XML successor to VRML.