vrml2nav

The vrml2nav program is a utility to generate mesh and geometry information in the scene description file format from a scene given in the VRML 1.0 format^6.1. After installation of the NaSt3DGP-package it can be found in the bin directory of the installation path(where also navsetup and navcalc reside).

The usage is very simple, just type

vrml2nav $\langle$vrmlfile.wrl$\rangle$

where $\langle$vrmlfile.wrl$\rangle$ is the file containing the description of the scene in VRML 1.0 format. In addition, vrml2nav reads the textfile vrml2nav.cfg. In this file you just need one line to specify where the output (the scene description in nav-format) should be written. The line begins with the keyword outputnav followed by a filename, i.e.

outputnav $\langle$outfile.nav$\rangle$

This procedure generates a scene description file which can be processed with navsetup as described in chapter  to generate an input file for the calculation. The vrml2nav utility writes some default values for the different parameters like Reynolds-number etc. in the nav-file. These parameters as well as the grid resolution should be adjusted according to the calculation to be done. The nav-file generated by vrml2nav can be edited with any text-editor and all parameter settings explained in section  can be used. The poly-blocks in the scene description represent the actual geometry given in the VRML 1.0 file.

Figure: Snapshot of a Porsche model, VRML 1.0 scene (top), Tecplot visualization of flag field(bottom)

Figure: Snapshot of a submarine model, VRML 1.0 scene (left), Tecplot visualization of flag field(right)

In figures  and  two examples are given. On the left a screenshot of the original VRML 1.0 description is shown, on the right side a visualization of the corresponding translation into the nav-format is shown. The visualization was done with Tecplot in the following way: first the binary data file was generated with navsetup, then, also with navsetup, output for Tecplot was generated (see chapter ) and within Tecplot the isovalue 1.0 of the variable flg (which stands for flag field) is visualized. For the Porsche, a mesh resolution of 180 cells in $x$-direction, 90 cells in $y$-direction and 120 cells in $z$-direction was used, the mesh for the submarine has 128 cells in $x$-direction and 32 cells in $y$- and $z$-direction.

Note that very thin features (for example, like the antenna of the Porsche car are translated by the vrml2nav converter, but can of course only be represented in the binary data file if the mesh resolution is fine enough.