To create the 3D model add the command export model to the configuration file. For example, "export model -fmt therion". The native format of therion is the one used by the viewer (in xtherion). You can also export the model in other formats:

• "loch", therion native format, ".lox";
• "compass", ".plt" file;
• "survex", ".3d" file;
• "dxf", AutoCad DXF (Drawing Interchange Format) file;
• "esri", ESRI shape files;
• "vrml", Virtual Reality Modeling Language;
• "3dmf", Quicktime 3D metafile;
• "kml", Google Earth file.

After compiling you get a file with extension ".lox". If you do not specify the "-output" option, the default name is "cave.lox". This file can be viewed with xtherion.

When you export the model in DXF (default name "cave.dxf"), the model is very simple. It contains only three "layer"s: the centerline (CENTERLINE), a triangulation of the walls (WALLS), and the enclosing bounding parallelogram (BBOX). All the symbols and texts that compose the drawing are not exported.

The model is generated from the contour of the map, ie, the outlines of the scraps. The height of the passages is computed taking into account points of type "passage-height" and points of type "dimension", which specify the dimensions of the cave passage in directions perpendicular to the page [thbook 36, thwiki 2]. For instance "point dimension -value 4.0 2.0 m" specifies a point where the passage ceiling is four meters above the centerline and the floor is two meters below [thbook 21]. The units is optional. Only plan scraps are taken into account when generating 3D model.

When you export a model you can specify which cave items to include,

• cave-centerline
• centerline
• walls
• surface
• surface-centerline

You omit the items of a class with the export option -disable followed by the item name. For example, -disable walls. You add the items of a class with the option -enable followed by the item name.

For the walls you can tell therion whether to use the survey LRUD data (centerline), the scrap data (maps), or both (all) which is the default. For example (another option of export), -wall-source maps. Naturally, if you specify the maps, and do not have any map file, there will be no walls in the exported model. If you specify -wall-source all the model contains both the tubes of LRUD data (if present) and map data (if present). Therefore if you have maps and LRUD you should choose one or the other.

Since version 0.4.0 (sept. 2006) therion uses the 3d viewer "Loch" and exports 3d models in "loch" format by default. Therefore the "export model" command implies "-fmt loch -output cave.lox". To create 3d model in the old "thom" format you must specify "-fmt xtherion" or provide an output filename with extension ".thm".

If a surface grid is provided, the exported model contains also the surface, with the cave shown in transparency underneath. The entrance of the cave should be "fixed" properly accordingly to the grid. In the following example the cave entrance (first station of the firat survey) has fixed coordinates, and the surface is described both as bitmap and a grid. The bitmap file can be either PNG or JPEG. The grid data are contained in an external file which is included with the input command.

   centerline 
     date 2007.04.19
     cs ESRI:26591
     fix 1@no_01 1482226 5077758 619
   endcenterline
   surface
     cs ESRI:26591
     bitmap ortofoto2.jpg [0 457 1481724 5077991 589 0 1482821 5077139]
     input grid.out
   endsurface

For the moment the cs command must come before the fix command, otherwise Therion fails to apply the magnetic declination.

The grid defines the surface elevation; the bitmap provides the surface texture. If the bitmap is not specified the surface is left grey. For the moment loch on Linux does not handle the bitmap texture.

The 3d viewer loch requires wxWindows and vtk. It is contained in the subdirectory "loch" of "therion". The executable is independent from xtherion and not is integrated into that. To display the 3D model you must execute the loch program and load the file cave.lox (or whatever you named it).

The loch display of the cave 3d model and the surface handles nicely the transparency, so that one gets an idea of what is behind.

The cave coloring by the altitude is also a useful hint to understand where a cave passage lies. If you have specified the geographical coordinates for at least one station (with the fix command) the color legend has the altitudes. Otherwise it has the depth relative to the cave entrance.

With loch you can

• choose the point of view ("Tools | Camera"). You can select the "orientation" (pan and tilt angles), the "focus", and the speed of rotation. Or you can enter the coordinates (East North and altitude) of the camera. Finally you can get a double colour display for a stereo view (you need two-color glasses).
• open a file (menu "File | Open") and save screenshots ("File | Render to file")
• move the display, either with the menu "View | Action", or with the mouse buttons (left button to scale and rotate, right button to shift);
• choose the item to display among centerline, walls, surface, bounding box and the indicators ("Tools | Scene | Visibility");
• choose whether to colour by the altitude as RGB or grey ("Tools | Scene | Color mode");
• define the transparency of the walls ("Tools | Scene | Walls") and that of the surface ("Tools | Scene | Surface");
• make the scene rotate ("View | Rotation");
• select the orientation ("View | Orientation") among plan, profile, east, north, west and south, or display an orthogonal projection ("View | Orthogonal").

To export the cave survey data as dxf file you must use the option -format dxf in the export command.

The DXF file can be visualized with dxfviewer, which is written in java. The DXF file contains layers for the centerline (light blue), the walls (black), the surface (green), and the bounding box (red). The figure below shows the difference between thw walls from the map (on the left) and those from the LRUD data of the centerline (on the right).

Therion can export the output in ESRI shape file format . The shape files can be imported and visualized in any GIS (geographical information system) software, such as GRASS and QGis . A brief introduction to GRASS, by T. Gonon, is included in the Therion wiki.

To export the survey as shape file you need the export command with format esri (or shapefile, shapefiles, shp):

   export model -fmt esri -output cave.esri

This results in a directory, named cave.esri, with the shape files (extension shp), the database files (extension dbf, for dBASE), and the shx files (shape entities file associated with AutoCAD and with ArcView).

To visualize it in GRASS, you must

• import the vector data using OGR (File | Import | Vector map) Select the files "shots3d.shp", "stations3D.shp" and "walls3d.shp", in turn. Enter a name (in the grass environment) for each, and check the 3D checkbox.
• start a display: "Displays | Start display | X0"
• set the region size to the data: "GIS | Region | Manage region" Select "Set the region to match this vector map" and choose one of yours names.
• display the vector data "Display | Display vector map". Choose an input vector data as "Name of input vector"
• Refresh the display "Display | Redraw active display"

With QGis things are much easier. Open a new project (menu "File | New project") and add a vector layer (menu "Layer | Add vector layer"): choose one of your shp files, Repeat for the others. You can also add a georeferenced map (raster layer) to see the cave overlay.

To export the cave survey data in the format used by Google Earth, you specify the "kml" format, or an output with ".kml" extension. Next you need to upload the resulting "kml" file ona webserver, and can have google map point to it. The URL is http://maps.google.com/maps?q=your_kml_url. For example, http://maps.google.com/maps?q=http://marcocorvi.altervista.org/kml/no.kml.

Unfortunately the resolution of the satellite image might too coarse, and you cannot get a full overlay of the cave map with the surface imagery.

DXF export
ESRI export